69 files changed, 2642 insertions, 1681 deletions

diff --git a/crates/ra_arena/src/map.rs b/crates/ra_arena/src/map.rs
index 5e764113d..0f33907c0 100644
--- a/crates/ra_arena/src/map.rs
+++ b/crates/ra_arena/src/map.rs
@@ -14,14 +14,8 @@ pub struct ArenaMap<ID, V> {
 impl<T, V> ArenaMap<Idx<T>, V> {
     pub fn insert(&mut self, id: Idx<T>, t: V) {
         let idx = Self::to_idx(id);
-        if self.v.capacity() <= idx {
-            self.v.reserve(idx + 1 - self.v.capacity());
-        }
-        if self.v.len() <= idx {
-            while self.v.len() <= idx {
-                self.v.push(None);
-            }
-        }
+
+        self.v.resize_with((idx + 1).max(self.v.len()), || None);
         self.v[idx] = Some(t);
     }
 
diff --git a/crates/ra_assists/src/handlers/fill_match_arms.rs b/crates/ra_assists/src/handlers/fill_match_arms.rs
index add82e5b1..8d1af9933 100644
--- a/crates/ra_assists/src/handlers/fill_match_arms.rs
+++ b/crates/ra_assists/src/handlers/fill_match_arms.rs
@@ -1,15 +1,11 @@
-//! FIXME: write short doc here
-
 use std::iter;
 
 use hir::{Adt, HasSource, ModuleDef, Semantics};
 use itertools::Itertools;
 use ra_ide_db::RootDatabase;
+use ra_syntax::ast::{self, make, AstNode, MatchArm, NameOwner, Pat};
 
 use crate::{Assist, AssistCtx, AssistId};
-use ra_syntax::ast::{self, edit::IndentLevel, make, AstNode, NameOwner};
-
-use ast::{MatchArm, Pat};
 
 // Assist: fill_match_arms
 //
@@ -97,10 +93,7 @@ pub(crate) fn fill_match_arms(ctx: AssistCtx) -> Option<Assist> {
     }
 
     ctx.add_assist(AssistId("fill_match_arms"), "Fill match arms", |edit| {
-        arms.extend(missing_arms);
-
-        let indent_level = IndentLevel::from_node(match_arm_list.syntax());
-        let new_arm_list = indent_level.increase_indent(make::match_arm_list(arms));
+        let new_arm_list = match_arm_list.remove_placeholder().append_arms(missing_arms);
 
         edit.target(match_expr.syntax().text_range());
         edit.set_cursor(expr.syntax().text_range().start());
@@ -655,4 +648,93 @@ mod tests {
             "#,
         );
     }
+
+    #[test]
+    fn fill_match_arms_preserves_comments() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match a {
+                    // foo bar baz<|>
+                    A::One => {}
+                    // This is where the rest should be
+                }
+            }
+            "#,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match <|>a {
+                    // foo bar baz
+                    A::One => {}
+                    // This is where the rest should be
+                    A::Two => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_preserves_comments_empty() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match a {
+                    // foo bar baz<|>
+                }
+            }
+            "#,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match <|>a {
+                    // foo bar baz
+                    A::One => {}
+                    A::Two => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_placeholder() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A { One, Two, }
+            fn foo(a: A) {
+                match a<|> {
+                    _ => (),
+                }
+            }
+            "#,
+            r#"
+            enum A { One, Two, }
+            fn foo(a: A) {
+                match <|>a {
+                    A::One => {}
+                    A::Two => {}
+                }
+            }
+            "#,
+        );
+    }
 }
diff --git a/crates/ra_cargo_watch/src/lib.rs b/crates/ra_cargo_watch/src/lib.rs
deleted file mode 100644
index 7c525c430..000000000
--- a/crates/ra_cargo_watch/src/lib.rs
+++ /dev/null
@@ -1,405 +0,0 @@
-//! cargo_check provides the functionality needed to run `cargo check` or
-//! another compatible command (f.x. clippy) in a background thread and provide
-//! LSP diagnostics based on the output of the command.
-use cargo_metadata::Message;
-use crossbeam_channel::{never, select, unbounded, Receiver, RecvError, Sender};
-use lsp_types::{
-    CodeAction, CodeActionOrCommand, Diagnostic, Url, WorkDoneProgress, WorkDoneProgressBegin,
-    WorkDoneProgressEnd, WorkDoneProgressReport,
-};
-use std::{
-    error, fmt,
-    io::{BufRead, BufReader},
-    path::{Path, PathBuf},
-    process::{Command, Stdio},
-    thread::JoinHandle,
-    time::Instant,
-};
-
-mod conv;
-
-use crate::conv::{map_rust_diagnostic_to_lsp, MappedRustDiagnostic};
-
-pub use crate::conv::url_from_path_with_drive_lowercasing;
-
-#[derive(Clone, Debug)]
-pub struct CheckOptions {
-    pub enable: bool,
-    pub args: Vec<String>,
-    pub command: String,
-    pub all_targets: bool,
-}
-
-/// CheckWatcher wraps the shared state and communication machinery used for
-/// running `cargo check` (or other compatible command) and providing
-/// diagnostics based on the output.
-/// The spawned thread is shut down when this struct is dropped.
-#[derive(Debug)]
-pub struct CheckWatcher {
-    pub task_recv: Receiver<CheckTask>,
-    cmd_send: Option<Sender<CheckCommand>>,
-    handle: Option<JoinHandle<()>>,
-}
-
-impl CheckWatcher {
-    pub fn new(options: &CheckOptions, workspace_root: PathBuf) -> CheckWatcher {
-        let options = options.clone();
-
-        let (task_send, task_recv) = unbounded::<CheckTask>();
-        let (cmd_send, cmd_recv) = unbounded::<CheckCommand>();
-        let handle = std::thread::spawn(move || {
-            let mut check = CheckWatcherThread::new(options, workspace_root);
-            check.run(&task_send, &cmd_recv);
-        });
-        CheckWatcher { task_recv, cmd_send: Some(cmd_send), handle: Some(handle) }
-    }
-
-    /// Returns a CheckWatcher that doesn't actually do anything
-    pub fn dummy() -> CheckWatcher {
-        CheckWatcher { task_recv: never(), cmd_send: None, handle: None }
-    }
-
-    /// Schedule a re-start of the cargo check worker.
-    pub fn update(&self) {
-        if let Some(cmd_send) = &self.cmd_send {
-            cmd_send.send(CheckCommand::Update).unwrap();
-        }
-    }
-}
-
-impl std::ops::Drop for CheckWatcher {
-    fn drop(&mut self) {
-        if let Some(handle) = self.handle.take() {
-            // Take the sender out of the option
-            let cmd_send = self.cmd_send.take();
-
-            // Dropping the sender finishes the thread loop
-            drop(cmd_send);
-
-            // Join the thread, it should finish shortly. We don't really care
-            // whether it panicked, so it is safe to ignore the result
-            let _ = handle.join();
-        }
-    }
-}
-
-#[derive(Debug)]
-pub enum CheckTask {
-    /// Request a clearing of all cached diagnostics from the check watcher
-    ClearDiagnostics,
-
-    /// Request adding a diagnostic with fixes included to a file
-    AddDiagnostic { url: Url, diagnostic: Diagnostic, fixes: Vec<CodeActionOrCommand> },
-
-    /// Request check progress notification to client
-    Status(WorkDoneProgress),
-}
-
-pub enum CheckCommand {
-    /// Request re-start of check thread
-    Update,
-}
-
-struct CheckWatcherThread {
-    options: CheckOptions,
-    workspace_root: PathBuf,
-    watcher: WatchThread,
-    last_update_req: Option<Instant>,
-}
-
-impl CheckWatcherThread {
-    fn new(options: CheckOptions, workspace_root: PathBuf) -> CheckWatcherThread {
-        CheckWatcherThread {
-            options,
-            workspace_root,
-            watcher: WatchThread::dummy(),
-            last_update_req: None,
-        }
-    }
-
-    fn run(&mut self, task_send: &Sender<CheckTask>, cmd_recv: &Receiver<CheckCommand>) {
-        loop {
-            select! {
-                recv(&cmd_recv) -> cmd => match cmd {
-                    Ok(cmd) => self.handle_command(cmd),
-                    Err(RecvError) => {
-                        // Command channel has closed, so shut down
-                        break;
-                    },
-                },
-                recv(self.watcher.message_recv) -> msg => match msg {
-                    Ok(msg) => self.handle_message(msg, task_send),
-                    Err(RecvError) => {
-                        // Watcher finished, replace it with a never channel to
-                        // avoid busy-waiting.
-                        std::mem::replace(&mut self.watcher.message_recv, never());
-                    },
-                }
-            };
-
-            if self.should_recheck() {
-                self.last_update_req.take();
-                task_send.send(CheckTask::ClearDiagnostics).unwrap();
-
-                // Replace with a dummy watcher first so we drop the original and wait for completion
-                std::mem::replace(&mut self.watcher, WatchThread::dummy());
-
-                // Then create the actual new watcher
-                self.watcher = WatchThread::new(&self.options, &self.workspace_root);
-            }
-        }
-    }
-
-    fn should_recheck(&mut self) -> bool {
-        if let Some(_last_update_req) = &self.last_update_req {
-            // We currently only request an update on save, as we need up to
-            // date source on disk for cargo check to do it's magic, so we
-            // don't really need to debounce the requests at this point.
-            return true;
-        }
-        false
-    }
-
-    fn handle_command(&mut self, cmd: CheckCommand) {
-        match cmd {
-            CheckCommand::Update => self.last_update_req = Some(Instant::now()),
-        }
-    }
-
-    fn handle_message(&self, msg: CheckEvent, task_send: &Sender<CheckTask>) {
-        match msg {
-            CheckEvent::Begin => {
-                task_send
-                    .send(CheckTask::Status(WorkDoneProgress::Begin(WorkDoneProgressBegin {
-                        title: "Running 'cargo check'".to_string(),
-                        cancellable: Some(false),
-                        message: None,
-                        percentage: None,
-                    })))
-                    .unwrap();
-            }
-
-            CheckEvent::End => {
-                task_send
-                    .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd {
-                        message: None,
-                    })))
-                    .unwrap();
-            }
-
-            CheckEvent::Msg(Message::CompilerArtifact(msg)) => {
-                task_send
-                    .send(CheckTask::Status(WorkDoneProgress::Report(WorkDoneProgressReport {
-                        cancellable: Some(false),
-                        message: Some(msg.target.name),
-                        percentage: None,
-                    })))
-                    .unwrap();
-            }
-
-            CheckEvent::Msg(Message::CompilerMessage(msg)) => {
-                let map_result = map_rust_diagnostic_to_lsp(&msg.message, &self.workspace_root);
-                if map_result.is_empty() {
-                    return;
-                }
-
-                for MappedRustDiagnostic { location, diagnostic, fixes } in map_result {
-                    let fixes = fixes
-                        .into_iter()
-                        .map(|fix| {
-                            CodeAction { diagnostics: Some(vec![diagnostic.clone()]), ..fix }.into()
-                        })
-                        .collect();
-
-                    task_send
-                        .send(CheckTask::AddDiagnostic { url: location.uri, diagnostic, fixes })
-                        .unwrap();
-                }
-            }
-
-            CheckEvent::Msg(Message::BuildScriptExecuted(_msg)) => {}
-            CheckEvent::Msg(Message::Unknown) => {}
-        }
-    }
-}
-
-#[derive(Debug)]
-pub struct DiagnosticWithFixes {
-    diagnostic: Diagnostic,
-    fixes: Vec<CodeAction>,
-}
-
-/// WatchThread exists to wrap around the communication needed to be able to
-/// run `cargo check` without blocking. Currently the Rust standard library
-/// doesn't provide a way to read sub-process output without blocking, so we
-/// have to wrap sub-processes output handling in a thread and pass messages
-/// back over a channel.
-/// The correct way to dispose of the thread is to drop it, on which the
-/// sub-process will be killed, and the thread will be joined.
-struct WatchThread {
-    handle: Option<JoinHandle<()>>,
-    message_recv: Receiver<CheckEvent>,
-}
-
-enum CheckEvent {
-    Begin,
-    Msg(cargo_metadata::Message),
-    End,
-}
-
-#[derive(Debug)]
-pub struct CargoError(String);
-
-impl fmt::Display for CargoError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Cargo failed: {}", self.0)
-    }
-}
-impl error::Error for CargoError {}
-
-pub fn run_cargo(
-    args: &[String],
-    current_dir: Option<&Path>,
-    on_message: &mut dyn FnMut(cargo_metadata::Message) -> bool,
-) -> Result<(), CargoError> {
-    let mut command = Command::new("cargo");
-    if let Some(current_dir) = current_dir {
-        command.current_dir(current_dir);
-    }
-
-    let mut child = command
-        .args(args)
-        .stdout(Stdio::piped())
-        .stderr(Stdio::null())
-        .stdin(Stdio::null())
-        .spawn()
-        .expect("couldn't launch cargo");
-
-    // We manually read a line at a time, instead of using serde's
-    // stream deserializers, because the deserializer cannot recover
-    // from an error, resulting in it getting stuck, because we try to
-    // be resillient against failures.
-    //
-    // Because cargo only outputs one JSON object per line, we can
-    // simply skip a line if it doesn't parse, which just ignores any
-    // erroneus output.
-    let stdout = BufReader::new(child.stdout.take().unwrap());
-    let mut read_at_least_one_message = false;
-
-    for line in stdout.lines() {
-        let line = match line {
-            Ok(line) => line,
-            Err(err) => {
-                log::error!("Couldn't read line from cargo: {}", err);
-                continue;
-            }
-        };
-
-        let message = serde_json::from_str::<cargo_metadata::Message>(&line);
-        let message = match message {
-            Ok(message) => message,
-            Err(err) => {
-                log::error!("Invalid json from cargo check, ignoring ({}): {:?} ", err, line);
-                continue;
-            }
-        };
-
-        read_at_least_one_message = true;
-
-        if !on_message(message) {
-            break;
-        }
-    }
-
-    // It is okay to ignore the result, as it only errors if the process is already dead
-    let _ = child.kill();
-
-    let err_msg = match child.wait() {
-        Ok(exit_code) if !exit_code.success() && !read_at_least_one_message => {
-            // FIXME: Read the stderr to display the reason, see `read2()` reference in PR comment:
-            // https://github.com/rust-analyzer/rust-analyzer/pull/3632#discussion_r395605298
-            format!(
-                "the command produced no valid metadata (exit code: {:?}): cargo {}",
-                exit_code,
-                args.join(" ")
-            )
-        }
-        Err(err) => format!("io error: {:?}", err),
-        Ok(_) => return Ok(()),
-    };
-
-    Err(CargoError(err_msg))
-}
-
-impl WatchThread {
-    fn dummy() -> WatchThread {
-        WatchThread { handle: None, message_recv: never() }
-    }
-
-    fn new(options: &CheckOptions, workspace_root: &Path) -> WatchThread {
-        let mut args: Vec<String> = vec![
-            options.command.clone(),
-            "--workspace".to_string(),
-            "--message-format=json".to_string(),
-            "--manifest-path".to_string(),
-            format!("{}/Cargo.toml", workspace_root.display()),
-        ];
-        if options.all_targets {
-            args.push("--all-targets".to_string());
-        }
-        args.extend(options.args.iter().cloned());
-
-        let (message_send, message_recv) = unbounded();
-        let workspace_root = workspace_root.to_owned();
-        let handle = if options.enable {
-            Some(std::thread::spawn(move || {
-                // If we trigger an error here, we will do so in the loop instead,
-                // which will break out of the loop, and continue the shutdown
-                let _ = message_send.send(CheckEvent::Begin);
-
-                let res = run_cargo(&args, Some(&workspace_root), &mut |message| {
-                    // Skip certain kinds of messages to only spend time on what's useful
-                    match &message {
-                        Message::CompilerArtifact(artifact) if artifact.fresh => return true,
-                        Message::BuildScriptExecuted(_) => return true,
-                        Message::Unknown => return true,
-                        _ => {}
-                    }
-
-                    // if the send channel was closed, we want to shutdown
-                    message_send.send(CheckEvent::Msg(message)).is_ok()
-                });
-
-                if let Err(err) = res {
-                    // FIXME: make the `message_send` to be `Sender<Result<CheckEvent, CargoError>>`
-                    // to display user-caused misconfiguration errors instead of just logging them here
-                    log::error!("Cargo watcher failed {:?}", err);
-                }
-
-                // We can ignore any error here, as we are already in the progress
-                // of shutting down.
-                let _ = message_send.send(CheckEvent::End);
-            }))
-        } else {
-            None
-        };
-        WatchThread { handle, message_recv }
-    }
-}
-
-impl std::ops::Drop for WatchThread {
-    fn drop(&mut self) {
-        if let Some(handle) = self.handle.take() {
-            // Replace our reciever with dummy one, so we can drop and close the
-            // one actually communicating with the thread
-            let recv = std::mem::replace(&mut self.message_recv, never());
-
-            // Dropping the original reciever initiates thread sub-process shutdown
-            drop(recv);
-
-            // Join the thread, it should finish shortly. We don't really care
-            // whether it panicked, so it is safe to ignore the result
-            let _ = handle.join();
-        }
-    }
-}
diff --git a/crates/ra_cargo_watch/Cargo.toml b/crates/ra_flycheck/Cargo.toml
index 741345a21..c9a9ddc12 100644
--- a/crates/ra_cargo_watch/Cargo.toml
+++ b/crates/ra_flycheck/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 edition = "2018"
-name = "ra_cargo_watch"
+name = "ra_flycheck"
 version = "0.1.0"
 authors = ["rust-analyzer developers"]
 
@@ -10,6 +10,7 @@ lsp-types = { version = "0.73.0", features = ["proposed"] }
 log = "0.4.8"
 cargo_metadata = "0.9.1"
 serde_json = "1.0.48"
+jod-thread = "0.1.1"
 
 [dev-dependencies]
 insta = "0.15.0"
diff --git a/crates/ra_cargo_watch/src/conv.rs b/crates/ra_flycheck/src/conv.rs
index 817543deb..817543deb 100644
--- a/crates/ra_cargo_watch/src/conv.rs
+++ b/crates/ra_flycheck/src/conv.rs
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_clippy_pass_by_ref.snap
index a59fa84fa..4c9db0385 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_clippy_pass_by_ref.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_handles_macro_location.snap
index 61ae0c9ae..7cde4d867 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_handles_macro_location.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_macro_compiler_error.snap
index 641da1a58..1cc37e087 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_macro_compiler_error.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_multi_line_fix.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_multi_line_fix.snap
index 0557a2e79..615ed8378 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_multi_line_fix.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_multi_line_fix.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_incompatible_type_for_trait.snap
index 754bc33a4..0df0fce18 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_incompatible_type_for_trait.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_mismatched_type.snap
index 78b7f7cc8..28ebcb3b3 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_mismatched_type.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_unused_variable.snap
index 5989ed202..5e0873281 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_unused_variable.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_wrong_number_of_parameters.snap
index e34b546dc..e500d3cd6 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap
+++ b/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_wrong_number_of_parameters.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_cargo_watch/src/conv/test.rs
+source: crates/ra_flycheck/src/conv/test.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_cargo_watch/src/conv/test.rs b/crates/ra_flycheck/src/conv/test.rs
index 4e81455ca..4e81455ca 100644
--- a/crates/ra_cargo_watch/src/conv/test.rs
+++ b/crates/ra_flycheck/src/conv/test.rs
diff --git a/crates/ra_flycheck/src/lib.rs b/crates/ra_flycheck/src/lib.rs
new file mode 100644
index 000000000..b54a30ab8
--- /dev/null
+++ b/crates/ra_flycheck/src/lib.rs
@@ -0,0 +1,340 @@
+//! cargo_check provides the functionality needed to run `cargo check` or
+//! another compatible command (f.x. clippy) in a background thread and provide
+//! LSP diagnostics based on the output of the command.
+mod conv;
+
+use std::{
+    env,
+    io::{self, BufRead, BufReader},
+    path::PathBuf,
+    process::{Command, Stdio},
+    time::Instant,
+};
+
+use cargo_metadata::Message;
+use crossbeam_channel::{never, select, unbounded, Receiver, RecvError, Sender};
+use lsp_types::{
+    CodeAction, CodeActionOrCommand, Diagnostic, Url, WorkDoneProgress, WorkDoneProgressBegin,
+    WorkDoneProgressEnd, WorkDoneProgressReport,
+};
+
+use crate::conv::{map_rust_diagnostic_to_lsp, MappedRustDiagnostic};
+
+pub use crate::conv::url_from_path_with_drive_lowercasing;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum FlycheckConfig {
+    CargoCommand { command: String, all_targets: bool, extra_args: Vec<String> },
+    CustomCommand { command: String, args: Vec<String> },
+}
+
+/// Flycheck wraps the shared state and communication machinery used for
+/// running `cargo check` (or other compatible command) and providing
+/// diagnostics based on the output.
+/// The spawned thread is shut down when this struct is dropped.
+#[derive(Debug)]
+pub struct Flycheck {
+    // XXX: drop order is significant
+    cmd_send: Sender<CheckCommand>,
+    handle: jod_thread::JoinHandle<()>,
+    pub task_recv: Receiver<CheckTask>,
+}
+
+impl Flycheck {
+    pub fn new(config: FlycheckConfig, workspace_root: PathBuf) -> Flycheck {
+        let (task_send, task_recv) = unbounded::<CheckTask>();
+        let (cmd_send, cmd_recv) = unbounded::<CheckCommand>();
+        let handle = jod_thread::spawn(move || {
+            FlycheckThread::new(config, workspace_root).run(&task_send, &cmd_recv);
+        });
+        Flycheck { task_recv, cmd_send, handle }
+    }
+
+    /// Schedule a re-start of the cargo check worker.
+    pub fn update(&self) {
+        self.cmd_send.send(CheckCommand::Update).unwrap();
+    }
+}
+
+#[derive(Debug)]
+pub enum CheckTask {
+    /// Request a clearing of all cached diagnostics from the check watcher
+    ClearDiagnostics,
+
+    /// Request adding a diagnostic with fixes included to a file
+    AddDiagnostic { url: Url, diagnostic: Diagnostic, fixes: Vec<CodeActionOrCommand> },
+
+    /// Request check progress notification to client
+    Status(WorkDoneProgress),
+}
+
+pub enum CheckCommand {
+    /// Request re-start of check thread
+    Update,
+}
+
+struct FlycheckThread {
+    config: FlycheckConfig,
+    workspace_root: PathBuf,
+    last_update_req: Option<Instant>,
+    // XXX: drop order is significant
+    message_recv: Receiver<CheckEvent>,
+    /// WatchThread exists to wrap around the communication needed to be able to
+    /// run `cargo check` without blocking. Currently the Rust standard library
+    /// doesn't provide a way to read sub-process output without blocking, so we
+    /// have to wrap sub-processes output handling in a thread and pass messages
+    /// back over a channel.
+    check_process: Option<jod_thread::JoinHandle<()>>,
+}
+
+impl FlycheckThread {
+    fn new(config: FlycheckConfig, workspace_root: PathBuf) -> FlycheckThread {
+        FlycheckThread {
+            config,
+            workspace_root,
+            last_update_req: None,
+            message_recv: never(),
+            check_process: None,
+        }
+    }
+
+    fn run(&mut self, task_send: &Sender<CheckTask>, cmd_recv: &Receiver<CheckCommand>) {
+        // If we rerun the thread, we need to discard the previous check results first
+        self.clean_previous_results(task_send);
+
+        loop {
+            select! {
+                recv(&cmd_recv) -> cmd => match cmd {
+                    Ok(cmd) => self.handle_command(cmd),
+                    Err(RecvError) => {
+                        // Command channel has closed, so shut down
+                        break;
+                    },
+                },
+                recv(self.message_recv) -> msg => match msg {
+                    Ok(msg) => self.handle_message(msg, task_send),
+                    Err(RecvError) => {
+                        // Watcher finished, replace it with a never channel to
+                        // avoid busy-waiting.
+                        self.message_recv = never();
+                        self.check_process = None;
+                    },
+                }
+            };
+
+            if self.should_recheck() {
+                self.last_update_req = None;
+                task_send.send(CheckTask::ClearDiagnostics).unwrap();
+                self.restart_check_process();
+            }
+        }
+    }
+
+    fn clean_previous_results(&self, task_send: &Sender<CheckTask>) {
+        task_send.send(CheckTask::ClearDiagnostics).unwrap();
+        task_send
+            .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd { message: None })))
+            .unwrap();
+    }
+
+    fn should_recheck(&mut self) -> bool {
+        if let Some(_last_update_req) = &self.last_update_req {
+            // We currently only request an update on save, as we need up to
+            // date source on disk for cargo check to do it's magic, so we
+            // don't really need to debounce the requests at this point.
+            return true;
+        }
+        false
+    }
+
+    fn handle_command(&mut self, cmd: CheckCommand) {
+        match cmd {
+            CheckCommand::Update => self.last_update_req = Some(Instant::now()),
+        }
+    }
+
+    fn handle_message(&self, msg: CheckEvent, task_send: &Sender<CheckTask>) {
+        match msg {
+            CheckEvent::Begin => {
+                task_send
+                    .send(CheckTask::Status(WorkDoneProgress::Begin(WorkDoneProgressBegin {
+                        title: "Running 'cargo check'".to_string(),
+                        cancellable: Some(false),
+                        message: None,
+                        percentage: None,
+                    })))
+                    .unwrap();
+            }
+
+            CheckEvent::End => {
+                task_send
+                    .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd {
+                        message: None,
+                    })))
+                    .unwrap();
+            }
+
+            CheckEvent::Msg(Message::CompilerArtifact(msg)) => {
+                task_send
+                    .send(CheckTask::Status(WorkDoneProgress::Report(WorkDoneProgressReport {
+                        cancellable: Some(false),
+                        message: Some(msg.target.name),
+                        percentage: None,
+                    })))
+                    .unwrap();
+            }
+
+            CheckEvent::Msg(Message::CompilerMessage(msg)) => {
+                let map_result = map_rust_diagnostic_to_lsp(&msg.message, &self.workspace_root);
+                if map_result.is_empty() {
+                    return;
+                }
+
+                for MappedRustDiagnostic { location, diagnostic, fixes } in map_result {
+                    let fixes = fixes
+                        .into_iter()
+                        .map(|fix| {
+                            CodeAction { diagnostics: Some(vec![diagnostic.clone()]), ..fix }.into()
+                        })
+                        .collect();
+
+                    task_send
+                        .send(CheckTask::AddDiagnostic { url: location.uri, diagnostic, fixes })
+                        .unwrap();
+                }
+            }
+
+            CheckEvent::Msg(Message::BuildScriptExecuted(_msg)) => {}
+            CheckEvent::Msg(Message::Unknown) => {}
+        }
+    }
+
+    fn restart_check_process(&mut self) {
+        // First, clear and cancel the old thread
+        self.message_recv = never();
+        self.check_process = None;
+
+        let mut cmd = match &self.config {
+            FlycheckConfig::CargoCommand { command, all_targets, extra_args } => {
+                let mut cmd = Command::new(cargo_binary());
+                cmd.arg(command);
+                cmd.args(&["--workspace", "--message-format=json", "--manifest-path"]);
+                cmd.arg(self.workspace_root.join("Cargo.toml"));
+                if *all_targets {
+                    cmd.arg("--all-targets");
+                }
+                cmd.args(extra_args);
+                cmd
+            }
+            FlycheckConfig::CustomCommand { command, args } => {
+                let mut cmd = Command::new(command);
+                cmd.args(args);
+                cmd
+            }
+        };
+        cmd.current_dir(&self.workspace_root);
+
+        let (message_send, message_recv) = unbounded();
+        self.message_recv = message_recv;
+        self.check_process = Some(jod_thread::spawn(move || {
+            // If we trigger an error here, we will do so in the loop instead,
+            // which will break out of the loop, and continue the shutdown
+            let _ = message_send.send(CheckEvent::Begin);
+
+            let res = run_cargo(cmd, &mut |message| {
+                // Skip certain kinds of messages to only spend time on what's useful
+                match &message {
+                    Message::CompilerArtifact(artifact) if artifact.fresh => return true,
+                    Message::BuildScriptExecuted(_) => return true,
+                    Message::Unknown => return true,
+                    _ => {}
+                }
+
+                // if the send channel was closed, we want to shutdown
+                message_send.send(CheckEvent::Msg(message)).is_ok()
+            });
+
+            if let Err(err) = res {
+                // FIXME: make the `message_send` to be `Sender<Result<CheckEvent, CargoError>>`
+                // to display user-caused misconfiguration errors instead of just logging them here
+                log::error!("Cargo watcher failed {:?}", err);
+            }
+
+            // We can ignore any error here, as we are already in the progress
+            // of shutting down.
+            let _ = message_send.send(CheckEvent::End);
+        }))
+    }
+}
+
+#[derive(Debug)]
+pub struct DiagnosticWithFixes {
+    diagnostic: Diagnostic,
+    fixes: Vec<CodeAction>,
+}
+
+enum CheckEvent {
+    Begin,
+    Msg(cargo_metadata::Message),
+    End,
+}
+
+fn run_cargo(
+    mut command: Command,
+    on_message: &mut dyn FnMut(cargo_metadata::Message) -> bool,
+) -> io::Result<()> {
+    let mut child =
+        command.stdout(Stdio::piped()).stderr(Stdio::null()).stdin(Stdio::null()).spawn()?;
+
+    // We manually read a line at a time, instead of using serde's
+    // stream deserializers, because the deserializer cannot recover
+    // from an error, resulting in it getting stuck, because we try to
+    // be resillient against failures.
+    //
+    // Because cargo only outputs one JSON object per line, we can
+    // simply skip a line if it doesn't parse, which just ignores any
+    // erroneus output.
+    let stdout = BufReader::new(child.stdout.take().unwrap());
+    let mut read_at_least_one_message = false;
+
+    for line in stdout.lines() {
+        let line = line?;
+
+        let message = serde_json::from_str::<cargo_metadata::Message>(&line);
+        let message = match message {
+            Ok(message) => message,
+            Err(err) => {
+                log::error!("Invalid json from cargo check, ignoring ({}): {:?} ", err, line);
+                continue;
+            }
+        };
+
+        read_at_least_one_message = true;
+
+        if !on_message(message) {
+            break;
+        }
+    }
+
+    // It is okay to ignore the result, as it only errors if the process is already dead
+    let _ = child.kill();
+
+    let exit_status = child.wait()?;
+    if !exit_status.success() && !read_at_least_one_message {
+        // FIXME: Read the stderr to display the reason, see `read2()` reference in PR comment:
+        // https://github.com/rust-analyzer/rust-analyzer/pull/3632#discussion_r395605298
+        return Err(io::Error::new(
+            io::ErrorKind::Other,
+            format!(
+                "the command produced no valid metadata (exit code: {:?}): {:?}",
+                exit_status, command
+            ),
+        ));
+    }
+
+    Ok(())
+}
+
+fn cargo_binary() -> String {
+    env::var("CARGO").unwrap_or_else(|_| "cargo".to_string())
+}
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index e8443dde8..28c570c76 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -417,26 +417,7 @@ impl ExprCollector<'_> {
                 }
             }
 
-            ast::Expr::Literal(e) => {
-                let lit = match e.kind() {
-                    LiteralKind::IntNumber { suffix } => {
-                        let known_name = suffix.and_then(|it| BuiltinInt::from_suffix(&it));
-
-                        Literal::Int(Default::default(), known_name)
-                    }
-                    LiteralKind::FloatNumber { suffix } => {
-                        let known_name = suffix.and_then(|it| BuiltinFloat::from_suffix(&it));
-
-                        Literal::Float(Default::default(), known_name)
-                    }
-                    LiteralKind::ByteString => Literal::ByteString(Default::default()),
-                    LiteralKind::String => Literal::String(Default::default()),
-                    LiteralKind::Byte => Literal::Int(Default::default(), Some(BuiltinInt::U8)),
-                    LiteralKind::Bool => Literal::Bool(Default::default()),
-                    LiteralKind::Char => Literal::Char(Default::default()),
-                };
-                self.alloc_expr(Expr::Literal(lit), syntax_ptr)
-            }
+            ast::Expr::Literal(e) => self.alloc_expr(Expr::Literal(e.kind().into()), syntax_ptr),
             ast::Expr::IndexExpr(e) => {
                 let base = self.collect_expr_opt(e.base());
                 let index = self.collect_expr_opt(e.index());
@@ -679,10 +660,19 @@ impl ExprCollector<'_> {
                     suffix: suffix.into_iter().map(|p| self.collect_pat(p)).collect(),
                 }
             }
+            ast::Pat::LiteralPat(lit) => {
+                if let Some(ast_lit) = lit.literal() {
+                    let expr = Expr::Literal(ast_lit.kind().into());
+                    let expr_ptr = AstPtr::new(&ast::Expr::Literal(ast_lit));
+                    let expr_id = self.alloc_expr(expr, expr_ptr);
+                    Pat::Lit(expr_id)
+                } else {
+                    Pat::Missing
+                }
+            }
 
             // FIXME: implement
             ast::Pat::BoxPat(_) => Pat::Missing,
-            ast::Pat::LiteralPat(_) => Pat::Missing,
             ast::Pat::RangePat(_) => Pat::Missing,
         };
         let ptr = AstPtr::new(&pat);
@@ -741,3 +731,25 @@ impl From<ast::BinOp> for BinaryOp {
         }
     }
 }
+
+impl From<ast::LiteralKind> for Literal {
+    fn from(ast_lit_kind: ast::LiteralKind) -> Self {
+        match ast_lit_kind {
+            LiteralKind::IntNumber { suffix } => {
+                let known_name = suffix.and_then(|it| BuiltinInt::from_suffix(&it));
+
+                Literal::Int(Default::default(), known_name)
+            }
+            LiteralKind::FloatNumber { suffix } => {
+                let known_name = suffix.and_then(|it| BuiltinFloat::from_suffix(&it));
+
+                Literal::Float(Default::default(), known_name)
+            }
+            LiteralKind::ByteString => Literal::ByteString(Default::default()),
+            LiteralKind::String => Literal::String(Default::default()),
+            LiteralKind::Byte => Literal::Int(Default::default(), Some(BuiltinInt::U8)),
+            LiteralKind::Bool(val) => Literal::Bool(val),
+            LiteralKind::Char => Literal::Char(Default::default()),
+        }
+    }
+}
diff --git a/crates/ra_hir_expand/src/proc_macro.rs b/crates/ra_hir_expand/src/proc_macro.rs
index 4d270e0de..97d1208ec 100644
--- a/crates/ra_hir_expand/src/proc_macro.rs
+++ b/crates/ra_hir_expand/src/proc_macro.rs
@@ -9,6 +9,15 @@ pub struct ProcMacroExpander {
     proc_macro_id: ProcMacroId,
 }
 
+macro_rules! err {
+    ($fmt:literal, $($tt:tt),*) => {
+        mbe::ExpandError::ProcMacroError(tt::ExpansionError::Unknown(format!($fmt, $($tt),*)))
+    };
+    ($fmt:literal) => {
+        mbe::ExpandError::ProcMacroError(tt::ExpansionError::Unknown($fmt.to_string()))
+    }
+}
+
 impl ProcMacroExpander {
     pub fn new(krate: CrateId, proc_macro_id: ProcMacroId) -> ProcMacroExpander {
         ProcMacroExpander { krate, proc_macro_id }
@@ -25,8 +34,24 @@ impl ProcMacroExpander {
             .proc_macro
             .get(self.proc_macro_id.0 as usize)
             .clone()
-            .ok_or_else(|| mbe::ExpandError::ConversionError)?;
+            .ok_or_else(|| err!("No derive macro found."))?;
+
+        let tt = remove_derive_atr(tt, &proc_macro.name)
+            .ok_or_else(|| err!("Fail to remove derive for custom derive"))?;
 
         proc_macro.expander.expand(&tt, None).map_err(mbe::ExpandError::from)
     }
 }
+
+fn remove_derive_atr(tt: &tt::Subtree, _name: &str) -> Option<tt::Subtree> {
+    // FIXME: proper handle the remove derive
+    // We assume the first 2 tokens are #[derive(name)]
+    if tt.token_trees.len() > 2 {
+        let mut tt = tt.clone();
+        tt.token_trees.remove(0);
+        tt.token_trees.remove(0);
+        return Some(tt);
+    }
+
+    None
+}
diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index a6ef44a31..13ecd537a 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -159,20 +159,13 @@ impl HirDisplay for ApplicationTy {
             }
             TypeCtor::FnDef(def) => {
                 let sig = f.db.callable_item_signature(def).subst(&self.parameters);
-                let name = match def {
-                    CallableDef::FunctionId(ff) => f.db.function_data(ff).name.clone(),
-                    CallableDef::StructId(s) => f.db.struct_data(s).name.clone(),
+                match def {
+                    CallableDef::FunctionId(ff) => write!(f, "fn {}", f.db.function_data(ff).name)?,
+                    CallableDef::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
                     CallableDef::EnumVariantId(e) => {
-                        let enum_data = f.db.enum_data(e.parent);
-                        enum_data.variants[e.local_id].name.clone()
+                        write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
                     }
                 };
-                match def {
-                    CallableDef::FunctionId(_) => write!(f, "fn {}", name)?,
-                    CallableDef::StructId(_) | CallableDef::EnumVariantId(_) => {
-                        write!(f, "{}", name)?
-                    }
-                }
                 if self.parameters.len() > 0 {
                     let generics = generics(f.db.upcast(), def.into());
                     let (parent_params, self_param, type_params, _impl_trait_params) =
@@ -197,8 +190,6 @@ impl HirDisplay for ApplicationTy {
                 };
                 write!(f, "{}", name)?;
                 if self.parameters.len() > 0 {
-                    write!(f, "<")?;
-
                     let mut non_default_parameters = Vec::with_capacity(self.parameters.len());
                     let parameters_to_write = if f.omit_verbose_types() {
                         match self
@@ -207,8 +198,8 @@ impl HirDisplay for ApplicationTy {
                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
                             .filter(|defaults| !defaults.is_empty())
                         {
-                            Option::None => self.parameters.0.as_ref(),
-                            Option::Some(default_parameters) => {
+                            None => self.parameters.0.as_ref(),
+                            Some(default_parameters) => {
                                 for (i, parameter) in self.parameters.iter().enumerate() {
                                     match (parameter, default_parameters.get(i)) {
                                         (&Ty::Unknown, _) | (_, None) => {
@@ -228,7 +219,7 @@ impl HirDisplay for ApplicationTy {
                     } else {
                         self.parameters.0.as_ref()
                     };
-
+                    write!(f, "<")?;
                     f.write_joined(parameters_to_write, ", ")?;
                     write!(f, ">")?;
                 }
@@ -238,9 +229,9 @@ impl HirDisplay for ApplicationTy {
                     AssocContainerId::TraitId(it) => it,
                     _ => panic!("not an associated type"),
                 };
-                let trait_name = f.db.trait_data(trait_).name.clone();
-                let name = f.db.type_alias_data(type_alias).name.clone();
-                write!(f, "{}::{}", trait_name, name)?;
+                let trait_ = f.db.trait_data(trait_);
+                let type_alias = f.db.type_alias_data(type_alias);
+                write!(f, "{}::{}", trait_.name, type_alias.name)?;
                 if self.parameters.len() > 0 {
                     write!(f, "<")?;
                     f.write_joined(&*self.parameters.0, ", ")?;
@@ -273,8 +264,8 @@ impl HirDisplay for ProjectionTy {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
-        let trait_name = f.db.trait_data(self.trait_(f.db)).name.clone();
-        write!(f, "<{} as {}", self.parameters[0].display(f.db), trait_name,)?;
+        let trait_ = f.db.trait_data(self.trait_(f.db));
+        write!(f, "<{} as {}", self.parameters[0].display(f.db), trait_.name)?;
         if self.parameters.len() > 1 {
             write!(f, "<")?;
             f.write_joined(&self.parameters[1..], ", ")?;
@@ -319,7 +310,7 @@ impl HirDisplay for Ty {
                     Ty::Opaque(_) => write!(f, "impl ")?,
                     _ => unreachable!(),
                 };
-                write_bounds_like_dyn_trait(&predicates, f)?;
+                write_bounds_like_dyn_trait(predicates, f)?;
             }
             Ty::Unknown => write!(f, "{{unknown}}")?,
             Ty::Infer(..) => write!(f, "_")?,
@@ -352,7 +343,7 @@ fn write_bounds_like_dyn_trait(
                 // We assume that the self type is $0 (i.e. the
                 // existential) here, which is the only thing that's
                 // possible in actual Rust, and hence don't print it
-                write!(f, "{}", f.db.trait_data(trait_ref.trait_).name.clone())?;
+                write!(f, "{}", f.db.trait_data(trait_ref.trait_).name)?;
                 if trait_ref.substs.len() > 1 {
                     write!(f, "<")?;
                     f.write_joined(&trait_ref.substs[1..], ", ")?;
@@ -369,9 +360,8 @@ fn write_bounds_like_dyn_trait(
                     write!(f, "<")?;
                     angle_open = true;
                 }
-                let name =
-                    f.db.type_alias_data(projection_pred.projection_ty.associated_ty).name.clone();
-                write!(f, "{} = ", name)?;
+                let type_alias = f.db.type_alias_data(projection_pred.projection_ty.associated_ty);
+                write!(f, "{} = ", type_alias.name)?;
                 projection_pred.ty.hir_fmt(f)?;
             }
             GenericPredicate::Error => {
@@ -405,7 +395,7 @@ impl TraitRef {
         } else {
             write!(f, ": ")?;
         }
-        write!(f, "{}", f.db.trait_data(self.trait_).name.clone())?;
+        write!(f, "{}", f.db.trait_data(self.trait_).name)?;
         if self.substs.len() > 1 {
             write!(f, "<")?;
             f.write_joined(&self.substs[1..], ", ")?;
diff --git a/crates/ra_hir_ty/src/infer/pat.rs b/crates/ra_hir_ty/src/infer/pat.rs
index baed6225b..86acd27f8 100644
--- a/crates/ra_hir_ty/src/infer/pat.rs
+++ b/crates/ra_hir_ty/src/infer/pat.rs
@@ -11,7 +11,7 @@ use hir_def::{
 use hir_expand::name::Name;
 use test_utils::tested_by;
 
-use super::{BindingMode, InferenceContext};
+use super::{BindingMode, Expectation, InferenceContext};
 use crate::{utils::variant_data, Substs, Ty, TypeCtor};
 
 impl<'a> InferenceContext<'a> {
@@ -198,7 +198,14 @@ impl<'a> InferenceContext<'a> {
 
                 Ty::apply_one(container_ty, elem_ty)
             }
-            _ => Ty::Unknown,
+            Pat::Wild => expected.clone(),
+            Pat::Range { start, end } => {
+                let start_ty = self.infer_expr(*start, &Expectation::has_type(expected.clone()));
+                let end_ty = self.infer_expr(*end, &Expectation::has_type(start_ty));
+                end_ty
+            }
+            Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
+            Pat::Missing => Ty::Unknown,
         };
         // use a new type variable if we got Ty::Unknown here
         let ty = self.insert_type_vars_shallow(ty);
diff --git a/crates/ra_hir_ty/src/tests/coercion.rs b/crates/ra_hir_ty/src/tests/coercion.rs
index 1e303f5ce..3e3d55c04 100644
--- a/crates/ra_hir_ty/src/tests/coercion.rs
+++ b/crates/ra_hir_ty/src/tests/coercion.rs
@@ -275,12 +275,14 @@ fn test(i: i32) {
     [70; 147) 'match ...     }': &[i32]
     [76; 77) 'i': i32
     [88; 89) '2': i32
+    [88; 89) '2': i32
     [93; 96) 'foo': fn foo<i32>(&[i32]) -> &[i32]
     [93; 102) 'foo(&[2])': &[i32]
     [97; 101) '&[2]': &[i32; _]
     [98; 101) '[2]': [i32; _]
     [99; 100) '2': i32
     [112; 113) '1': i32
+    [112; 113) '1': i32
     [117; 121) '&[1]': &[i32; _]
     [118; 121) '[1]': [i32; _]
     [119; 120) '1': i32
@@ -316,10 +318,12 @@ fn test(i: i32) {
     [70; 147) 'match ...     }': &[i32]
     [76; 77) 'i': i32
     [88; 89) '1': i32
+    [88; 89) '1': i32
     [93; 97) '&[1]': &[i32; _]
     [94; 97) '[1]': [i32; _]
     [95; 96) '1': i32
     [107; 108) '2': i32
+    [107; 108) '2': i32
     [112; 115) 'foo': fn foo<i32>(&[i32]) -> &[i32]
     [112; 121) 'foo(&[2])': &[i32]
     [116; 120) '&[2]': &[i32; _]
@@ -357,9 +361,11 @@ fn test() {
     [45; 142) 'match ...     }': *const i32
     [51; 52) '1': i32
     [63; 64) '1': i32
+    [63; 64) '1': i32
     [68; 69) 't': &mut i32
     [68; 81) 't as *mut i32': *mut i32
     [91; 92) '2': i32
+    [91; 92) '2': i32
     [96; 97) 't': &mut i32
     [96; 105) 't as &i32': &i32
     [115; 116) '_': i32
diff --git a/crates/ra_hir_ty/src/tests/patterns.rs b/crates/ra_hir_ty/src/tests/patterns.rs
index 76aa32024..6e5d2247c 100644
--- a/crates/ra_hir_ty/src/tests/patterns.rs
+++ b/crates/ra_hir_ty/src/tests/patterns.rs
@@ -82,6 +82,90 @@ fn test(x: &i32) {
 }
 
 #[test]
+fn infer_literal_pattern() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn any<T>() -> T { loop {} }
+fn test(x: &i32) {
+    if let "foo" = any() {}
+    if let 1 = any() {}
+    if let 1u32 = any() {}
+    if let 1f32 = any() {}
+    if let 1.0 = any() {}
+    if let true = any() {}
+}
+"#, true),
+        @r###"
+    [18; 29) '{ loop {} }': T
+    [20; 27) 'loop {}': !
+    [25; 27) '{}': ()
+    [38; 39) 'x': &i32
+    [47; 209) '{     ...) {} }': ()
+    [53; 76) 'if let...y() {}': ()
+    [60; 65) '"foo"': &str
+    [60; 65) '"foo"': &str
+    [68; 71) 'any': fn any<&str>() -> &str
+    [68; 73) 'any()': &str
+    [74; 76) '{}': ()
+    [81; 100) 'if let...y() {}': ()
+    [88; 89) '1': i32
+    [88; 89) '1': i32
+    [92; 95) 'any': fn any<i32>() -> i32
+    [92; 97) 'any()': i32
+    [98; 100) '{}': ()
+    [105; 127) 'if let...y() {}': ()
+    [112; 116) '1u32': u32
+    [112; 116) '1u32': u32
+    [119; 122) 'any': fn any<u32>() -> u32
+    [119; 124) 'any()': u32
+    [125; 127) '{}': ()
+    [132; 154) 'if let...y() {}': ()
+    [139; 143) '1f32': f32
+    [139; 143) '1f32': f32
+    [146; 149) 'any': fn any<f32>() -> f32
+    [146; 151) 'any()': f32
+    [152; 154) '{}': ()
+    [159; 180) 'if let...y() {}': ()
+    [166; 169) '1.0': f64
+    [166; 169) '1.0': f64
+    [172; 175) 'any': fn any<f64>() -> f64
+    [172; 177) 'any()': f64
+    [178; 180) '{}': ()
+    [185; 207) 'if let...y() {}': ()
+    [192; 196) 'true': bool
+    [192; 196) 'true': bool
+    [199; 202) 'any': fn any<bool>() -> bool
+    [199; 204) 'any()': bool
+    [205; 207) '{}': ()
+    "###
+    );
+}
+
+#[test]
+fn infer_range_pattern() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn test(x: &i32) {
+    if let 1..76 = 2u32 {}
+    if let 1..=76 = 2u32 {}
+}
+"#, true),
+        @r###"
+    [9; 10) 'x': &i32
+    [18; 76) '{     ...2 {} }': ()
+    [24; 46) 'if let...u32 {}': ()
+    [31; 36) '1..76': u32
+    [39; 43) '2u32': u32
+    [44; 46) '{}': ()
+    [51; 74) 'if let...u32 {}': ()
+    [58; 64) '1..=76': u32
+    [67; 71) '2u32': u32
+    [72; 74) '{}': ()
+    "###
+    );
+}
+
+#[test]
 fn infer_pattern_match_ergonomics() {
     assert_snapshot!(
         infer(r#"
@@ -212,6 +296,7 @@ fn test() {
     [59; 62) 'arr': [f64; _]
     [73; 81) '[1.0, a]': [f64; _]
     [74; 77) '1.0': f64
+    [74; 77) '1.0': f64
     [79; 80) 'a': f64
     [85; 111) '{     ...     }': ()
     [99; 100) 'a': f64
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index a02e3ee05..2ee9b8f10 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -206,7 +206,8 @@ pub fn compute() {
     [24; 106) 'match ...     }': ()
     [30; 37) 'nope!()': {unknown}
     [48; 94) 'SizeSk...tail }': {unknown}
-    [82; 86) 'true': {unknown}
+    [82; 86) 'true': bool
+    [82; 86) 'true': bool
     [88; 92) 'tail': {unknown}
     [98; 100) '{}': ()
     "###
diff --git a/crates/ra_hir_ty/src/tests/simple.rs b/crates/ra_hir_ty/src/tests/simple.rs
index c140bd513..a600b947d 100644
--- a/crates/ra_hir_ty/src/tests/simple.rs
+++ b/crates/ra_hir_ty/src/tests/simple.rs
@@ -948,6 +948,7 @@ fn foo() {
     [165; 247) 'match ...     }': i32
     [171; 175) 'true': bool
     [186; 190) 'true': bool
+    [186; 190) 'true': bool
     [194; 195) '3': i32
     [205; 206) '_': bool
     [210; 241) '{     ...     }': !
@@ -956,6 +957,7 @@ fn foo() {
     [263; 320) 'match ...     }': i32
     [269; 273) 'true': bool
     [284; 288) 'true': bool
+    [284; 288) 'true': bool
     [292; 293) '4': i32
     [303; 304) '_': bool
     [308; 314) 'return': !
diff --git a/crates/ra_ide/src/completion.rs b/crates/ra_ide/src/completion.rs
index cd0757be5..93157bbba 100644
--- a/crates/ra_ide/src/completion.rs
+++ b/crates/ra_ide/src/completion.rs
@@ -5,8 +5,7 @@ mod completion_context;
 mod presentation;
 
 mod complete_dot;
-mod complete_record_literal;
-mod complete_record_pattern;
+mod complete_record;
 mod complete_pattern;
 mod complete_fn_param;
 mod complete_keyword;
@@ -34,15 +33,15 @@ pub use crate::completion::completion_item::{
 };
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub struct CompletionOptions {
+pub struct CompletionConfig {
     pub enable_postfix_completions: bool,
     pub add_call_parenthesis: bool,
     pub add_call_argument_snippets: bool,
 }
 
-impl Default for CompletionOptions {
+impl Default for CompletionConfig {
     fn default() -> Self {
-        CompletionOptions {
+        CompletionConfig {
             enable_postfix_completions: true,
             add_call_parenthesis: true,
             add_call_argument_snippets: true,
@@ -75,9 +74,9 @@ impl Default for CompletionOptions {
 pub(crate) fn completions(
     db: &RootDatabase,
     position: FilePosition,
-    options: &CompletionOptions,
+    config: &CompletionConfig,
 ) -> Option<Completions> {
-    let ctx = CompletionContext::new(db, position, options)?;
+    let ctx = CompletionContext::new(db, position, config)?;
 
     let mut acc = Completions::default();
 
@@ -89,8 +88,7 @@ pub(crate) fn completions(
     complete_path::complete_path(&mut acc, &ctx);
     complete_scope::complete_scope(&mut acc, &ctx);
     complete_dot::complete_dot(&mut acc, &ctx);
-    complete_record_literal::complete_record_literal(&mut acc, &ctx);
-    complete_record_pattern::complete_record_pattern(&mut acc, &ctx);
+    complete_record::complete_record(&mut acc, &ctx);
     complete_pattern::complete_pattern(&mut acc, &ctx);
     complete_postfix::complete_postfix(&mut acc, &ctx);
     complete_macro_in_item_position::complete_macro_in_item_position(&mut acc, &ctx);
diff --git a/crates/ra_ide/src/completion/complete_postfix.rs b/crates/ra_ide/src/completion/complete_postfix.rs
index 0a00054b2..29c2881c6 100644
--- a/crates/ra_ide/src/completion/complete_postfix.rs
+++ b/crates/ra_ide/src/completion/complete_postfix.rs
@@ -15,7 +15,7 @@ use crate::{
 };
 
 pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
-    if !ctx.options.enable_postfix_completions {
+    if !ctx.config.enable_postfix_completions {
         return;
     }
 
diff --git a/crates/ra_ide/src/completion/complete_record.rs b/crates/ra_ide/src/completion/complete_record.rs
new file mode 100644
index 000000000..01dd8c6db
--- /dev/null
+++ b/crates/ra_ide/src/completion/complete_record.rs
@@ -0,0 +1,411 @@
+//! Complete fields in record literals and patterns.
+use crate::completion::{CompletionContext, Completions};
+use ra_syntax::{ast, ast::NameOwner, SmolStr};
+
+pub(super) fn complete_record(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
+    let (ty, variant, already_present_fields) =
+        match (ctx.record_lit_pat.as_ref(), ctx.record_lit_syntax.as_ref()) {
+            (None, None) => return None,
+            (Some(_), Some(_)) => panic!("A record cannot be both a literal and a pattern"),
+            (Some(record_pat), _) => (
+                ctx.sema.type_of_pat(&record_pat.clone().into())?,
+                ctx.sema.resolve_record_pattern(record_pat)?,
+                pattern_ascribed_fields(record_pat),
+            ),
+            (_, Some(record_lit)) => (
+                ctx.sema.type_of_expr(&record_lit.clone().into())?,
+                ctx.sema.resolve_record_literal(record_lit)?,
+                literal_ascribed_fields(record_lit),
+            ),
+        };
+
+    for (field, field_ty) in ty.variant_fields(ctx.db, variant).into_iter().filter(|(field, _)| {
+        // FIXME: already_present_names better be `Vec<hir::Name>`
+        !already_present_fields.contains(&SmolStr::from(field.name(ctx.db).to_string()))
+    }) {
+        acc.add_field(ctx, field, &field_ty);
+    }
+    Some(())
+}
+
+fn literal_ascribed_fields(record_lit: &ast::RecordLit) -> Vec<SmolStr> {
+    record_lit
+        .record_field_list()
+        .map(|field_list| field_list.fields())
+        .map(|fields| {
+            fields
+                .into_iter()
+                .filter_map(|field| field.name_ref())
+                .map(|name_ref| name_ref.text().clone())
+                .collect()
+        })
+        .unwrap_or_default()
+}
+
+fn pattern_ascribed_fields(record_pat: &ast::RecordPat) -> Vec<SmolStr> {
+    record_pat
+        .record_field_pat_list()
+        .map(|pat_list| {
+            pat_list
+                .record_field_pats()
+                .filter_map(|fild_pat| fild_pat.name())
+                .chain(pat_list.bind_pats().filter_map(|bind_pat| bind_pat.name()))
+                .map(|name| name.text().clone())
+                .collect()
+        })
+        .unwrap_or_default()
+}
+
+#[cfg(test)]
+mod tests {
+    mod record_lit_tests {
+        use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
+        use insta::assert_debug_snapshot;
+
+        fn complete(code: &str) -> Vec<CompletionItem> {
+            do_completion(code, CompletionKind::Reference)
+        }
+
+        #[test]
+        fn test_record_pattern_field() {
+            let completions = complete(
+                r"
+            struct S { foo: u32 }
+
+            fn process(f: S) {
+                match f {
+                    S { f<|>: 92 } => (),
+                }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "foo",
+                source_range: [117; 118),
+                delete: [117; 118),
+                insert: "foo",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_pattern_enum_variant() {
+            let completions = complete(
+                r"
+            enum E {
+                S { foo: u32, bar: () }
+            }
+
+            fn process(e: E) {
+                match e {
+                    E::S { <|> } => (),
+                }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "bar",
+                source_range: [161; 161),
+                delete: [161; 161),
+                insert: "bar",
+                kind: Field,
+                detail: "()",
+            },
+            CompletionItem {
+                label: "foo",
+                source_range: [161; 161),
+                delete: [161; 161),
+                insert: "foo",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_pattern_field_in_simple_macro() {
+            let completions = complete(
+                r"
+            macro_rules! m { ($e:expr) => { $e } }
+            struct S { foo: u32 }
+
+            fn process(f: S) {
+                m!(match f {
+                    S { f<|>: 92 } => (),
+                })
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "foo",
+                source_range: [171; 172),
+                delete: [171; 172),
+                insert: "foo",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn only_missing_fields_are_completed_in_destruct_pats() {
+            let completions = complete(
+                r"
+            struct S {
+                foo1: u32,
+                foo2: u32,
+                bar: u32,
+                baz: u32,
+            }
+
+            fn main() {
+                let s = S {
+                    foo1: 1,
+                    foo2: 2,
+                    bar: 3,
+                    baz: 4,
+                };
+                if let S { foo1, foo2: a, <|> } = s {}
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "bar",
+                source_range: [372; 372),
+                delete: [372; 372),
+                insert: "bar",
+                kind: Field,
+                detail: "u32",
+            },
+            CompletionItem {
+                label: "baz",
+                source_range: [372; 372),
+                delete: [372; 372),
+                insert: "baz",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+    }
+
+    mod record_pat_tests {
+        use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
+        use insta::assert_debug_snapshot;
+
+        fn complete(code: &str) -> Vec<CompletionItem> {
+            do_completion(code, CompletionKind::Reference)
+        }
+
+        #[test]
+        fn test_record_literal_deprecated_field() {
+            let completions = complete(
+                r"
+            struct A {
+                #[deprecated]
+                the_field: u32,
+            }
+            fn foo() {
+               A { the<|> }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "the_field",
+                source_range: [142; 145),
+                delete: [142; 145),
+                insert: "the_field",
+                kind: Field,
+                detail: "u32",
+                deprecated: true,
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_literal_field() {
+            let completions = complete(
+                r"
+            struct A { the_field: u32 }
+            fn foo() {
+               A { the<|> }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "the_field",
+                source_range: [83; 86),
+                delete: [83; 86),
+                insert: "the_field",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_literal_enum_variant() {
+            let completions = complete(
+                r"
+            enum E {
+                A { a: u32 }
+            }
+            fn foo() {
+                let _ = E::A { <|> }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "a",
+                source_range: [119; 119),
+                delete: [119; 119),
+                insert: "a",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_literal_two_structs() {
+            let completions = complete(
+                r"
+            struct A { a: u32 }
+            struct B { b: u32 }
+
+            fn foo() {
+               let _: A = B { <|> }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "b",
+                source_range: [119; 119),
+                delete: [119; 119),
+                insert: "b",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_literal_generic_struct() {
+            let completions = complete(
+                r"
+            struct A<T> { a: T }
+
+            fn foo() {
+               let _: A<u32> = A { <|> }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "a",
+                source_range: [93; 93),
+                delete: [93; 93),
+                insert: "a",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn test_record_literal_field_in_simple_macro() {
+            let completions = complete(
+                r"
+            macro_rules! m { ($e:expr) => { $e } }
+            struct A { the_field: u32 }
+            fn foo() {
+               m!(A { the<|> })
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "the_field",
+                source_range: [137; 140),
+                delete: [137; 140),
+                insert: "the_field",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+
+        #[test]
+        fn only_missing_fields_are_completed() {
+            let completions = complete(
+                r"
+            struct S {
+                foo1: u32,
+                foo2: u32,
+                bar: u32,
+                baz: u32,
+            }
+
+            fn main() {
+                let foo1 = 1;
+                let s = S {
+                    foo1,
+                    foo2: 5,
+                    <|>
+                }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "bar",
+                source_range: [302; 302),
+                delete: [302; 302),
+                insert: "bar",
+                kind: Field,
+                detail: "u32",
+            },
+            CompletionItem {
+                label: "baz",
+                source_range: [302; 302),
+                delete: [302; 302),
+                insert: "baz",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
+    }
+}
diff --git a/crates/ra_ide/src/completion/complete_record_literal.rs b/crates/ra_ide/src/completion/complete_record_literal.rs
deleted file mode 100644
index e4e764f58..000000000
--- a/crates/ra_ide/src/completion/complete_record_literal.rs
+++ /dev/null
@@ -1,241 +0,0 @@
-//! FIXME: write short doc here
-
-use crate::completion::{CompletionContext, Completions};
-use ra_syntax::SmolStr;
-
-/// Complete fields in fields literals.
-pub(super) fn complete_record_literal(acc: &mut Completions, ctx: &CompletionContext) {
-    let (ty, variant) = match ctx.record_lit_syntax.as_ref().and_then(|it| {
-        Some((ctx.sema.type_of_expr(&it.clone().into())?, ctx.sema.resolve_record_literal(it)?))
-    }) {
-        Some(it) => it,
-        _ => return,
-    };
-
-    let already_present_names: Vec<SmolStr> = ctx
-        .record_lit_syntax
-        .as_ref()
-        .and_then(|record_literal| record_literal.record_field_list())
-        .map(|field_list| field_list.fields())
-        .map(|fields| {
-            fields
-                .into_iter()
-                .filter_map(|field| field.name_ref())
-                .map(|name_ref| name_ref.text().clone())
-                .collect()
-        })
-        .unwrap_or_default();
-
-    for (field, field_ty) in ty.variant_fields(ctx.db, variant) {
-        if !already_present_names.contains(&SmolStr::from(field.name(ctx.db).to_string())) {
-            acc.add_field(ctx, field, &field_ty);
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
-    use insta::assert_debug_snapshot;
-
-    fn complete(code: &str) -> Vec<CompletionItem> {
-        do_completion(code, CompletionKind::Reference)
-    }
-
-    #[test]
-    fn test_record_literal_deprecated_field() {
-        let completions = complete(
-            r"
-            struct A {
-                #[deprecated]
-                the_field: u32,
-            }
-            fn foo() {
-               A { the<|> }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "the_field",
-                source_range: [142; 145),
-                delete: [142; 145),
-                insert: "the_field",
-                kind: Field,
-                detail: "u32",
-                deprecated: true,
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_literal_field() {
-        let completions = complete(
-            r"
-            struct A { the_field: u32 }
-            fn foo() {
-               A { the<|> }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "the_field",
-                source_range: [83; 86),
-                delete: [83; 86),
-                insert: "the_field",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_literal_enum_variant() {
-        let completions = complete(
-            r"
-            enum E {
-                A { a: u32 }
-            }
-            fn foo() {
-                let _ = E::A { <|> }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "a",
-                source_range: [119; 119),
-                delete: [119; 119),
-                insert: "a",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_literal_two_structs() {
-        let completions = complete(
-            r"
-            struct A { a: u32 }
-            struct B { b: u32 }
-
-            fn foo() {
-               let _: A = B { <|> }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "b",
-                source_range: [119; 119),
-                delete: [119; 119),
-                insert: "b",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_literal_generic_struct() {
-        let completions = complete(
-            r"
-            struct A<T> { a: T }
-
-            fn foo() {
-               let _: A<u32> = A { <|> }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "a",
-                source_range: [93; 93),
-                delete: [93; 93),
-                insert: "a",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_literal_field_in_simple_macro() {
-        let completions = complete(
-            r"
-            macro_rules! m { ($e:expr) => { $e } }
-            struct A { the_field: u32 }
-            fn foo() {
-               m!(A { the<|> })
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "the_field",
-                source_range: [137; 140),
-                delete: [137; 140),
-                insert: "the_field",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn only_missing_fields_are_completed() {
-        let completions = complete(
-            r"
-            struct S {
-                foo1: u32,
-                foo2: u32,
-                bar: u32,
-                baz: u32,
-            }
-
-            fn main() {
-                let foo1 = 1;
-                let s = S {
-                    foo1,
-                    foo2: 5,
-                    <|>
-                }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "bar",
-                source_range: [302; 302),
-                delete: [302; 302),
-                insert: "bar",
-                kind: Field,
-                detail: "u32",
-            },
-            CompletionItem {
-                label: "baz",
-                source_range: [302; 302),
-                delete: [302; 302),
-                insert: "baz",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-}
diff --git a/crates/ra_ide/src/completion/complete_record_pattern.rs b/crates/ra_ide/src/completion/complete_record_pattern.rs
deleted file mode 100644
index 962376428..000000000
--- a/crates/ra_ide/src/completion/complete_record_pattern.rs
+++ /dev/null
@@ -1,118 +0,0 @@
-//! FIXME: write short doc here
-
-use crate::completion::{CompletionContext, Completions};
-
-pub(super) fn complete_record_pattern(acc: &mut Completions, ctx: &CompletionContext) {
-    let (ty, variant) = match ctx.record_lit_pat.as_ref().and_then(|it| {
-        Some((ctx.sema.type_of_pat(&it.clone().into())?, ctx.sema.resolve_record_pattern(it)?))
-    }) {
-        Some(it) => it,
-        _ => return,
-    };
-
-    for (field, field_ty) in ty.variant_fields(ctx.db, variant) {
-        acc.add_field(ctx, field, &field_ty);
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
-    use insta::assert_debug_snapshot;
-
-    fn complete(code: &str) -> Vec<CompletionItem> {
-        do_completion(code, CompletionKind::Reference)
-    }
-
-    #[test]
-    fn test_record_pattern_field() {
-        let completions = complete(
-            r"
-            struct S { foo: u32 }
-
-            fn process(f: S) {
-                match f {
-                    S { f<|>: 92 } => (),
-                }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "foo",
-                source_range: [117; 118),
-                delete: [117; 118),
-                insert: "foo",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_pattern_enum_variant() {
-        let completions = complete(
-            r"
-            enum E {
-                S { foo: u32, bar: () }
-            }
-
-            fn process(e: E) {
-                match e {
-                    E::S { <|> } => (),
-                }
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "bar",
-                source_range: [161; 161),
-                delete: [161; 161),
-                insert: "bar",
-                kind: Field,
-                detail: "()",
-            },
-            CompletionItem {
-                label: "foo",
-                source_range: [161; 161),
-                delete: [161; 161),
-                insert: "foo",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-
-    #[test]
-    fn test_record_pattern_field_in_simple_macro() {
-        let completions = complete(
-            r"
-            macro_rules! m { ($e:expr) => { $e } }
-            struct S { foo: u32 }
-
-            fn process(f: S) {
-                m!(match f {
-                    S { f<|>: 92 } => (),
-                })
-            }
-            ",
-        );
-        assert_debug_snapshot!(completions, @r###"
-        [
-            CompletionItem {
-                label: "foo",
-                source_range: [171; 172),
-                delete: [171; 172),
-                insert: "foo",
-                kind: Field,
-                detail: "u32",
-            },
-        ]
-        "###);
-    }
-}
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index 319e33b61..fdc0da2c5 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -11,7 +11,7 @@ use ra_syntax::{
 };
 use ra_text_edit::AtomTextEdit;
 
-use crate::{completion::CompletionOptions, FilePosition};
+use crate::{completion::CompletionConfig, FilePosition};
 
 /// `CompletionContext` is created early during completion to figure out, where
 /// exactly is the cursor, syntax-wise.
@@ -19,7 +19,7 @@ use crate::{completion::CompletionOptions, FilePosition};
 pub(crate) struct CompletionContext<'a> {
     pub(super) sema: Semantics<'a, RootDatabase>,
     pub(super) db: &'a RootDatabase,
-    pub(super) options: &'a CompletionOptions,
+    pub(super) config: &'a CompletionConfig,
     pub(super) offset: TextUnit,
     /// The token before the cursor, in the original file.
     pub(super) original_token: SyntaxToken,
@@ -61,7 +61,7 @@ impl<'a> CompletionContext<'a> {
     pub(super) fn new(
         db: &'a RootDatabase,
         position: FilePosition,
-        options: &'a CompletionOptions,
+        config: &'a CompletionConfig,
     ) -> Option<CompletionContext<'a>> {
         let sema = Semantics::new(db);
 
@@ -85,7 +85,7 @@ impl<'a> CompletionContext<'a> {
         let mut ctx = CompletionContext {
             sema,
             db,
-            options,
+            config,
             original_token,
             token,
             offset: position.offset,
diff --git a/crates/ra_ide/src/completion/presentation.rs b/crates/ra_ide/src/completion/presentation.rs
index 60f1b83f3..1c7c0924d 100644
--- a/crates/ra_ide/src/completion/presentation.rs
+++ b/crates/ra_ide/src/completion/presentation.rs
@@ -106,7 +106,7 @@ impl Completions {
         };
 
         // Add `<>` for generic types
-        if ctx.is_path_type && !ctx.has_type_args && ctx.options.add_call_parenthesis {
+        if ctx.is_path_type && !ctx.has_type_args && ctx.config.add_call_parenthesis {
             let has_non_default_type_params = match resolution {
                 ScopeDef::ModuleDef(Adt(it)) => it.has_non_default_type_params(ctx.db),
                 ScopeDef::ModuleDef(TypeAlias(it)) => it.has_non_default_type_params(ctx.db),
@@ -211,14 +211,14 @@ impl Completions {
                 .detail(function_signature.to_string());
 
         // If not an import, add parenthesis automatically.
-        if ctx.use_item_syntax.is_none() && !ctx.is_call && ctx.options.add_call_parenthesis {
+        if ctx.use_item_syntax.is_none() && !ctx.is_call && ctx.config.add_call_parenthesis {
             tested_by!(inserts_parens_for_function_calls);
 
             let (snippet, label) = if params.is_empty() || has_self_param && params.len() == 1 {
                 (format!("{}()$0", name), format!("{}()", name))
             } else {
                 builder = builder.trigger_call_info();
-                let snippet = if ctx.options.add_call_argument_snippets {
+                let snippet = if ctx.config.add_call_argument_snippets {
                     let to_skip = if has_self_param { 1 } else { 0 };
                     let function_params_snippet = function_signature
                         .parameter_names
@@ -311,7 +311,7 @@ mod tests {
 
     use crate::completion::{
         test_utils::{do_completion, do_completion_with_options},
-        CompletionItem, CompletionKind, CompletionOptions,
+        CompletionConfig, CompletionItem, CompletionKind,
     };
 
     fn do_reference_completion(ra_fixture: &str) -> Vec<CompletionItem> {
@@ -320,7 +320,7 @@ mod tests {
 
     fn do_reference_completion_with_options(
         ra_fixture: &str,
-        options: CompletionOptions,
+        options: CompletionConfig,
     ) -> Vec<CompletionItem> {
         do_completion_with_options(ra_fixture, CompletionKind::Reference, &options)
     }
@@ -589,7 +589,7 @@ mod tests {
                     s.f<|>
                 }
                 ",
-                CompletionOptions {
+                CompletionConfig {
                     add_call_argument_snippets: false,
                     .. Default::default()
                 }
diff --git a/crates/ra_ide/src/completion/test_utils.rs b/crates/ra_ide/src/completion/test_utils.rs
index 136857315..eb90b5279 100644
--- a/crates/ra_ide/src/completion/test_utils.rs
+++ b/crates/ra_ide/src/completion/test_utils.rs
@@ -1,19 +1,19 @@
 //! Runs completion for testing purposes.
 
 use crate::{
-    completion::{completion_item::CompletionKind, CompletionOptions},
+    completion::{completion_item::CompletionKind, CompletionConfig},
     mock_analysis::{analysis_and_position, single_file_with_position},
     CompletionItem,
 };
 
 pub(crate) fn do_completion(code: &str, kind: CompletionKind) -> Vec<CompletionItem> {
-    do_completion_with_options(code, kind, &CompletionOptions::default())
+    do_completion_with_options(code, kind, &CompletionConfig::default())
 }
 
 pub(crate) fn do_completion_with_options(
     code: &str,
     kind: CompletionKind,
-    options: &CompletionOptions,
+    options: &CompletionConfig,
 ) -> Vec<CompletionItem> {
     let (analysis, position) = if code.contains("//-") {
         analysis_and_position(code)
diff --git a/crates/ra_ide/src/inlay_hints.rs b/crates/ra_ide/src/inlay_hints.rs
index f4f0751c0..4b133b19b 100644
--- a/crates/ra_ide/src/inlay_hints.rs
+++ b/crates/ra_ide/src/inlay_hints.rs
@@ -11,14 +11,14 @@ use ra_syntax::{
 use crate::{FileId, FunctionSignature};
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub struct InlayHintsOptions {
+pub struct InlayHintsConfig {
     pub type_hints: bool,
     pub parameter_hints: bool,
     pub chaining_hints: bool,
     pub max_length: Option<usize>,
 }
 
-impl Default for InlayHintsOptions {
+impl Default for InlayHintsConfig {
     fn default() -> Self {
         Self { type_hints: true, parameter_hints: true, chaining_hints: true, max_length: None }
     }
@@ -41,7 +41,7 @@ pub struct InlayHint {
 pub(crate) fn inlay_hints(
     db: &RootDatabase,
     file_id: FileId,
-    options: &InlayHintsOptions,
+    config: &InlayHintsConfig,
 ) -> Vec<InlayHint> {
     let _p = profile("inlay_hints");
     let sema = Semantics::new(db);
@@ -50,14 +50,14 @@ pub(crate) fn inlay_hints(
     let mut res = Vec::new();
     for node in file.syntax().descendants() {
         if let Some(expr) = ast::Expr::cast(node.clone()) {
-            get_chaining_hints(&mut res, &sema, options, expr);
+            get_chaining_hints(&mut res, &sema, config, expr);
         }
 
         match_ast! {
             match node {
-                ast::CallExpr(it) => { get_param_name_hints(&mut res, &sema, options, ast::Expr::from(it)); },
-                ast::MethodCallExpr(it) => { get_param_name_hints(&mut res, &sema, options, ast::Expr::from(it)); },
-                ast::BindPat(it) => { get_bind_pat_hints(&mut res, &sema, options, it); },
+                ast::CallExpr(it) => { get_param_name_hints(&mut res, &sema, config, ast::Expr::from(it)); },
+                ast::MethodCallExpr(it) => { get_param_name_hints(&mut res, &sema, config, ast::Expr::from(it)); },
+                ast::BindPat(it) => { get_bind_pat_hints(&mut res, &sema, config, it); },
                 _ => (),
             }
         }
@@ -68,15 +68,14 @@ pub(crate) fn inlay_hints(
 fn get_chaining_hints(
     acc: &mut Vec<InlayHint>,
     sema: &Semantics<RootDatabase>,
-    options: &InlayHintsOptions,
+    config: &InlayHintsConfig,
     expr: ast::Expr,
 ) -> Option<()> {
-    if !options.chaining_hints {
+    if !config.chaining_hints {
         return None;
     }
 
-    let ty = sema.type_of_expr(&expr)?;
-    if ty.is_unknown() {
+    if matches!(expr, ast::Expr::RecordLit(_)) {
         return None;
     }
 
@@ -95,7 +94,18 @@ fn get_chaining_hints(
     let next = tokens.next()?.kind();
     let next_next = tokens.next()?.kind();
     if next == SyntaxKind::WHITESPACE && next_next == SyntaxKind::DOT {
-        let label = ty.display_truncated(sema.db, options.max_length).to_string();
+        let ty = sema.type_of_expr(&expr)?;
+        if ty.is_unknown() {
+            return None;
+        }
+        if matches!(expr, ast::Expr::PathExpr(_)) {
+            if let Some(Adt::Struct(st)) = ty.as_adt() {
+                if st.fields(sema.db).is_empty() {
+                    return None;
+                }
+            }
+        }
+        let label = ty.display_truncated(sema.db, config.max_length).to_string();
         acc.push(InlayHint {
             range: expr.syntax().text_range(),
             kind: InlayKind::ChainingHint,
@@ -108,10 +118,10 @@ fn get_chaining_hints(
 fn get_param_name_hints(
     acc: &mut Vec<InlayHint>,
     sema: &Semantics<RootDatabase>,
-    options: &InlayHintsOptions,
+    config: &InlayHintsConfig,
     expr: ast::Expr,
 ) -> Option<()> {
-    if !options.parameter_hints {
+    if !config.parameter_hints {
         return None;
     }
 
@@ -148,10 +158,10 @@ fn get_param_name_hints(
 fn get_bind_pat_hints(
     acc: &mut Vec<InlayHint>,
     sema: &Semantics<RootDatabase>,
-    options: &InlayHintsOptions,
+    config: &InlayHintsConfig,
     pat: ast::BindPat,
 ) -> Option<()> {
-    if !options.type_hints {
+    if !config.type_hints {
         return None;
     }
 
@@ -164,7 +174,7 @@ fn get_bind_pat_hints(
     acc.push(InlayHint {
         range: pat.syntax().text_range(),
         kind: InlayKind::TypeHint,
-        label: ty.display_truncated(sema.db, options.max_length).to_string().into(),
+        label: ty.display_truncated(sema.db, config.max_length).to_string().into(),
     });
     Some(())
 }
@@ -270,7 +280,7 @@ fn get_fn_signature(sema: &Semantics<RootDatabase>, expr: &ast::Expr) -> Option<
 
 #[cfg(test)]
 mod tests {
-    use crate::inlay_hints::InlayHintsOptions;
+    use crate::inlay_hints::InlayHintsConfig;
     use insta::assert_debug_snapshot;
 
     use crate::mock_analysis::single_file;
@@ -284,7 +294,7 @@ mod tests {
                 let _x = foo(4, 4);
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ parameter_hints: true, type_hints: false, chaining_hints: false, max_length: None}).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ parameter_hints: true, type_hints: false, chaining_hints: false, max_length: None}).unwrap(), @r###"
         [
             InlayHint {
                 range: [106; 107),
@@ -308,7 +318,7 @@ mod tests {
                 let _x = foo(4, 4);
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ type_hints: false, parameter_hints: false, chaining_hints: false, max_length: None}).unwrap(), @r###"[]"###);
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ type_hints: false, parameter_hints: false, chaining_hints: false, max_length: None}).unwrap(), @r###"[]"###);
     }
 
     #[test]
@@ -320,7 +330,7 @@ mod tests {
                 let _x = foo(4, 4);
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ type_hints: true, parameter_hints: false, chaining_hints: false, max_length: None}).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ type_hints: true, parameter_hints: false, chaining_hints: false, max_length: None}).unwrap(), @r###"
         [
             InlayHint {
                 range: [97; 99),
@@ -344,7 +354,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [69; 71),
@@ -401,7 +411,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [193; 197),
@@ -481,7 +491,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [21; 30),
@@ -545,7 +555,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [21; 30),
@@ -595,7 +605,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [188; 192),
@@ -690,7 +700,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [188; 192),
@@ -785,7 +795,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [252; 256),
@@ -857,7 +867,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions { max_length: Some(8), ..Default::default() }).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig { max_length: Some(8), ..Default::default() }).unwrap(), @r###"
         [
             InlayHint {
                 range: [74; 75),
@@ -945,7 +955,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions::default()).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig::default()).unwrap(), @r###"
         [
             InlayHint {
                 range: [798; 809),
@@ -1067,7 +1077,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions { max_length: Some(8), ..Default::default() }).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig { max_length: Some(8), ..Default::default() }).unwrap(), @r###"
         []
         "###
         );
@@ -1093,7 +1103,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions { max_length: Some(8), ..Default::default() }).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig { max_length: Some(8), ..Default::default() }).unwrap(), @r###"
         []
         "###
         );
@@ -1115,7 +1125,7 @@ fn main() {
                     .into_c();
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"
         [
             InlayHint {
                 range: [232; 269),
@@ -1144,7 +1154,7 @@ fn main() {
                 let c = A(B(C)).into_b().into_c();
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"[]"###);
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"[]"###);
     }
 
     #[test]
@@ -1154,32 +1164,35 @@ fn main() {
             struct A { pub b: B }
             struct B { pub c: C }
             struct C(pub bool);
+            struct D;
+
+            impl D {
+                fn foo(&self) -> i32 { 42 }
+            }
 
             fn main() {
                 let x = A { b: B { c: C(true) } }
                     .b
                     .c
                     .0;
+                let x = D
+                    .foo();
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"
         [
             InlayHint {
-                range: [150; 221),
+                range: [252; 323),
                 kind: ChainingHint,
                 label: "C",
             },
             InlayHint {
-                range: [150; 198),
+                range: [252; 300),
                 kind: ChainingHint,
                 label: "B",
             },
-            InlayHint {
-                range: [150; 175),
-                kind: ChainingHint,
-                label: "A",
-            },
-        ]"###);
+        ]
+        "###);
     }
 
     #[test]
@@ -1204,7 +1217,7 @@ fn main() {
                     .into_c();
             }"#,
         );
-        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsOptions{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, &InlayHintsConfig{ parameter_hints: false, type_hints: false, chaining_hints: true, max_length: None}).unwrap(), @r###"
         [
             InlayHint {
                 range: [403; 452),
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index e43414985..285381086 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -62,13 +62,13 @@ use crate::display::ToNav;
 pub use crate::{
     assists::{Assist, AssistId},
     call_hierarchy::CallItem,
-    completion::{CompletionItem, CompletionItemKind, CompletionOptions, InsertTextFormat},
+    completion::{CompletionConfig, CompletionItem, CompletionItemKind, InsertTextFormat},
     diagnostics::Severity,
     display::{file_structure, FunctionSignature, NavigationTarget, StructureNode},
     expand_macro::ExpandedMacro,
     folding_ranges::{Fold, FoldKind},
     hover::HoverResult,
-    inlay_hints::{InlayHint, InlayHintsOptions, InlayKind},
+    inlay_hints::{InlayHint, InlayHintsConfig, InlayKind},
     references::{Declaration, Reference, ReferenceAccess, ReferenceKind, ReferenceSearchResult},
     runnables::{Runnable, RunnableKind, TestId},
     source_change::{FileSystemEdit, SourceChange, SourceFileEdit},
@@ -138,6 +138,11 @@ impl AnalysisHost {
     pub fn new(lru_capacity: Option<usize>) -> AnalysisHost {
         AnalysisHost { db: RootDatabase::new(lru_capacity) }
     }
+
+    pub fn update_lru_capacity(&mut self, lru_capacity: Option<usize>) {
+        self.db.update_lru_capacity(lru_capacity);
+    }
+
     /// Returns a snapshot of the current state, which you can query for
     /// semantic information.
     pub fn analysis(&self) -> Analysis {
@@ -320,9 +325,9 @@ impl Analysis {
     pub fn inlay_hints(
         &self,
         file_id: FileId,
-        inlay_hint_opts: &InlayHintsOptions,
+        config: &InlayHintsConfig,
     ) -> Cancelable<Vec<InlayHint>> {
-        self.with_db(|db| inlay_hints::inlay_hints(db, file_id, inlay_hint_opts))
+        self.with_db(|db| inlay_hints::inlay_hints(db, file_id, config))
     }
 
     /// Returns the set of folding ranges.
@@ -445,9 +450,9 @@ impl Analysis {
     pub fn completions(
         &self,
         position: FilePosition,
-        options: &CompletionOptions,
+        config: &CompletionConfig,
     ) -> Cancelable<Option<Vec<CompletionItem>>> {
-        self.with_db(|db| completion::completions(db, position, options).map(Into::into))
+        self.with_db(|db| completion::completions(db, position, config).map(Into::into))
     }
 
     /// Computes assists (aka code actions aka intentions) for the given
diff --git a/crates/ra_ide/src/ssr.rs b/crates/ra_ide/src/ssr.rs
index 1c9710a5d..1abb891c1 100644
--- a/crates/ra_ide/src/ssr.rs
+++ b/crates/ra_ide/src/ssr.rs
@@ -5,7 +5,7 @@ use ra_db::{SourceDatabase, SourceDatabaseExt};
 use ra_ide_db::symbol_index::SymbolsDatabase;
 use ra_ide_db::RootDatabase;
 use ra_syntax::ast::make::try_expr_from_text;
-use ra_syntax::ast::{AstToken, Comment};
+use ra_syntax::ast::{AstToken, Comment, RecordField, RecordLit};
 use ra_syntax::{AstNode, SyntaxElement, SyntaxNode};
 use ra_text_edit::{TextEdit, TextEditBuilder};
 use rustc_hash::FxHashMap;
@@ -186,47 +186,102 @@ fn create_name<'a>(name: &str, vars: &'a mut Vec<Var>) -> Result<&'a str, SsrErr
 }
 
 fn find(pattern: &SsrPattern, code: &SyntaxNode) -> SsrMatches {
+    fn check_record_lit(
+        pattern: RecordLit,
+        code: RecordLit,
+        placeholders: &[Var],
+        match_: Match,
+    ) -> Option<Match> {
+        let match_ = check_opt_nodes(pattern.path(), code.path(), placeholders, match_)?;
+
+        let mut pattern_fields =
+            pattern.record_field_list().map(|x| x.fields().collect()).unwrap_or(vec![]);
+        let mut code_fields =
+            code.record_field_list().map(|x| x.fields().collect()).unwrap_or(vec![]);
+
+        if pattern_fields.len() != code_fields.len() {
+            return None;
+        }
+
+        let by_name = |a: &RecordField, b: &RecordField| {
+            a.name_ref()
+                .map(|x| x.syntax().text().to_string())
+                .cmp(&b.name_ref().map(|x| x.syntax().text().to_string()))
+        };
+        pattern_fields.sort_by(by_name);
+        code_fields.sort_by(by_name);
+
+        pattern_fields.into_iter().zip(code_fields.into_iter()).fold(
+            Some(match_),
+            |accum, (a, b)| {
+                accum.and_then(|match_| check_opt_nodes(Some(a), Some(b), placeholders, match_))
+            },
+        )
+    }
+
+    fn check_opt_nodes(
+        pattern: Option<impl AstNode>,
+        code: Option<impl AstNode>,
+        placeholders: &[Var],
+        match_: Match,
+    ) -> Option<Match> {
+        match (pattern, code) {
+            (Some(pattern), Some(code)) => check(
+                &SyntaxElement::from(pattern.syntax().clone()),
+                &SyntaxElement::from(code.syntax().clone()),
+                placeholders,
+                match_,
+            ),
+            (None, None) => Some(match_),
+            _ => None,
+        }
+    }
+
     fn check(
         pattern: &SyntaxElement,
         code: &SyntaxElement,
         placeholders: &[Var],
         mut match_: Match,
     ) -> Option<Match> {
-        match (pattern, code) {
-            (SyntaxElement::Token(ref pattern), SyntaxElement::Token(ref code)) => {
+        match (&pattern, &code) {
+            (SyntaxElement::Token(pattern), SyntaxElement::Token(code)) => {
                 if pattern.text() == code.text() {
                     Some(match_)
                 } else {
                     None
                 }
             }
-            (SyntaxElement::Node(ref pattern), SyntaxElement::Node(ref code)) => {
+            (SyntaxElement::Node(pattern), SyntaxElement::Node(code)) => {
                 if placeholders.iter().any(|n| n.0.as_str() == pattern.text()) {
                     match_.binding.insert(Var(pattern.text().to_string()), code.clone());
                     Some(match_)
                 } else {
-                    let mut pattern_children = pattern
-                        .children_with_tokens()
-                        .filter(|element| !element.kind().is_trivia());
-                    let mut code_children =
-                        code.children_with_tokens().filter(|element| !element.kind().is_trivia());
-                    let new_ignored_comments = code.children_with_tokens().filter_map(|element| {
-                        element.as_token().and_then(|token| Comment::cast(token.clone()))
-                    });
-                    match_.ignored_comments.extend(new_ignored_comments);
-                    let match_from_children = pattern_children
-                        .by_ref()
-                        .zip(code_children.by_ref())
-                        .fold(Some(match_), |accum, (a, b)| {
-                            accum.and_then(|match_| check(&a, &b, placeholders, match_))
-                        });
-                    match_from_children.and_then(|match_| {
-                        if pattern_children.count() == 0 && code_children.count() == 0 {
-                            Some(match_)
-                        } else {
-                            None
-                        }
-                    })
+                    if let (Some(pattern), Some(code)) =
+                        (RecordLit::cast(pattern.clone()), RecordLit::cast(code.clone()))
+                    {
+                        check_record_lit(pattern, code, placeholders, match_)
+                    } else {
+                        let mut pattern_children = pattern
+                            .children_with_tokens()
+                            .filter(|element| !element.kind().is_trivia());
+                        let mut code_children = code
+                            .children_with_tokens()
+                            .filter(|element| !element.kind().is_trivia());
+                        let new_ignored_comments =
+                            code.children_with_tokens().filter_map(|element| {
+                                element.as_token().and_then(|token| Comment::cast(token.clone()))
+                            });
+                        match_.ignored_comments.extend(new_ignored_comments);
+                        pattern_children
+                            .by_ref()
+                            .zip(code_children.by_ref())
+                            .fold(Some(match_), |accum, (a, b)| {
+                                accum.and_then(|match_| check(&a, &b, placeholders, match_))
+                            })
+                            .filter(|_| {
+                                pattern_children.next().is_none() && code_children.next().is_none()
+                            })
+                    }
                 }
             }
             _ => None,
@@ -434,4 +489,13 @@ mod tests {
             "fn main() { bar(5)/* using 5 */ }",
         )
     }
+
+    #[test]
+    fn ssr_struct_lit() {
+        assert_ssr_transform(
+            "foo{a: $a:expr, b: $b:expr} ==>> foo::new($a, $b)",
+            "fn main() { foo{b:2, a:1} }",
+            "fn main() { foo::new(1, 2) }",
+        )
+    }
 }
diff --git a/crates/ra_ide_db/src/lib.rs b/crates/ra_ide_db/src/lib.rs
index 4faeefa8d..e6f2d36e9 100644
--- a/crates/ra_ide_db/src/lib.rs
+++ b/crates/ra_ide_db/src/lib.rs
@@ -115,12 +115,16 @@ impl RootDatabase {
         db.set_crate_graph_with_durability(Default::default(), Durability::HIGH);
         db.set_local_roots_with_durability(Default::default(), Durability::HIGH);
         db.set_library_roots_with_durability(Default::default(), Durability::HIGH);
-        let lru_capacity = lru_capacity.unwrap_or(ra_db::DEFAULT_LRU_CAP);
-        db.query_mut(ra_db::ParseQuery).set_lru_capacity(lru_capacity);
-        db.query_mut(hir::db::ParseMacroQuery).set_lru_capacity(lru_capacity);
-        db.query_mut(hir::db::MacroExpandQuery).set_lru_capacity(lru_capacity);
+        db.update_lru_capacity(lru_capacity);
         db
     }
+
+    pub fn update_lru_capacity(&mut self, lru_capacity: Option<usize>) {
+        let lru_capacity = lru_capacity.unwrap_or(ra_db::DEFAULT_LRU_CAP);
+        self.query_mut(ra_db::ParseQuery).set_lru_capacity(lru_capacity);
+        self.query_mut(hir::db::ParseMacroQuery).set_lru_capacity(lru_capacity);
+        self.query_mut(hir::db::MacroExpandQuery).set_lru_capacity(lru_capacity);
+    }
 }
 
 impl salsa::ParallelDatabase for RootDatabase {
diff --git a/crates/ra_proc_macro/Cargo.toml b/crates/ra_proc_macro/Cargo.toml
index bc2c37296..d009ceb82 100644
--- a/crates/ra_proc_macro/Cargo.toml
+++ b/crates/ra_proc_macro/Cargo.toml
@@ -10,3 +10,8 @@ doctest = false
 
 [dependencies]
 ra_tt = { path = "../ra_tt" }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+log = "0.4.8"
+crossbeam-channel = "0.4.0"
+jod-thread = "0.1.1"
diff --git a/crates/ra_proc_macro/src/lib.rs b/crates/ra_proc_macro/src/lib.rs
index 5e21dd487..51fbb046a 100644
--- a/crates/ra_proc_macro/src/lib.rs
+++ b/crates/ra_proc_macro/src/lib.rs
@@ -5,55 +5,104 @@
 //! is used to provide basic infrastructure  for communication between two
 //! processes: Client (RA itself), Server (the external program)
 
+mod rpc;
+mod process;
+pub mod msg;
+
+use process::{ProcMacroProcessSrv, ProcMacroProcessThread};
 use ra_tt::{SmolStr, Subtree};
+use rpc::ProcMacroKind;
 use std::{
     path::{Path, PathBuf},
     sync::Arc,
 };
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+pub use rpc::{ExpansionResult, ExpansionTask};
+
+#[derive(Debug, Clone)]
 pub struct ProcMacroProcessExpander {
     process: Arc<ProcMacroProcessSrv>,
+    dylib_path: PathBuf,
     name: SmolStr,
 }
 
+impl Eq for ProcMacroProcessExpander {}
+impl PartialEq for ProcMacroProcessExpander {
+    fn eq(&self, other: &Self) -> bool {
+        self.name == other.name
+            && self.dylib_path == other.dylib_path
+            && Arc::ptr_eq(&self.process, &other.process)
+    }
+}
+
 impl ra_tt::TokenExpander for ProcMacroProcessExpander {
     fn expand(
         &self,
-        _subtree: &Subtree,
+        subtree: &Subtree,
         _attr: Option<&Subtree>,
     ) -> Result<Subtree, ra_tt::ExpansionError> {
-        // FIXME: do nothing for now
-        Ok(Subtree::default())
+        self.process.custom_derive(&self.dylib_path, subtree, &self.name)
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct ProcMacroProcessSrv {
-    path: PathBuf,
+#[derive(Debug)]
+enum ProcMacroClientKind {
+    Process { process: Arc<ProcMacroProcessSrv>, thread: ProcMacroProcessThread },
+    Dummy,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum ProcMacroClient {
-    Process { process: Arc<ProcMacroProcessSrv> },
-    Dummy,
+#[derive(Debug)]
+pub struct ProcMacroClient {
+    kind: ProcMacroClientKind,
 }
 
 impl ProcMacroClient {
-    pub fn extern_process(process_path: &Path) -> ProcMacroClient {
-        let process = ProcMacroProcessSrv { path: process_path.into() };
-        ProcMacroClient::Process { process: Arc::new(process) }
+    pub fn extern_process(process_path: &Path) -> Result<ProcMacroClient, std::io::Error> {
+        let (thread, process) = ProcMacroProcessSrv::run(process_path)?;
+        Ok(ProcMacroClient {
+            kind: ProcMacroClientKind::Process { process: Arc::new(process), thread },
+        })
     }
 
     pub fn dummy() -> ProcMacroClient {
-        ProcMacroClient::Dummy
+        ProcMacroClient { kind: ProcMacroClientKind::Dummy }
     }
 
     pub fn by_dylib_path(
         &self,
-        _dylib_path: &Path,
+        dylib_path: &Path,
     ) -> Vec<(SmolStr, Arc<dyn ra_tt::TokenExpander>)> {
-        // FIXME: return empty for now
-        vec![]
+        match &self.kind {
+            ProcMacroClientKind::Dummy => vec![],
+            ProcMacroClientKind::Process { process, .. } => {
+                let macros = match process.find_proc_macros(dylib_path) {
+                    Err(err) => {
+                        eprintln!("Fail to find proc macro. Error: {:#?}", err);
+                        return vec![];
+                    }
+                    Ok(macros) => macros,
+                };
+
+                macros
+                    .into_iter()
+                    .filter_map(|(name, kind)| {
+                        // FIXME: Support custom derive only for now.
+                        match kind {
+                            ProcMacroKind::CustomDerive => {
+                                let name = SmolStr::new(&name);
+                                let expander: Arc<dyn ra_tt::TokenExpander> =
+                                    Arc::new(ProcMacroProcessExpander {
+                                        process: process.clone(),
+                                        name: name.clone(),
+                                        dylib_path: dylib_path.into(),
+                                    });
+                                Some((name, expander))
+                            }
+                            _ => None,
+                        }
+                    })
+                    .collect()
+            }
+        }
     }
 }
diff --git a/crates/ra_proc_macro/src/msg.rs b/crates/ra_proc_macro/src/msg.rs
new file mode 100644
index 000000000..aa95bcc8f
--- /dev/null
+++ b/crates/ra_proc_macro/src/msg.rs
@@ -0,0 +1,93 @@
+//! Defines messages for cross-process message based on `ndjson` wire protocol
+
+use std::{
+    convert::TryFrom,
+    io::{self, BufRead, Write},
+};
+
+use crate::{
+    rpc::{ListMacrosResult, ListMacrosTask},
+    ExpansionResult, ExpansionTask,
+};
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub enum Request {
+    ListMacro(ListMacrosTask),
+    ExpansionMacro(ExpansionTask),
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub enum Response {
+    Error(ResponseError),
+    ListMacro(ListMacrosResult),
+    ExpansionMacro(ExpansionResult),
+}
+
+macro_rules! impl_try_from_response {
+    ($ty:ty, $tag:ident) => {
+        impl TryFrom<Response> for $ty {
+            type Error = &'static str;
+            fn try_from(value: Response) -> Result<Self, Self::Error> {
+                match value {
+                    Response::$tag(res) => Ok(res),
+                    _ => Err("Fail to convert from response"),
+                }
+            }
+        }
+    };
+}
+
+impl_try_from_response!(ListMacrosResult, ListMacro);
+impl_try_from_response!(ExpansionResult, ExpansionMacro);
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct ResponseError {
+    pub code: ErrorCode,
+    pub message: String,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub enum ErrorCode {
+    ServerErrorEnd,
+    ExpansionError,
+}
+
+pub trait Message: Sized + Serialize + DeserializeOwned {
+    fn read(r: &mut impl BufRead) -> io::Result<Option<Self>> {
+        let text = match read_json(r)? {
+            None => return Ok(None),
+            Some(text) => text,
+        };
+        let msg = serde_json::from_str(&text)?;
+        Ok(Some(msg))
+    }
+    fn write(self, w: &mut impl Write) -> io::Result<()> {
+        let text = serde_json::to_string(&self)?;
+        write_json(w, &text)
+    }
+}
+
+impl Message for Request {}
+impl Message for Response {}
+
+fn read_json(inp: &mut impl BufRead) -> io::Result<Option<String>> {
+    let mut buf = String::new();
+    if inp.read_line(&mut buf)? == 0 {
+        return Ok(None);
+    }
+    // Remove ending '\n'
+    let buf = &buf[..buf.len() - 1];
+    if buf.is_empty() {
+        return Ok(None);
+    }
+    Ok(Some(buf.to_string()))
+}
+
+fn write_json(out: &mut impl Write, msg: &str) -> io::Result<()> {
+    log::debug!("> {}", msg);
+    out.write_all(msg.as_bytes())?;
+    out.write_all(b"\n")?;
+    out.flush()?;
+    Ok(())
+}
diff --git a/crates/ra_proc_macro/src/process.rs b/crates/ra_proc_macro/src/process.rs
new file mode 100644
index 000000000..e8c85be38
--- /dev/null
+++ b/crates/ra_proc_macro/src/process.rs
@@ -0,0 +1,196 @@
+//! Handle process life-time and message passing for proc-macro client
+
+use crossbeam_channel::{bounded, Receiver, Sender};
+use ra_tt::Subtree;
+
+use crate::msg::{ErrorCode, Message, Request, Response, ResponseError};
+use crate::rpc::{ExpansionResult, ExpansionTask, ListMacrosResult, ListMacrosTask, ProcMacroKind};
+
+use io::{BufRead, BufReader};
+use std::{
+    convert::{TryFrom, TryInto},
+    io::{self, Write},
+    path::{Path, PathBuf},
+    process::{Child, Command, Stdio},
+    sync::{Arc, Weak},
+};
+
+#[derive(Debug, Default)]
+pub(crate) struct ProcMacroProcessSrv {
+    inner: Option<Weak<Sender<Task>>>,
+}
+
+#[derive(Debug)]
+pub(crate) struct ProcMacroProcessThread {
+    // XXX: drop order is significant
+    sender: Arc<Sender<Task>>,
+    handle: jod_thread::JoinHandle<()>,
+}
+
+struct Task {
+    req: Request,
+    result_tx: Sender<Option<Response>>,
+}
+
+struct Process {
+    path: PathBuf,
+    child: Child,
+}
+
+impl Drop for Process {
+    fn drop(&mut self) {
+        let _ = self.child.kill();
+    }
+}
+
+impl Process {
+    fn run(process_path: &Path) -> Result<Process, io::Error> {
+        let child = Command::new(process_path.clone())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::null())
+            .spawn()?;
+
+        Ok(Process { path: process_path.into(), child })
+    }
+
+    fn restart(&mut self) -> Result<(), io::Error> {
+        let _ = self.child.kill();
+        self.child = Command::new(self.path.clone())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::null())
+            .spawn()?;
+        Ok(())
+    }
+
+    fn stdio(&mut self) -> Option<(impl Write, impl BufRead)> {
+        let stdin = self.child.stdin.take()?;
+        let stdout = self.child.stdout.take()?;
+        let read = BufReader::new(stdout);
+
+        Some((stdin, read))
+    }
+}
+
+impl ProcMacroProcessSrv {
+    pub fn run(
+        process_path: &Path,
+    ) -> Result<(ProcMacroProcessThread, ProcMacroProcessSrv), io::Error> {
+        let process = Process::run(process_path)?;
+
+        let (task_tx, task_rx) = bounded(0);
+        let handle = jod_thread::spawn(move || {
+            client_loop(task_rx, process);
+        });
+
+        let task_tx = Arc::new(task_tx);
+        let srv = ProcMacroProcessSrv { inner: Some(Arc::downgrade(&task_tx)) };
+        let thread = ProcMacroProcessThread { handle, sender: task_tx };
+
+        Ok((thread, srv))
+    }
+
+    pub fn find_proc_macros(
+        &self,
+        dylib_path: &Path,
+    ) -> Result<Vec<(String, ProcMacroKind)>, ra_tt::ExpansionError> {
+        let task = ListMacrosTask { lib: dylib_path.to_path_buf() };
+
+        let result: ListMacrosResult = self.send_task(Request::ListMacro(task))?;
+        Ok(result.macros)
+    }
+
+    pub fn custom_derive(
+        &self,
+        dylib_path: &Path,
+        subtree: &Subtree,
+        derive_name: &str,
+    ) -> Result<Subtree, ra_tt::ExpansionError> {
+        let task = ExpansionTask {
+            macro_body: subtree.clone(),
+            macro_name: derive_name.to_string(),
+            attributes: None,
+            lib: dylib_path.to_path_buf(),
+        };
+
+        let result: ExpansionResult = self.send_task(Request::ExpansionMacro(task))?;
+        Ok(result.expansion)
+    }
+
+    pub fn send_task<R>(&self, req: Request) -> Result<R, ra_tt::ExpansionError>
+    where
+        R: TryFrom<Response, Error = &'static str>,
+    {
+        let sender = match &self.inner {
+            None => return Err(ra_tt::ExpansionError::Unknown("No sender is found.".to_string())),
+            Some(it) => it,
+        };
+
+        let (result_tx, result_rx) = bounded(0);
+        let sender = match sender.upgrade() {
+            None => {
+                return Err(ra_tt::ExpansionError::Unknown("Proc macro process is closed.".into()))
+            }
+            Some(it) => it,
+        };
+        sender.send(Task { req: req.into(), result_tx }).unwrap();
+        let res = result_rx
+            .recv()
+            .map_err(|_| ra_tt::ExpansionError::Unknown("Proc macro thread is closed.".into()))?;
+
+        match res {
+            Some(Response::Error(err)) => {
+                return Err(ra_tt::ExpansionError::ExpansionError(err.message));
+            }
+            Some(res) => Ok(res.try_into().map_err(|err| {
+                ra_tt::ExpansionError::Unknown(format!(
+                    "Fail to get response, reason : {:#?} ",
+                    err
+                ))
+            })?),
+            None => Err(ra_tt::ExpansionError::Unknown("Empty result".into())),
+        }
+    }
+}
+
+fn client_loop(task_rx: Receiver<Task>, mut process: Process) {
+    let (mut stdin, mut stdout) = match process.stdio() {
+        None => return,
+        Some(it) => it,
+    };
+
+    for task in task_rx {
+        let Task { req, result_tx } = task;
+
+        match send_request(&mut stdin, &mut stdout, req) {
+            Ok(res) => result_tx.send(res).unwrap(),
+            Err(_err) => {
+                let res = Response::Error(ResponseError {
+                    code: ErrorCode::ServerErrorEnd,
+                    message: "Server closed".into(),
+                });
+                result_tx.send(res.into()).unwrap();
+                // Restart the process
+                if process.restart().is_err() {
+                    break;
+                }
+                let stdio = match process.stdio() {
+                    None => break,
+                    Some(it) => it,
+                };
+                stdin = stdio.0;
+                stdout = stdio.1;
+            }
+        }
+    }
+}
+
+fn send_request(
+    mut writer: &mut impl Write,
+    mut reader: &mut impl BufRead,
+    req: Request,
+) -> Result<Option<Response>, io::Error> {
+    req.write(&mut writer)?;
+    Ok(Response::read(&mut reader)?)
+}
diff --git a/crates/ra_proc_macro/src/rpc.rs b/crates/ra_proc_macro/src/rpc.rs
new file mode 100644
index 000000000..66b3f55db
--- /dev/null
+++ b/crates/ra_proc_macro/src/rpc.rs
@@ -0,0 +1,266 @@
+//! Data struture serialization related stuffs for RPC
+//!
+//! Define all necessary rpc serialization data structure,
+//! which include ra_tt related data and some task messages.
+//! Although adding Serialize and Deserialize trait to ra_tt directly seem to be much easier,
+//! we deliberately duplicate the ra_tt struct with #[serde(with = "XXDef")]
+//! for separation of code responsibility.
+
+use ra_tt::{
+    Delimiter, DelimiterKind, Ident, Leaf, Literal, Punct, SmolStr, Spacing, Subtree, TokenId,
+    TokenTree,
+};
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Clone, Eq, PartialEq, Debug, Serialize, Deserialize)]
+pub struct ListMacrosTask {
+    pub lib: PathBuf,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Serialize, Deserialize)]
+pub enum ProcMacroKind {
+    CustomDerive,
+    FuncLike,
+    Attr,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Default, Serialize, Deserialize)]
+pub struct ListMacrosResult {
+    pub macros: Vec<(String, ProcMacroKind)>,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Serialize, Deserialize)]
+pub struct ExpansionTask {
+    /// Argument of macro call.
+    ///
+    /// In custom derive that would be a struct or enum; in attribute-like macro - underlying
+    /// item; in function-like macro - the macro body.
+    #[serde(with = "SubtreeDef")]
+    pub macro_body: Subtree,
+
+    /// Names of macros to expand.
+    ///
+    /// In custom derive those are names of derived traits (`Serialize`, `Getters`, etc.). In
+    /// attribute-like and functiona-like macros - single name of macro itself (`show_streams`).
+    pub macro_name: String,
+
+    /// Possible attributes for the attribute-like macros.
+    #[serde(with = "opt_subtree_def")]
+    pub attributes: Option<Subtree>,
+
+    pub lib: PathBuf,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Default, Serialize, Deserialize)]
+pub struct ExpansionResult {
+    #[serde(with = "SubtreeDef")]
+    pub expansion: Subtree,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "DelimiterKind")]
+enum DelimiterKindDef {
+    Parenthesis,
+    Brace,
+    Bracket,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "TokenId")]
+struct TokenIdDef(u32);
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Delimiter")]
+struct DelimiterDef {
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+    #[serde(with = "DelimiterKindDef")]
+    pub kind: DelimiterKind,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Subtree")]
+struct SubtreeDef {
+    #[serde(default, with = "opt_delimiter_def")]
+    pub delimiter: Option<Delimiter>,
+    #[serde(with = "vec_token_tree")]
+    pub token_trees: Vec<TokenTree>,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "TokenTree")]
+enum TokenTreeDef {
+    #[serde(with = "LeafDef")]
+    Leaf(Leaf),
+    #[serde(with = "SubtreeDef")]
+    Subtree(Subtree),
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Leaf")]
+enum LeafDef {
+    #[serde(with = "LiteralDef")]
+    Literal(Literal),
+    #[serde(with = "PunctDef")]
+    Punct(Punct),
+    #[serde(with = "IdentDef")]
+    Ident(Ident),
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Literal")]
+struct LiteralDef {
+    pub text: SmolStr,
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Punct")]
+struct PunctDef {
+    pub char: char,
+    #[serde(with = "SpacingDef")]
+    pub spacing: Spacing,
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Spacing")]
+enum SpacingDef {
+    Alone,
+    Joint,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Ident")]
+struct IdentDef {
+    pub text: SmolStr,
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+}
+
+mod opt_delimiter_def {
+    use super::{Delimiter, DelimiterDef};
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S>(value: &Option<Delimiter>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        #[derive(Serialize)]
+        struct Helper<'a>(#[serde(with = "DelimiterDef")] &'a Delimiter);
+        value.as_ref().map(Helper).serialize(serializer)
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Option<Delimiter>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct Helper(#[serde(with = "DelimiterDef")] Delimiter);
+        let helper = Option::deserialize(deserializer)?;
+        Ok(helper.map(|Helper(external)| external))
+    }
+}
+
+mod opt_subtree_def {
+    use super::{Subtree, SubtreeDef};
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S>(value: &Option<Subtree>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        #[derive(Serialize)]
+        struct Helper<'a>(#[serde(with = "SubtreeDef")] &'a Subtree);
+        value.as_ref().map(Helper).serialize(serializer)
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Option<Subtree>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct Helper(#[serde(with = "SubtreeDef")] Subtree);
+        let helper = Option::deserialize(deserializer)?;
+        Ok(helper.map(|Helper(external)| external))
+    }
+}
+
+mod vec_token_tree {
+    use super::{TokenTree, TokenTreeDef};
+    use serde::{ser::SerializeSeq, Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S>(value: &Vec<TokenTree>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        #[derive(Serialize)]
+        struct Helper<'a>(#[serde(with = "TokenTreeDef")] &'a TokenTree);
+
+        let items: Vec<_> = value.iter().map(Helper).collect();
+        let mut seq = serializer.serialize_seq(Some(items.len()))?;
+        for element in items {
+            seq.serialize_element(&element)?;
+        }
+        seq.end()
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<TokenTree>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct Helper(#[serde(with = "TokenTreeDef")] TokenTree);
+
+        let helper = Vec::deserialize(deserializer)?;
+        Ok(helper.into_iter().map(|Helper(external)| external).collect())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn fixture_token_tree() -> Subtree {
+        let mut subtree = Subtree::default();
+        subtree
+            .token_trees
+            .push(TokenTree::Leaf(Ident { text: "struct".into(), id: TokenId(0) }.into()));
+        subtree
+            .token_trees
+            .push(TokenTree::Leaf(Ident { text: "Foo".into(), id: TokenId(1) }.into()));
+        subtree.token_trees.push(TokenTree::Subtree(
+            Subtree {
+                delimiter: Some(Delimiter { id: TokenId(2), kind: DelimiterKind::Brace }),
+                token_trees: vec![],
+            }
+            .into(),
+        ));
+        subtree
+    }
+
+    #[test]
+    fn test_proc_macro_rpc_works() {
+        let tt = fixture_token_tree();
+        let task = ExpansionTask {
+            macro_body: tt.clone(),
+            macro_name: Default::default(),
+            attributes: None,
+            lib: Default::default(),
+        };
+
+        let json = serde_json::to_string(&task).unwrap();
+        let back: ExpansionTask = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(task.macro_body, back.macro_body);
+
+        let result = ExpansionResult { expansion: tt.clone() };
+        let json = serde_json::to_string(&result).unwrap();
+        let back: ExpansionResult = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(result, back);
+    }
+}
diff --git a/crates/ra_prof/src/lib.rs b/crates/ra_prof/src/lib.rs
index 9e167db96..00ea3a9b0 100644
--- a/crates/ra_prof/src/lib.rs
+++ b/crates/ra_prof/src/lib.rs
@@ -339,6 +339,14 @@ pub fn print_backtrace() {
     let bt = backtrace::Backtrace::new();
     eprintln!("{:?}", bt);
 }
+#[cfg(not(feature = "backtrace"))]
+pub fn print_backtrace() {
+    eprintln!(
+        r#"enable the backtrace feature:
+    ra_prof = {{ path = "../ra_prof", features = [ "backtrace"] }}
+"#
+    );
+}
 
 thread_local!(static IN_SCOPE: RefCell<bool> = RefCell::new(false));
 
diff --git a/crates/ra_project_model/Cargo.toml b/crates/ra_project_model/Cargo.toml
index cdcdd63c9..b10644b4b 100644
--- a/crates/ra_project_model/Cargo.toml
+++ b/crates/ra_project_model/Cargo.toml
@@ -16,7 +16,6 @@ cargo_metadata = "0.9.1"
 ra_arena = { path = "../ra_arena" }
 ra_db = { path = "../ra_db" }
 ra_cfg = { path = "../ra_cfg" }
-ra_cargo_watch = { path = "../ra_cargo_watch" }
 ra_proc_macro =  { path = "../ra_proc_macro" }
 
 serde = { version = "1.0.104", features = ["derive"] }
diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index 291594e2a..b50cda06f 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -1,17 +1,18 @@
 //! FIXME: write short doc here
 
 use std::{
+    env,
+    ffi::OsStr,
     ops,
     path::{Path, PathBuf},
+    process::Command,
 };
 
 use anyhow::{Context, Result};
 use cargo_metadata::{BuildScript, CargoOpt, Message, MetadataCommand, PackageId};
 use ra_arena::{Arena, Idx};
-use ra_cargo_watch::run_cargo;
 use ra_db::Edition;
 use rustc_hash::FxHashMap;
-use serde::Deserialize;
 
 /// `CargoWorkspace` represents the logical structure of, well, a Cargo
 /// workspace. It pretty closely mirrors `cargo metadata` output.
@@ -41,9 +42,8 @@ impl ops::Index<Target> for CargoWorkspace {
     }
 }
 
-#[derive(Deserialize, Clone, Debug, PartialEq, Eq)]
-#[serde(rename_all = "camelCase", default)]
-pub struct CargoFeatures {
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct CargoConfig {
     /// Do not activate the `default` feature.
     pub no_default_features: bool,
 
@@ -58,9 +58,9 @@ pub struct CargoFeatures {
     pub load_out_dirs_from_check: bool,
 }
 
-impl Default for CargoFeatures {
+impl Default for CargoConfig {
     fn default() -> Self {
-        CargoFeatures {
+        CargoConfig {
             no_default_features: false,
             all_features: true,
             features: Vec::new(),
@@ -75,6 +75,7 @@ pub type Target = Idx<TargetData>;
 
 #[derive(Debug, Clone)]
 pub struct PackageData {
+    pub version: String,
     pub name: String,
     pub manifest: PathBuf,
     pub targets: Vec<Target>,
@@ -138,7 +139,7 @@ impl PackageData {
 impl CargoWorkspace {
     pub fn from_cargo_metadata(
         cargo_toml: &Path,
-        cargo_features: &CargoFeatures,
+        cargo_features: &CargoConfig,
     ) -> Result<CargoWorkspace> {
         let mut meta = MetadataCommand::new();
         meta.manifest_path(cargo_toml);
@@ -161,7 +162,7 @@ impl CargoWorkspace {
         let mut out_dir_by_id = FxHashMap::default();
         let mut proc_macro_dylib_paths = FxHashMap::default();
         if cargo_features.load_out_dirs_from_check {
-            let resources = load_extern_resources(cargo_toml, cargo_features);
+            let resources = load_extern_resources(cargo_toml, cargo_features)?;
             out_dir_by_id = resources.out_dirs;
             proc_macro_dylib_paths = resources.proc_dylib_paths;
         }
@@ -173,13 +174,15 @@ impl CargoWorkspace {
         let ws_members = &meta.workspace_members;
 
         for meta_pkg in meta.packages {
-            let cargo_metadata::Package { id, edition, name, manifest_path, .. } = meta_pkg;
+            let cargo_metadata::Package { id, edition, name, manifest_path, version, .. } =
+                meta_pkg;
             let is_member = ws_members.contains(&id);
             let edition = edition
                 .parse::<Edition>()
                 .with_context(|| format!("Failed to parse edition {}", edition))?;
             let pkg = packages.alloc(PackageData {
                 name,
+                version: version.to_string(),
                 manifest: manifest_path,
                 targets: Vec::new(),
                 is_member,
@@ -249,6 +252,18 @@ impl CargoWorkspace {
     pub fn workspace_root(&self) -> &Path {
         &self.workspace_root
     }
+
+    pub fn package_flag(&self, package: &PackageData) -> String {
+        if self.is_unique(&*package.name) {
+            package.name.clone()
+        } else {
+            format!("{}:{}", package.name, package.version)
+        }
+    }
+
+    fn is_unique(&self, name: &str) -> bool {
+        self.packages.iter().filter(|(_, v)| v.name == name).count() == 1
+    }
 }
 
 #[derive(Debug, Clone, Default)]
@@ -257,48 +272,60 @@ pub struct ExternResources {
     proc_dylib_paths: FxHashMap<PackageId, PathBuf>,
 }
 
-pub fn load_extern_resources(cargo_toml: &Path, cargo_features: &CargoFeatures) -> ExternResources {
-    let mut args: Vec<String> = vec![
-        "check".to_string(),
-        "--message-format=json".to_string(),
-        "--manifest-path".to_string(),
-        cargo_toml.display().to_string(),
-    ];
-
+pub fn load_extern_resources(
+    cargo_toml: &Path,
+    cargo_features: &CargoConfig,
+) -> Result<ExternResources> {
+    let mut cmd = Command::new(cargo_binary());
+    cmd.args(&["check", "--message-format=json", "--manifest-path"]).arg(cargo_toml);
     if cargo_features.all_features {
-        args.push("--all-features".to_string());
+        cmd.arg("--all-features");
     } else if cargo_features.no_default_features {
         // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
         // https://github.com/oli-obk/cargo_metadata/issues/79
-        args.push("--no-default-features".to_string());
+        cmd.arg("--no-default-features");
     } else {
-        args.extend(cargo_features.features.iter().cloned());
+        cmd.args(&cargo_features.features);
     }
 
-    let mut acc = ExternResources::default();
-    let res = run_cargo(&args, cargo_toml.parent(), &mut |message| {
-        match message {
-            Message::BuildScriptExecuted(BuildScript { package_id, out_dir, .. }) => {
-                acc.out_dirs.insert(package_id, out_dir);
-            }
+    let output = cmd.output()?;
 
-            Message::CompilerArtifact(message) => {
-                if message.target.kind.contains(&"proc-macro".to_string()) {
-                    let package_id = message.package_id;
-                    if let Some(filename) = message.filenames.get(0) {
-                        acc.proc_dylib_paths.insert(package_id, filename.clone());
+    let mut res = ExternResources::default();
+
+    for message in cargo_metadata::parse_messages(output.stdout.as_slice()) {
+        if let Ok(message) = message {
+            match message {
+                Message::BuildScriptExecuted(BuildScript { package_id, out_dir, .. }) => {
+                    res.out_dirs.insert(package_id, out_dir);
+                }
+
+                Message::CompilerArtifact(message) => {
+                    if message.target.kind.contains(&"proc-macro".to_string()) {
+                        let package_id = message.package_id;
+                        // Skip rmeta file
+                        if let Some(filename) =
+                            message.filenames.iter().filter(|name| is_dylib(name)).next()
+                        {
+                            res.proc_dylib_paths.insert(package_id, filename.clone());
+                        }
                     }
                 }
+                Message::CompilerMessage(_) => (),
+                Message::Unknown => (),
             }
-            Message::CompilerMessage(_) => (),
-            Message::Unknown => (),
         }
-        true
-    });
+    }
+    Ok(res)
+}
 
-    if let Err(err) = res {
-        log::error!("Failed to load outdirs: {:?}", err);
+// FIXME: File a better way to know if it is a dylib
+fn is_dylib(path: &Path) -> bool {
+    match path.extension().and_then(OsStr::to_str).map(|it| it.to_string().to_lowercase()) {
+        None => false,
+        Some(ext) => matches!(ext.as_str(), "dll" | "dylib" | "so"),
     }
+}
 
-    acc
+fn cargo_binary() -> String {
+    env::var("CARGO").unwrap_or_else(|_| "cargo".to_string())
 }
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index 444d3bb3f..0ab64a1e0 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -19,7 +19,7 @@ use rustc_hash::FxHashMap;
 use serde_json::from_reader;
 
 pub use crate::{
-    cargo_workspace::{CargoFeatures, CargoWorkspace, Package, Target, TargetKind},
+    cargo_workspace::{CargoConfig, CargoWorkspace, Package, Target, TargetKind},
     json_project::JsonProject,
     sysroot::Sysroot,
 };
@@ -62,30 +62,30 @@ pub struct PackageRoot {
     /// Is a member of the current workspace
     is_member: bool,
 }
-
 impl PackageRoot {
-    pub fn new(path: PathBuf, is_member: bool) -> PackageRoot {
-        PackageRoot { path, is_member }
+    pub fn new_member(path: PathBuf) -> PackageRoot {
+        Self { path, is_member: true }
     }
-
-    pub fn path(&self) -> &PathBuf {
+    pub fn new_non_member(path: PathBuf) -> PackageRoot {
+        Self { path, is_member: false }
+    }
+    pub fn path(&self) -> &Path {
         &self.path
     }
-
     pub fn is_member(&self) -> bool {
         self.is_member
     }
 }
 
 impl ProjectWorkspace {
-    pub fn discover(path: &Path, cargo_features: &CargoFeatures) -> Result<ProjectWorkspace> {
+    pub fn discover(path: &Path, cargo_features: &CargoConfig) -> Result<ProjectWorkspace> {
         ProjectWorkspace::discover_with_sysroot(path, true, cargo_features)
     }
 
     pub fn discover_with_sysroot(
         path: &Path,
         with_sysroot: bool,
-        cargo_features: &CargoFeatures,
+        cargo_features: &CargoConfig,
     ) -> Result<ProjectWorkspace> {
         match find_rust_project_json(path) {
             Some(json_path) => {
@@ -130,70 +130,45 @@ impl ProjectWorkspace {
     pub fn to_roots(&self) -> Vec<PackageRoot> {
         match self {
             ProjectWorkspace::Json { project } => {
-                let mut roots = Vec::with_capacity(project.roots.len());
-                for root in &project.roots {
-                    roots.push(PackageRoot::new(root.path.clone(), true));
-                }
-                roots
-            }
-            ProjectWorkspace::Cargo { cargo, sysroot } => {
-                let mut roots = Vec::with_capacity(cargo.packages().len() + sysroot.crates().len());
-                for pkg in cargo.packages() {
-                    let root = cargo[pkg].root().to_path_buf();
-                    let member = cargo[pkg].is_member;
-                    roots.push(PackageRoot::new(root, member));
-                }
-                for krate in sysroot.crates() {
-                    roots.push(PackageRoot::new(sysroot[krate].root_dir().to_path_buf(), false))
-                }
-                roots
+                project.roots.iter().map(|r| PackageRoot::new_member(r.path.clone())).collect()
             }
+            ProjectWorkspace::Cargo { cargo, sysroot } => cargo
+                .packages()
+                .map(|pkg| PackageRoot {
+                    path: cargo[pkg].root().to_path_buf(),
+                    is_member: cargo[pkg].is_member,
+                })
+                .chain(sysroot.crates().map(|krate| {
+                    PackageRoot::new_non_member(sysroot[krate].root_dir().to_path_buf())
+                }))
+                .collect(),
         }
     }
 
     pub fn out_dirs(&self) -> Vec<PathBuf> {
         match self {
             ProjectWorkspace::Json { project } => {
-                let mut out_dirs = Vec::with_capacity(project.crates.len());
-                for krate in &project.crates {
-                    if let Some(out_dir) = &krate.out_dir {
-                        out_dirs.push(out_dir.to_path_buf());
-                    }
-                }
-                out_dirs
+                project.crates.iter().filter_map(|krate| krate.out_dir.as_ref()).cloned().collect()
             }
-            ProjectWorkspace::Cargo { cargo, sysroot: _sysroot } => {
-                let mut out_dirs = Vec::with_capacity(cargo.packages().len());
-                for pkg in cargo.packages() {
-                    if let Some(out_dir) = &cargo[pkg].out_dir {
-                        out_dirs.push(out_dir.to_path_buf());
-                    }
-                }
-                out_dirs
+            ProjectWorkspace::Cargo { cargo, sysroot: _ } => {
+                cargo.packages().filter_map(|pkg| cargo[pkg].out_dir.as_ref()).cloned().collect()
             }
         }
     }
 
     pub fn proc_macro_dylib_paths(&self) -> Vec<PathBuf> {
         match self {
-            ProjectWorkspace::Json { project } => {
-                let mut proc_macro_dylib_paths = Vec::with_capacity(project.crates.len());
-                for krate in &project.crates {
-                    if let Some(out_dir) = &krate.proc_macro_dylib_path {
-                        proc_macro_dylib_paths.push(out_dir.to_path_buf());
-                    }
-                }
-                proc_macro_dylib_paths
-            }
-            ProjectWorkspace::Cargo { cargo, sysroot: _sysroot } => {
-                let mut proc_macro_dylib_paths = Vec::with_capacity(cargo.packages().len());
-                for pkg in cargo.packages() {
-                    if let Some(dylib_path) = &cargo[pkg].proc_macro_dylib_path {
-                        proc_macro_dylib_paths.push(dylib_path.to_path_buf());
-                    }
-                }
-                proc_macro_dylib_paths
-            }
+            ProjectWorkspace::Json { project } => project
+                .crates
+                .iter()
+                .filter_map(|krate| krate.proc_macro_dylib_path.as_ref())
+                .cloned()
+                .collect(),
+            ProjectWorkspace::Cargo { cargo, sysroot: _sysroot } => cargo
+                .packages()
+                .filter_map(|pkg| cargo[pkg].proc_macro_dylib_path.as_ref())
+                .cloned()
+                .collect(),
         }
     }
 
@@ -216,10 +191,12 @@ impl ProjectWorkspace {
         let mut crate_graph = CrateGraph::default();
         match self {
             ProjectWorkspace::Json { project } => {
-                let mut crates = FxHashMap::default();
-                for (id, krate) in project.crates.iter().enumerate() {
-                    let crate_id = json_project::CrateId(id);
-                    if let Some(file_id) = load(&krate.root_module) {
+                let crates: FxHashMap<_, _> = project
+                    .crates
+                    .iter()
+                    .enumerate()
+                    .filter_map(|(seq_index, krate)| {
+                        let file_id = load(&krate.root_module)?;
                         let edition = match krate.edition {
                             json_project::Edition::Edition2015 => Edition::Edition2015,
                             json_project::Edition::Edition2018 => Edition::Edition2018,
@@ -249,8 +226,8 @@ impl ProjectWorkspace {
                             .clone()
                             .map(|it| proc_macro_client.by_dylib_path(&it));
                         // FIXME: No crate name in json definition such that we cannot add OUT_DIR to env
-                        crates.insert(
-                            crate_id,
+                        Some((
+                            json_project::CrateId(seq_index),
                             crate_graph.add_crate_root(
                                 file_id,
                                 edition,
@@ -261,9 +238,9 @@ impl ProjectWorkspace {
                                 extern_source,
                                 proc_macro.unwrap_or_default(),
                             ),
-                        );
-                    }
-                }
+                        ))
+                    })
+                    .collect();
 
                 for (id, krate) in project.crates.iter().enumerate() {
                     for dep in &krate.deps {
@@ -287,9 +264,11 @@ impl ProjectWorkspace {
                 }
             }
             ProjectWorkspace::Cargo { cargo, sysroot } => {
-                let mut sysroot_crates = FxHashMap::default();
-                for krate in sysroot.crates() {
-                    if let Some(file_id) = load(&sysroot[krate].root) {
+                let sysroot_crates: FxHashMap<_, _> = sysroot
+                    .crates()
+                    .filter_map(|krate| {
+                        let file_id = load(&sysroot[krate].root)?;
+
                         // Crates from sysroot have `cfg(test)` disabled
                         let cfg_options = {
                             let mut opts = default_cfg_options.clone();
@@ -300,22 +279,22 @@ impl ProjectWorkspace {
                         let env = Env::default();
                         let extern_source = ExternSource::default();
                         let proc_macro = vec![];
+                        let crate_name = CrateName::new(&sysroot[krate].name)
+                            .expect("Sysroot crate names should not contain dashes");
 
                         let crate_id = crate_graph.add_crate_root(
                             file_id,
                             Edition::Edition2018,
-                            Some(
-                                CrateName::new(&sysroot[krate].name)
-                                    .expect("Sysroot crate names should not contain dashes"),
-                            ),
+                            Some(crate_name),
                             cfg_options,
                             env,
                             extern_source,
                             proc_macro,
                         );
-                        sysroot_crates.insert(krate, crate_id);
-                    }
-                }
+                        Some((krate, crate_id))
+                    })
+                    .collect();
+
                 for from in sysroot.crates() {
                     for &to in sysroot[from].deps.iter() {
                         let name = &sysroot[to].name;
diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
index 2304e00cf..b69cae234 100644
--- a/crates/ra_syntax/src/ast/edit.rs
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -46,14 +46,46 @@ impl ast::FnDef {
     }
 }
 
+fn make_multiline<N>(node: N) -> N
+where
+    N: AstNode + Clone,
+{
+    let l_curly = match node.syntax().children_with_tokens().find(|it| it.kind() == T!['{']) {
+        Some(it) => it,
+        None => return node,
+    };
+    let sibling = match l_curly.next_sibling_or_token() {
+        Some(it) => it,
+        None => return node,
+    };
+    let existing_ws = match sibling.as_token() {
+        None => None,
+        Some(tok) if tok.kind() != WHITESPACE => None,
+        Some(ws) => {
+            if ws.text().contains('\n') {
+                return node;
+            }
+            Some(ws.clone())
+        }
+    };
+
+    let indent = leading_indent(node.syntax()).unwrap_or_default();
+    let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
+    let to_insert = iter::once(ws.ws().into());
+    match existing_ws {
+        None => node.insert_children(InsertPosition::After(l_curly), to_insert),
+        Some(ws) => node.replace_children(single_node(ws), to_insert),
+    }
+}
+
 impl ast::ItemList {
     #[must_use]
-    pub fn append_items(&self, items: impl Iterator<Item = ast::ImplItem>) -> ast::ItemList {
+    pub fn append_items(&self, items: impl IntoIterator<Item = ast::ImplItem>) -> ast::ItemList {
         let mut res = self.clone();
         if !self.syntax().text().contains_char('\n') {
-            res = res.make_multiline();
+            res = make_multiline(res);
         }
-        items.for_each(|it| res = res.append_item(it));
+        items.into_iter().for_each(|it| res = res.append_item(it));
         res
     }
 
@@ -81,35 +113,6 @@ impl ast::ItemList {
     fn l_curly(&self) -> Option<SyntaxElement> {
         self.syntax().children_with_tokens().find(|it| it.kind() == T!['{'])
     }
-
-    fn make_multiline(&self) -> ast::ItemList {
-        let l_curly = match self.syntax().children_with_tokens().find(|it| it.kind() == T!['{']) {
-            Some(it) => it,
-            None => return self.clone(),
-        };
-        let sibling = match l_curly.next_sibling_or_token() {
-            Some(it) => it,
-            None => return self.clone(),
-        };
-        let existing_ws = match sibling.as_token() {
-            None => None,
-            Some(tok) if tok.kind() != WHITESPACE => None,
-            Some(ws) => {
-                if ws.text().contains('\n') {
-                    return self.clone();
-                }
-                Some(ws.clone())
-            }
-        };
-
-        let indent = leading_indent(self.syntax()).unwrap_or_default();
-        let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
-        let to_insert = iter::once(ws.ws().into());
-        match existing_ws {
-            None => self.insert_children(InsertPosition::After(l_curly), to_insert),
-            Some(ws) => self.replace_children(single_node(ws), to_insert),
-        }
-    }
 }
 
 impl ast::RecordFieldList {
@@ -334,6 +337,80 @@ impl ast::UseTree {
     }
 }
 
+impl ast::MatchArmList {
+    #[must_use]
+    pub fn append_arms(&self, items: impl IntoIterator<Item = ast::MatchArm>) -> ast::MatchArmList {
+        let mut res = self.clone();
+        res = res.strip_if_only_whitespace();
+        if !res.syntax().text().contains_char('\n') {
+            res = make_multiline(res);
+        }
+        items.into_iter().for_each(|it| res = res.append_arm(it));
+        res
+    }
+
+    fn strip_if_only_whitespace(&self) -> ast::MatchArmList {
+        let mut iter = self.syntax().children_with_tokens().skip_while(|it| it.kind() != T!['{']);
+        iter.next(); // Eat the curly
+        let mut inner = iter.take_while(|it| it.kind() != T!['}']);
+        if !inner.clone().all(|it| it.kind() == WHITESPACE) {
+            return self.clone();
+        }
+        let start = match inner.next() {
+            Some(s) => s,
+            None => return self.clone(),
+        };
+        let end = match inner.last() {
+            Some(s) => s,
+            None => start.clone(),
+        };
+        self.replace_children(start..=end, &mut iter::empty())
+    }
+
+    #[must_use]
+    pub fn remove_placeholder(&self) -> ast::MatchArmList {
+        let placeholder =
+            self.arms().find(|arm| matches!(arm.pat(), Some(ast::Pat::PlaceholderPat(_))));
+        if let Some(placeholder) = placeholder {
+            self.remove_arm(&placeholder)
+        } else {
+            self.clone()
+        }
+    }
+
+    #[must_use]
+    fn remove_arm(&self, arm: &ast::MatchArm) -> ast::MatchArmList {
+        let start = arm.syntax().clone();
+        let end = if let Some(comma) = start
+            .siblings_with_tokens(Direction::Next)
+            .skip(1)
+            .skip_while(|it| it.kind().is_trivia())
+            .next()
+            .filter(|it| it.kind() == T![,])
+        {
+            comma
+        } else {
+            start.clone().into()
+        };
+        self.replace_children(start.into()..=end, None)
+    }
+
+    #[must_use]
+    pub fn append_arm(&self, item: ast::MatchArm) -> ast::MatchArmList {
+        let r_curly = match self.syntax().children_with_tokens().find(|it| it.kind() == T!['}']) {
+            Some(t) => t,
+            None => return self.clone(),
+        };
+        let position = InsertPosition::Before(r_curly.into());
+        let arm_ws = tokens::WsBuilder::new("    ");
+        let match_indent = &leading_indent(self.syntax()).unwrap_or_default();
+        let match_ws = tokens::WsBuilder::new(&format!("\n{}", match_indent));
+        let to_insert: ArrayVec<[SyntaxElement; 3]> =
+            [arm_ws.ws().into(), item.syntax().clone().into(), match_ws.ws().into()].into();
+        self.insert_children(position, to_insert)
+    }
+}
+
 #[must_use]
 pub fn remove_attrs_and_docs<N: ast::AttrsOwner>(node: &N) -> N {
     N::cast(remove_attrs_and_docs_inner(node.syntax().clone())).unwrap()
diff --git a/crates/ra_syntax/src/ast/expr_extensions.rs b/crates/ra_syntax/src/ast/expr_extensions.rs
index 77cceb382..8bbd946c0 100644
--- a/crates/ra_syntax/src/ast/expr_extensions.rs
+++ b/crates/ra_syntax/src/ast/expr_extensions.rs
@@ -308,7 +308,7 @@ pub enum LiteralKind {
     Byte,
     IntNumber { suffix: Option<SmolStr> },
     FloatNumber { suffix: Option<SmolStr> },
-    Bool,
+    Bool(bool),
 }
 
 impl ast::Literal {
@@ -355,7 +355,8 @@ impl ast::Literal {
                 LiteralKind::FloatNumber { suffix: Self::find_suffix(&text, &FLOAT_SUFFIXES) }
             }
             STRING | RAW_STRING => LiteralKind::String,
-            T![true] | T![false] => LiteralKind::Bool,
+            T![true] => LiteralKind::Bool(true),
+            T![false] => LiteralKind::Bool(false),
             BYTE_STRING | RAW_BYTE_STRING => LiteralKind::ByteString,
             CHAR => LiteralKind::Char,
             BYTE => LiteralKind::Byte,
diff --git a/crates/ra_syntax/src/parsing/text_tree_sink.rs b/crates/ra_syntax/src/parsing/text_tree_sink.rs
index dd202601d..87bb21cd9 100644
--- a/crates/ra_syntax/src/parsing/text_tree_sink.rs
+++ b/crates/ra_syntax/src/parsing/text_tree_sink.rs
@@ -149,10 +149,21 @@ fn n_attached_trivias<'a>(
         MACRO_CALL | CONST_DEF | TYPE_ALIAS_DEF | STRUCT_DEF | ENUM_DEF | ENUM_VARIANT | FN_DEF
         | TRAIT_DEF | MODULE | RECORD_FIELD_DEF | STATIC_DEF => {
             let mut res = 0;
-            for (i, (kind, text)) in trivias.enumerate() {
+            let mut trivias = trivias.enumerate().peekable();
+
+            while let Some((i, (kind, text))) = trivias.next() {
                 match kind {
                     WHITESPACE => {
                         if text.contains("\n\n") {
+                            // we check whether the next token is a doc-comment
+                            // and skip the whitespace in this case
+                            if let Some((peek_kind, peek_text)) =
+                                trivias.peek().map(|(_, pair)| pair)
+                            {
+                                if *peek_kind == COMMENT && peek_text.starts_with("///") {
+                                    continue;
+                                }
+                            }
                             break;
                         }
                     }
diff --git a/crates/ra_syntax/test_data/parser/ok/0065_comment_newline.rs b/crates/ra_syntax/test_data/parser/ok/0065_comment_newline.rs
new file mode 100644
index 000000000..1fafe216b
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/ok/0065_comment_newline.rs
@@ -0,0 +1,3 @@
+/// Example
+
+fn test() {}
diff --git a/crates/ra_syntax/test_data/parser/ok/0065_comment_newline.txt b/crates/ra_syntax/test_data/parser/ok/0065_comment_newline.txt
new file mode 100644
index 000000000..91d0c3736
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/ok/0065_comment_newline.txt
@@ -0,0 +1,17 @@
+SOURCE_FILE@[0; 26)
+  FN_DEF@[0; 25)
+    COMMENT@[0; 11) "/// Example"
+    WHITESPACE@[11; 13) "\n\n"
+    FN_KW@[13; 15) "fn"
+    WHITESPACE@[15; 16) " "
+    NAME@[16; 20)
+      IDENT@[16; 20) "test"
+    PARAM_LIST@[20; 22)
+      L_PAREN@[20; 21) "("
+      R_PAREN@[21; 22) ")"
+    WHITESPACE@[22; 23) " "
+    BLOCK_EXPR@[23; 25)
+      BLOCK@[23; 25)
+        L_CURLY@[23; 24) "{"
+        R_CURLY@[24; 25) "}"
+  WHITESPACE@[25; 26) "\n"
diff --git a/crates/ra_tt/src/lib.rs b/crates/ra_tt/src/lib.rs
index 1015ce0a6..bd484aa30 100644
--- a/crates/ra_tt/src/lib.rs
+++ b/crates/ra_tt/src/lib.rs
@@ -189,7 +189,12 @@ impl Subtree {
 pub mod buffer;
 
 #[derive(Debug, PartialEq, Eq)]
-pub enum ExpansionError {}
+pub enum ExpansionError {
+    IOError(String),
+    JsonError(String),
+    Unknown(String),
+    ExpansionError(String),
+}
 
 pub trait TokenExpander: Debug + Send + Sync + RefUnwindSafe {
     fn expand(&self, subtree: &Subtree, attrs: Option<&Subtree>)
diff --git a/crates/rust-analyzer/Cargo.toml b/crates/rust-analyzer/Cargo.toml
index 8fe6799d2..f5f773432 100644
--- a/crates/rust-analyzer/Cargo.toml
+++ b/crates/rust-analyzer/Cargo.toml
@@ -33,7 +33,7 @@ threadpool = "1.7.1"
 stdx = { path = "../stdx" }
 
 lsp-server = "0.3.1"
-ra_cargo_watch = { path = "../ra_cargo_watch" }
+ra_flycheck = { path = "../ra_flycheck" }
 ra_ide = { path = "../ra_ide" }
 ra_prof = { path = "../ra_prof" }
 ra_project_model = { path = "../ra_project_model" }
diff --git a/crates/rust-analyzer/src/bin/main.rs b/crates/rust-analyzer/src/bin/main.rs
index a744a6695..608f4f67b 100644
--- a/crates/rust-analyzer/src/bin/main.rs
+++ b/crates/rust-analyzer/src/bin/main.rs
@@ -4,8 +4,7 @@
 mod args;
 
 use lsp_server::Connection;
-
-use rust_analyzer::{cli, from_json, show_message, Result, ServerConfig};
+use rust_analyzer::{cli, config::Config, from_json, Result};
 
 use crate::args::HelpPrinted;
 
@@ -78,24 +77,18 @@ fn run_server() -> Result<()> {
         .filter(|workspaces| !workspaces.is_empty())
         .unwrap_or_else(|| vec![root]);
 
-    let server_config = initialize_params
-        .initialization_options
-        .and_then(|v| {
-            from_json::<ServerConfig>("config", v)
-                .map_err(|e| {
-                    log::error!("{}", e);
-                    show_message(lsp_types::MessageType::Error, e.to_string(), &connection.sender);
-                })
-                .ok()
-        })
-        .unwrap_or_default();
+    let config = {
+        let mut config = Config::default();
+        if let Some(value) = &initialize_params.initialization_options {
+            config.update(value);
+        }
+        if let Some(caps) = &initialize_params.capabilities.text_document {
+            config.update_caps(caps);
+        }
+        config
+    };
 
-    rust_analyzer::main_loop(
-        workspace_roots,
-        initialize_params.capabilities,
-        server_config,
-        connection,
-    )?;
+    rust_analyzer::main_loop(workspace_roots, config, connection)?;
 
     log::info!("shutting down IO...");
     io_threads.join()?;
diff --git a/crates/rust-analyzer/src/cargo_target_spec.rs b/crates/rust-analyzer/src/cargo_target_spec.rs
index f87bdcec5..942c30328 100644
--- a/crates/rust-analyzer/src/cargo_target_spec.rs
+++ b/crates/rust-analyzer/src/cargo_target_spec.rs
@@ -77,7 +77,7 @@ impl CargoTargetSpec {
             ProjectWorkspace::Cargo { cargo, .. } => {
                 let tgt = cargo.target_by_root(&path)?;
                 Some(CargoTargetSpec {
-                    package: cargo[cargo[tgt].package].name.clone(),
+                    package: cargo.package_flag(&cargo[cargo[tgt].package]),
                     target: cargo[tgt].name.clone(),
                     target_kind: cargo[tgt].kind,
                 })
diff --git a/crates/rust-analyzer/src/cli/analysis_bench.rs b/crates/rust-analyzer/src/cli/analysis_bench.rs
index 7164b0ade..7667873d5 100644
--- a/crates/rust-analyzer/src/cli/analysis_bench.rs
+++ b/crates/rust-analyzer/src/cli/analysis_bench.rs
@@ -12,7 +12,7 @@ use ra_db::{
     salsa::{Database, Durability},
     FileId, SourceDatabaseExt,
 };
-use ra_ide::{Analysis, AnalysisChange, AnalysisHost, CompletionOptions, FilePosition, LineCol};
+use ra_ide::{Analysis, AnalysisChange, AnalysisHost, CompletionConfig, FilePosition, LineCol};
 
 use crate::cli::{load_cargo::load_cargo, Verbosity};
 
@@ -102,7 +102,7 @@ pub fn analysis_bench(
             let file_position = FilePosition { file_id, offset };
 
             if is_completion {
-                let options = CompletionOptions::default();
+                let options = CompletionConfig::default();
                 let res = do_work(&mut host, file_id, |analysis| {
                     analysis.completions(file_position, &options)
                 });
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index 832f04226..69133e4e4 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -8,7 +8,7 @@ use crossbeam_channel::{unbounded, Receiver};
 use ra_db::{ExternSourceId, FileId, SourceRootId};
 use ra_ide::{AnalysisChange, AnalysisHost};
 use ra_project_model::{
-    get_rustc_cfg_options, CargoFeatures, PackageRoot, ProcMacroClient, ProjectWorkspace,
+    get_rustc_cfg_options, CargoConfig, PackageRoot, ProcMacroClient, ProjectWorkspace,
 };
 use ra_vfs::{RootEntry, Vfs, VfsChange, VfsTask, Watch};
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -29,15 +29,14 @@ pub(crate) fn load_cargo(
     let root = std::env::current_dir()?.join(root);
     let ws = ProjectWorkspace::discover(
         root.as_ref(),
-        &CargoFeatures { load_out_dirs_from_check, ..Default::default() },
+        &CargoConfig { load_out_dirs_from_check, ..Default::default() },
     )?;
 
     let mut extern_dirs = FxHashSet::default();
     extern_dirs.extend(ws.out_dirs());
 
     let mut project_roots = ws.to_roots();
-    project_roots
-        .extend(extern_dirs.iter().map(|path| PackageRoot::new(path.to_path_buf(), false)));
+    project_roots.extend(extern_dirs.iter().cloned().map(PackageRoot::new_non_member));
 
     let (sender, receiver) = unbounded();
     let sender = Box::new(move |t| sender.send(t).unwrap());
@@ -46,7 +45,7 @@ pub(crate) fn load_cargo(
             .iter()
             .map(|pkg_root| {
                 RootEntry::new(
-                    pkg_root.path().clone(),
+                    pkg_root.path().to_owned(),
                     RustPackageFilterBuilder::default()
                         .set_member(pkg_root.is_member())
                         .into_vfs_filter(),
@@ -58,12 +57,12 @@ pub(crate) fn load_cargo(
     );
 
     let source_roots = roots
-        .iter()
-        .map(|&vfs_root| {
+        .into_iter()
+        .map(|vfs_root| {
             let source_root_id = vfs_root_to_id(vfs_root);
             let project_root = project_roots
                 .iter()
-                .find(|it| it.path() == &vfs.root2path(vfs_root))
+                .find(|it| it.path() == vfs.root2path(vfs_root))
                 .unwrap()
                 .clone();
             (source_root_id, project_root)
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 628ed107e..04f5bb473 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -7,112 +7,191 @@
 //! configure the server itself, feature flags are passed into analysis, and
 //! tweak things like automatic insertion of `()` in completions.
 
-use rustc_hash::FxHashMap;
-
-use ra_project_model::CargoFeatures;
-use serde::{Deserialize, Deserializer};
-
-/// Client provided initialization options
-#[derive(Deserialize, Clone, Debug, PartialEq, Eq)]
-#[serde(rename_all = "camelCase", default)]
-pub struct ServerConfig {
-    /// Whether the client supports our custom highlighting publishing decorations.
-    /// This is different to the highlightingOn setting, which is whether the user
-    /// wants our custom highlighting to be used.
-    ///
-    /// Defaults to `false`
-    #[serde(deserialize_with = "nullable_bool_false")]
-    pub publish_decorations: bool,
-
-    pub exclude_globs: Vec<String>,
-    #[serde(deserialize_with = "nullable_bool_false")]
-    pub use_client_watching: bool,
+use lsp_types::TextDocumentClientCapabilities;
+use ra_flycheck::FlycheckConfig;
+use ra_ide::{CompletionConfig, InlayHintsConfig};
+use ra_project_model::CargoConfig;
+use serde::Deserialize;
 
-    pub lru_capacity: Option<usize>,
+#[derive(Debug, Clone)]
+pub struct Config {
+    pub client_caps: ClientCapsConfig,
 
-    #[serde(deserialize_with = "nullable_bool_true")]
-    pub inlay_hints_type: bool,
-    #[serde(deserialize_with = "nullable_bool_true")]
-    pub inlay_hints_parameter: bool,
-    #[serde(deserialize_with = "nullable_bool_true")]
-    pub inlay_hints_chaining: bool,
-    pub inlay_hints_max_length: Option<usize>,
-
-    pub cargo_watch_enable: bool,
-    pub cargo_watch_args: Vec<String>,
-    pub cargo_watch_command: String,
-    pub cargo_watch_all_targets: bool,
-
-    /// For internal usage to make integrated tests faster.
-    #[serde(deserialize_with = "nullable_bool_true")]
     pub with_sysroot: bool,
+    pub publish_diagnostics: bool,
+    pub lru_capacity: Option<usize>,
+    pub proc_macro_srv: Option<String>,
+    pub files: FilesConfig,
+    pub notifications: NotificationsConfig,
 
-    /// Fine grained feature flags to disable specific features.
-    pub feature_flags: FxHashMap<String, bool>,
+    pub cargo: CargoConfig,
+    pub rustfmt: RustfmtConfig,
+    pub check: Option<FlycheckConfig>,
 
-    pub rustfmt_args: Vec<String>,
+    pub inlay_hints: InlayHintsConfig,
+    pub completion: CompletionConfig,
+    pub call_info_full: bool,
+}
 
-    /// Cargo feature configurations.
-    pub cargo_features: CargoFeatures,
+#[derive(Debug, Clone)]
+pub struct FilesConfig {
+    pub watcher: FilesWatcher,
+    pub exclude: Vec<String>,
+}
 
-    /// Enabled if the vscode_lldb extension is available.
-    pub vscode_lldb: bool,
+#[derive(Debug, Clone)]
+pub enum FilesWatcher {
+    Client,
+    Notify,
 }
 
-impl Default for ServerConfig {
-    fn default() -> ServerConfig {
-        ServerConfig {
-            publish_decorations: false,
-            exclude_globs: Vec::new(),
-            use_client_watching: false,
-            lru_capacity: None,
-            inlay_hints_type: true,
-            inlay_hints_parameter: true,
-            inlay_hints_chaining: true,
-            inlay_hints_max_length: None,
-            cargo_watch_enable: true,
-            cargo_watch_args: Vec::new(),
-            cargo_watch_command: "check".to_string(),
-            cargo_watch_all_targets: true,
+#[derive(Debug, Clone)]
+pub struct NotificationsConfig {
+    pub workspace_loaded: bool,
+    pub cargo_toml_not_found: bool,
+}
+
+#[derive(Debug, Clone)]
+pub enum RustfmtConfig {
+    Rustfmt {
+        extra_args: Vec<String>,
+    },
+    #[allow(unused)]
+    CustomCommand {
+        command: String,
+        args: Vec<String>,
+    },
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct ClientCapsConfig {
+    pub location_link: bool,
+    pub line_folding_only: bool,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Config {
+            client_caps: ClientCapsConfig::default(),
+
             with_sysroot: true,
-            feature_flags: FxHashMap::default(),
-            cargo_features: Default::default(),
-            rustfmt_args: Vec::new(),
-            vscode_lldb: false,
+            publish_diagnostics: true,
+            lru_capacity: None,
+            proc_macro_srv: None,
+            files: FilesConfig { watcher: FilesWatcher::Notify, exclude: Vec::new() },
+            notifications: NotificationsConfig {
+                workspace_loaded: true,
+                cargo_toml_not_found: true,
+            },
+
+            cargo: CargoConfig::default(),
+            rustfmt: RustfmtConfig::Rustfmt { extra_args: Vec::new() },
+            check: Some(FlycheckConfig::CargoCommand {
+                command: "check".to_string(),
+                all_targets: true,
+                extra_args: Vec::new(),
+            }),
+
+            inlay_hints: InlayHintsConfig {
+                type_hints: true,
+                parameter_hints: true,
+                chaining_hints: true,
+                max_length: None,
+            },
+            completion: CompletionConfig {
+                enable_postfix_completions: true,
+                add_call_parenthesis: true,
+                add_call_argument_snippets: true,
+            },
+            call_info_full: true,
         }
     }
 }
 
-/// Deserializes a null value to a bool false by default
-fn nullable_bool_false<'de, D>(deserializer: D) -> Result<bool, D::Error>
-where
-    D: Deserializer<'de>,
-{
-    let opt = Option::deserialize(deserializer)?;
-    Ok(opt.unwrap_or(false))
-}
+impl Config {
+    #[rustfmt::skip]
+    pub fn update(&mut self, value: &serde_json::Value) {
+        log::info!("Config::update({:#})", value);
+
+        let client_caps = self.client_caps.clone();
+        *self = Default::default();
+        self.client_caps = client_caps;
+
+        set(value, "/withSysroot", &mut self.with_sysroot);
+        set(value, "/featureFlags/lsp.diagnostics", &mut self.publish_diagnostics);
+        set(value, "/lruCapacity", &mut self.lru_capacity);
+        if let Some(watcher) =  get::<String>(value, "/files/watcher") {
+            self.files.watcher = match watcher.as_str() {
+                "client" => FilesWatcher::Client,
+                "notify"| _ => FilesWatcher::Notify,
+            }
+        }
+        set(value, "/notifications/workspaceLoaded", &mut self.notifications.workspace_loaded);
+        set(value, "/notifications/cargoTomlNotFound", &mut self.notifications.cargo_toml_not_found);
+
+        set(value, "/cargo/noDefaultFeatures", &mut self.cargo.no_default_features);
+        set(value, "/cargo/allFeatures", &mut self.cargo.all_features);
+        set(value, "/cargo/features", &mut self.cargo.features);
+        set(value, "/cargo/loadOutDirsFromCheck", &mut self.cargo.load_out_dirs_from_check);
+        if let Some(mut args) = get::<Vec<String>>(value, "/rustfmt/overrideCommand") {
+            if !args.is_empty() {
+                let command = args.remove(0);
+                self.rustfmt = RustfmtConfig::CustomCommand {
+                    command,
+                    args,
+                }
+            }
+        } else if let RustfmtConfig::Rustfmt { extra_args } = &mut self.rustfmt {
+            set(value, "/rustfmt/extraArgs", extra_args);
+        }
+        if let Some(false) = get(value, "/checkOnSave/enable") {
+            self.check = None
+        } else {
+            if let Some(mut args) = get::<Vec<String>>(value, "/checkOnSave/overrideCommand") {
+                if !args.is_empty() {
+                    let command = args.remove(0);
+                    self.check = Some(FlycheckConfig::CustomCommand {
+                        command,
+                        args,
+                    })
+                }
+
+            } else if let Some(FlycheckConfig::CargoCommand { command, extra_args, all_targets }) = &mut self.check
+            {
+                set(value, "/checkOnSave/extraArgs", extra_args);
+                set(value, "/checkOnSave/command", command);
+                set(value, "/checkOnSave/allTargets", all_targets);
+            }
+        };
+
+        set(value, "/inlayHints/typeHints", &mut self.inlay_hints.type_hints);
+        set(value, "/inlayHints/parameterHints", &mut self.inlay_hints.parameter_hints);
+        set(value, "/inlayHints/chainingHints", &mut self.inlay_hints.chaining_hints);
+        set(value, "/inlayHints/maxLength", &mut self.inlay_hints.max_length);
+        set(value, "/completion/postfix/enable", &mut self.completion.enable_postfix_completions);
+        set(value, "/completion/addCallParenthesis", &mut self.completion.add_call_parenthesis);
+        set(value, "/completion/addCallArgumentSnippets", &mut self.completion.add_call_argument_snippets);
+        set(value, "/callInfo/full", &mut self.call_info_full);
+
+        log::info!("Config::update() = {:#?}", self);
+
+        fn get<'a, T: Deserialize<'a>>(value: &'a serde_json::Value, pointer: &str) -> Option<T> {
+            value.pointer(pointer).and_then(|it| T::deserialize(it).ok())
+        }
 
-/// Deserializes a null value to a bool true by default
-fn nullable_bool_true<'de, D>(deserializer: D) -> Result<bool, D::Error>
-where
-    D: Deserializer<'de>,
-{
-    let opt = Option::deserialize(deserializer)?;
-    Ok(opt.unwrap_or(true))
-}
+        fn set<'a, T: Deserialize<'a> + std::fmt::Debug>(value: &'a serde_json::Value, pointer: &str, slot: &mut T) {
+            if let Some(new_value) = get(value, pointer) {
+                *slot = new_value
+            }
+        }
+    }
 
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn deserialize_init_options_defaults() {
-        // check that null == default for both fields
-        let default = ServerConfig::default();
-        assert_eq!(default, serde_json::from_str(r#"{}"#).unwrap());
-        assert_eq!(
-            default,
-            serde_json::from_str(r#"{"publishDecorations":null, "lruCapacity":null}"#).unwrap()
-        );
+    pub fn update_caps(&mut self, caps: &TextDocumentClientCapabilities) {
+        if let Some(value) = caps.definition.as_ref().and_then(|it| it.link_support) {
+            self.client_caps.location_link = value;
+        }
+        if let Some(value) = caps.folding_range.as_ref().and_then(|it| it.line_folding_only) {
+            self.client_caps.line_folding_only = value
+        }
     }
 }
diff --git a/crates/rust-analyzer/src/conv.rs b/crates/rust-analyzer/src/conv.rs
index 6edc03fe0..57c4c8ce5 100644
--- a/crates/rust-analyzer/src/conv.rs
+++ b/crates/rust-analyzer/src/conv.rs
@@ -579,7 +579,7 @@ impl TryConvWith<&WorldSnapshot> for (FileId, RangeInfo<Vec<NavigationTarget>>)
             .into_iter()
             .map(|nav| (file_id, RangeInfo::new(range, nav)))
             .try_conv_with_to_vec(world)?;
-        if world.options.supports_location_link {
+        if world.config.client_caps.location_link {
             Ok(links.into())
         } else {
             let locations: Vec<Location> = links
diff --git a/crates/rust-analyzer/src/feature_flags.rs b/crates/rust-analyzer/src/feature_flags.rs
deleted file mode 100644
index dbb3f50a0..000000000
--- a/crates/rust-analyzer/src/feature_flags.rs
+++ /dev/null
@@ -1,77 +0,0 @@
-//! See docs for `FeatureFlags`.
-
-use rustc_hash::FxHashMap;
-
-// FIXME: looks like a much better design is to pass options to each call,
-// rather than to have a global ambient feature flags -- that way, the clients
-// can issue two successive calls with different options.
-
-/// Feature flags hold fine-grained toggles for all *user-visible* features of
-/// rust-analyzer.
-///
-/// The exists such that users are able to disable any annoying feature (and,
-/// with many users and many features,  some features are bound to be annoying
-/// for some users)
-///
-/// Note that we purposefully use run-time checked strings, and not something
-/// checked at compile time, to keep things simple and flexible.
-///
-/// Also note that, at the moment, `FeatureFlags` also store features for
-/// `rust-analyzer`. This should be benign layering violation.
-#[derive(Debug)]
-pub struct FeatureFlags {
-    flags: FxHashMap<String, bool>,
-}
-
-impl FeatureFlags {
-    fn new(flags: &[(&str, bool)]) -> FeatureFlags {
-        let flags = flags
-            .iter()
-            .map(|&(name, value)| {
-                check_flag_name(name);
-                (name.to_string(), value)
-            })
-            .collect();
-        FeatureFlags { flags }
-    }
-
-    pub fn set(&mut self, flag: &str, value: bool) -> Result<(), ()> {
-        match self.flags.get_mut(flag) {
-            None => Err(()),
-            Some(slot) => {
-                *slot = value;
-                Ok(())
-            }
-        }
-    }
-
-    pub fn get(&self, flag: &str) -> bool {
-        match self.flags.get(flag) {
-            None => panic!("unknown flag: {:?}", flag),
-            Some(value) => *value,
-        }
-    }
-}
-
-impl Default for FeatureFlags {
-    fn default() -> FeatureFlags {
-        FeatureFlags::new(&[
-            ("lsp.diagnostics", true),
-            ("completion.insertion.add-call-parenthesis", true),
-            ("completion.insertion.add-argument-snippets", true),
-            ("completion.enable-postfix", true),
-            ("call-info.full", true),
-            ("notifications.workspace-loaded", true),
-            ("notifications.cargo-toml-not-found", true),
-        ])
-    }
-}
-
-fn check_flag_name(flag: &str) {
-    for c in flag.bytes() {
-        match c {
-            b'a'..=b'z' | b'-' | b'.' => (),
-            _ => panic!("flag name does not match conventions: {:?}", flag),
-        }
-    }
-}
diff --git a/crates/rust-analyzer/src/lib.rs b/crates/rust-analyzer/src/lib.rs
index e50e47b19..02953be30 100644
--- a/crates/rust-analyzer/src/lib.rs
+++ b/crates/rust-analyzer/src/lib.rs
@@ -33,18 +33,16 @@ mod conv;
 mod main_loop;
 mod markdown;
 pub mod req;
-mod config;
+pub mod config;
 mod world;
 mod diagnostics;
 mod semantic_tokens;
-mod feature_flags;
 
 use serde::de::DeserializeOwned;
 
 pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;
 pub use crate::{
     caps::server_capabilities,
-    config::ServerConfig,
     main_loop::LspError,
     main_loop::{main_loop, show_message},
 };
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 7825b0077..8d1429196 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -14,15 +14,16 @@ use std::{
     time::{Duration, Instant},
 };
 
-use crossbeam_channel::{select, unbounded, RecvError, Sender};
+use crossbeam_channel::{never, select, unbounded, RecvError, Sender};
 use lsp_server::{Connection, ErrorCode, Message, Notification, Request, RequestId, Response};
 use lsp_types::{
-    ClientCapabilities, NumberOrString, WorkDoneProgress, WorkDoneProgressBegin,
-    WorkDoneProgressCreateParams, WorkDoneProgressEnd, WorkDoneProgressReport,
+    NumberOrString, WorkDoneProgress, WorkDoneProgressBegin, WorkDoneProgressCreateParams,
+    WorkDoneProgressEnd, WorkDoneProgressReport,
 };
-use ra_cargo_watch::{url_from_path_with_drive_lowercasing, CheckOptions, CheckTask};
-use ra_ide::{Canceled, FileId, InlayHintsOptions, LibraryData, SourceRootId};
+use ra_flycheck::{url_from_path_with_drive_lowercasing, CheckTask};
+use ra_ide::{Canceled, FileId, LibraryData, SourceRootId};
 use ra_prof::profile;
+use ra_project_model::{PackageRoot, ProjectWorkspace};
 use ra_vfs::{VfsFile, VfsTask, Watch};
 use relative_path::RelativePathBuf;
 use rustc_hash::FxHashSet;
@@ -30,15 +31,15 @@ use serde::{de::DeserializeOwned, Serialize};
 use threadpool::ThreadPool;
 
 use crate::{
+    config::{Config, FilesWatcher},
     diagnostics::DiagnosticTask,
-    feature_flags::FeatureFlags,
     main_loop::{
         pending_requests::{PendingRequest, PendingRequests},
         subscriptions::Subscriptions,
     },
     req,
-    world::{Options, WorldSnapshot, WorldState},
-    Result, ServerConfig,
+    world::{WorldSnapshot, WorldState},
+    Result,
 };
 
 #[derive(Debug)]
@@ -63,13 +64,8 @@ impl fmt::Display for LspError {
 
 impl Error for LspError {}
 
-pub fn main_loop(
-    ws_roots: Vec<PathBuf>,
-    client_caps: ClientCapabilities,
-    config: ServerConfig,
-    connection: Connection,
-) -> Result<()> {
-    log::info!("server_config: {:#?}", config);
+pub fn main_loop(ws_roots: Vec<PathBuf>, config: Config, connection: Connection) -> Result<()> {
+    log::info!("initial config: {:#?}", config);
 
     // Windows scheduler implements priority boosts: if thread waits for an
     // event (like a condvar), and event fires, priority of the thread is
@@ -92,22 +88,6 @@ pub fn main_loop(
 
     let mut loop_state = LoopState::default();
     let mut world_state = {
-        let feature_flags = {
-            let mut ff = FeatureFlags::default();
-            for (flag, value) in config.feature_flags {
-                if ff.set(flag.as_str(), value).is_err() {
-                    log::error!("unknown feature flag: {:?}", flag);
-                    show_message(
-                        req::MessageType::Error,
-                        format!("unknown feature flag: {:?}", flag),
-                        &connection.sender,
-                    );
-                }
-            }
-            ff
-        };
-        log::info!("feature_flags: {:#?}", feature_flags);
-
         // FIXME: support dynamic workspace loading.
         let workspaces = {
             let mut loaded_workspaces = Vec::new();
@@ -115,7 +95,7 @@ pub fn main_loop(
                 let workspace = ra_project_model::ProjectWorkspace::discover_with_sysroot(
                     ws_root.as_path(),
                     config.with_sysroot,
-                    &config.cargo_features,
+                    &config.cargo,
                 );
                 match workspace {
                     Ok(workspace) => loaded_workspaces.push(workspace),
@@ -125,7 +105,7 @@ pub fn main_loop(
                         if let Some(ra_project_model::CargoTomlNotFoundError { .. }) =
                             e.downcast_ref()
                         {
-                            if !feature_flags.get("notifications.cargo-toml-not-found") {
+                            if !config.notifications.cargo_toml_not_found {
                                 continue;
                             }
                         }
@@ -142,17 +122,18 @@ pub fn main_loop(
         };
 
         let globs = config
-            .exclude_globs
+            .files
+            .exclude
             .iter()
             .map(|glob| crate::vfs_glob::Glob::new(glob))
             .collect::<std::result::Result<Vec<_>, _>>()?;
 
-        if config.use_client_watching {
+        if let FilesWatcher::Client = config.files.watcher {
             let registration_options = req::DidChangeWatchedFilesRegistrationOptions {
                 watchers: workspaces
                     .iter()
-                    .flat_map(|ws| ws.to_roots())
-                    .filter(|root| root.is_member())
+                    .flat_map(ProjectWorkspace::to_roots)
+                    .filter(PackageRoot::is_member)
                     .map(|root| format!("{}/**/*.rs", root.path().display()))
                     .map(|glob_pattern| req::FileSystemWatcher { glob_pattern, kind: None })
                     .collect(),
@@ -168,46 +149,19 @@ pub fn main_loop(
             connection.sender.send(request.into()).unwrap();
         }
 
-        let options = {
-            let text_document_caps = client_caps.text_document.as_ref();
-            Options {
-                publish_decorations: config.publish_decorations,
-                supports_location_link: text_document_caps
-                    .and_then(|it| it.definition)
-                    .and_then(|it| it.link_support)
-                    .unwrap_or(false),
-                line_folding_only: text_document_caps
-                    .and_then(|it| it.folding_range.as_ref())
-                    .and_then(|it| it.line_folding_only)
-                    .unwrap_or(false),
-                inlay_hints: InlayHintsOptions {
-                    type_hints: config.inlay_hints_type,
-                    parameter_hints: config.inlay_hints_parameter,
-                    chaining_hints: config.inlay_hints_chaining,
-                    max_length: config.inlay_hints_max_length,
-                },
-                cargo_watch: CheckOptions {
-                    enable: config.cargo_watch_enable,
-                    args: config.cargo_watch_args,
-                    command: config.cargo_watch_command,
-                    all_targets: config.cargo_watch_all_targets,
-                },
-                rustfmt_args: config.rustfmt_args,
-                vscode_lldb: config.vscode_lldb,
-            }
-        };
-
         WorldState::new(
             ws_roots,
             workspaces,
             config.lru_capacity,
             &globs,
-            Watch(!config.use_client_watching),
-            options,
-            feature_flags,
+            Watch(matches!(config.files.watcher, FilesWatcher::Notify)),
+            config,
         )
     };
 
+    loop_state.roots_total = world_state.vfs.read().n_roots();
+    loop_state.roots_scanned = 0;
+
     let pool = ThreadPool::default();
     let (task_sender, task_receiver) = unbounded::<Task>();
     let (libdata_sender, libdata_receiver) = unbounded::<LibraryData>();
@@ -229,7 +183,7 @@ pub fn main_loop(
                     Err(RecvError) => return Err("vfs died".into()),
                 },
                 recv(libdata_receiver) -> data => Event::Lib(data.unwrap()),
-                recv(world_state.check_watcher.task_recv) -> task => match task {
+                recv(world_state.flycheck.as_ref().map_or(&never(), |it| &it.task_recv)) -> task => match task {
                     Ok(task) => Event::CheckWatcher(task),
                     Err(RecvError) => return Err("check watcher died".into()),
                 }
@@ -297,9 +251,7 @@ impl fmt::Debug for Event {
                 }
             }
             Event::Task(Task::Notify(not)) => {
-                if notification_is::<req::PublishDecorations>(not)
-                    || notification_is::<req::PublishDiagnostics>(not)
-                {
+                if notification_is::<req::PublishDiagnostics>(not) {
                     return debug_verbose_not(not, f);
                 }
             }
@@ -333,7 +285,10 @@ struct LoopState {
     in_flight_libraries: usize,
     pending_libraries: Vec<(SourceRootId, Vec<(FileId, RelativePathBuf, Arc<String>)>)>,
     workspace_loaded: bool,
-    roots_scanned_progress: Option<usize>,
+    roots_progress_reported: Option<usize>,
+    roots_scanned: usize,
+    roots_total: usize,
+    configuration_request_id: Option<RequestId>,
 }
 
 impl LoopState {
@@ -377,6 +332,7 @@ fn loop_turn(
             world_state.add_lib(lib);
             world_state.maybe_collect_garbage();
             loop_state.in_flight_libraries -= 1;
+            loop_state.roots_scanned += 1;
         }
         Event::CheckWatcher(task) => on_check_task(task, world_state, task_sender)?,
         Event::Msg(msg) => match msg {
@@ -390,25 +346,41 @@ fn loop_turn(
                 req,
             )?,
             Message::Notification(not) => {
-                on_notification(
-                    &connection.sender,
-                    world_state,
-                    &mut loop_state.pending_requests,
-                    &mut loop_state.subscriptions,
-                    not,
-                )?;
+                on_notification(&connection.sender, world_state, loop_state, not)?;
             }
             Message::Response(resp) => {
                 let removed = loop_state.pending_responses.remove(&resp.id);
                 if !removed {
                     log::error!("unexpected response: {:?}", resp)
                 }
+
+                if Some(&resp.id) == loop_state.configuration_request_id.as_ref() {
+                    loop_state.configuration_request_id = None;
+                    log::debug!("config update response: '{:?}", resp);
+                    let Response { error, result, .. } = resp;
+
+                    match (error, result) {
+                        (Some(err), _) => {
+                            log::error!("failed to fetch the server settings: {:?}", err)
+                        }
+                        (None, Some(configs)) => {
+                            if let Some(new_config) = configs.get(0) {
+                                let mut config = world_state.config.clone();
+                                config.update(&new_config);
+                                world_state.update_configuration(config);
+                            }
+                        }
+                        (None, None) => {
+                            log::error!("received empty server settings response from the client")
+                        }
+                    }
+                }
             }
         },
     };
 
     let mut state_changed = false;
-    if let Some(changes) = world_state.process_changes() {
+    if let Some(changes) = world_state.process_changes(&mut loop_state.roots_scanned) {
         state_changed = true;
         loop_state.pending_libraries.extend(changes);
     }
@@ -427,28 +399,33 @@ fn loop_turn(
         });
     }
 
+    let show_progress =
+        !loop_state.workspace_loaded && world_state.config.notifications.workspace_loaded;
+
     if !loop_state.workspace_loaded
-        && world_state.roots_to_scan == 0
+        && loop_state.roots_scanned == loop_state.roots_total
         && loop_state.pending_libraries.is_empty()
         && loop_state.in_flight_libraries == 0
     {
         loop_state.workspace_loaded = true;
-        world_state.check_watcher.update();
+        if let Some(flycheck) = &world_state.flycheck {
+            flycheck.update();
+        }
         pool.execute({
             let subs = loop_state.subscriptions.subscriptions();
             let snap = world_state.snapshot();
             move || snap.analysis().prime_caches(subs).unwrap_or_else(|_: Canceled| ())
         });
-        send_startup_progress(&connection.sender, loop_state, world_state);
-    } else if !loop_state.workspace_loaded {
-        send_startup_progress(&connection.sender, loop_state, world_state);
+    }
+
+    if show_progress {
+        send_startup_progress(&connection.sender, loop_state);
     }
 
     if state_changed {
         update_file_notifications_on_threadpool(
             pool,
             world_state.snapshot(),
-            world_state.options.publish_decorations,
             task_sender.clone(),
             loop_state.subscriptions.subscriptions(),
         )
@@ -529,7 +506,6 @@ fn on_request(
         .on::<req::GotoTypeDefinition>(handlers::handle_goto_type_definition)?
         .on::<req::ParentModule>(handlers::handle_parent_module)?
         .on::<req::Runnables>(handlers::handle_runnables)?
-        .on::<req::DecorationsRequest>(handlers::handle_decorations)?
         .on::<req::Completion>(handlers::handle_completion)?
         .on::<req::CodeActionRequest>(handlers::handle_code_action)?
         .on::<req::CodeLensRequest>(handlers::handle_code_lens)?
@@ -556,8 +532,7 @@ fn on_request(
 fn on_notification(
     msg_sender: &Sender<Message>,
     state: &mut WorldState,
-    pending_requests: &mut PendingRequests,
-    subs: &mut Subscriptions,
+    loop_state: &mut LoopState,
     not: Notification,
 ) -> Result<()> {
     let not = match notification_cast::<req::Cancel>(not) {
@@ -566,7 +541,7 @@ fn on_notification(
                 NumberOrString::Number(id) => id.into(),
                 NumberOrString::String(id) => id.into(),
             };
-            if pending_requests.cancel(&id) {
+            if loop_state.pending_requests.cancel(&id) {
                 let response = Response::new_err(
                     id,
                     ErrorCode::RequestCanceled as i32,
@@ -585,7 +560,7 @@ fn on_notification(
             if let Some(file_id) =
                 state.vfs.write().add_file_overlay(&path, params.text_document.text)
             {
-                subs.add_sub(FileId(file_id.0));
+                loop_state.subscriptions.add_sub(FileId(file_id.0));
             }
             return Ok(());
         }
@@ -604,7 +579,9 @@ fn on_notification(
     };
     let not = match notification_cast::<req::DidSaveTextDocument>(not) {
         Ok(_params) => {
-            state.check_watcher.update();
+            if let Some(flycheck) = &state.flycheck {
+                flycheck.update();
+            }
             return Ok(());
         }
         Err(not) => not,
@@ -614,7 +591,7 @@ fn on_notification(
             let uri = params.text_document.uri;
             let path = uri.to_file_path().map_err(|()| format!("invalid uri: {}", uri))?;
             if let Some(file_id) = state.vfs.write().remove_file_overlay(path.as_path()) {
-                subs.remove_sub(FileId(file_id.0));
+                loop_state.subscriptions.remove_sub(FileId(file_id.0));
             }
             let params =
                 req::PublishDiagnosticsParams { uri, diagnostics: Vec::new(), version: None };
@@ -625,7 +602,22 @@ fn on_notification(
         Err(not) => not,
     };
     let not = match notification_cast::<req::DidChangeConfiguration>(not) {
-        Ok(_params) => {
+        Ok(_) => {
+            // As stated in https://github.com/microsoft/language-server-protocol/issues/676,
+            // this notification's parameters should be ignored and the actual config queried separately.
+            let request_id = loop_state.next_request_id();
+            let request = request_new::<req::WorkspaceConfiguration>(
+                request_id.clone(),
+                req::ConfigurationParams {
+                    items: vec![req::ConfigurationItem {
+                        scope_uri: None,
+                        section: Some("rust-analyzer".to_string()),
+                    }],
+                },
+            );
+            msg_sender.send(request.into())?;
+            loop_state.configuration_request_id = Some(request_id);
+
             return Ok(());
         }
         Err(not) => not,
@@ -706,21 +698,13 @@ fn on_diagnostic_task(task: DiagnosticTask, msg_sender: &Sender<Message>, state:
     }
 }
 
-fn send_startup_progress(
-    sender: &Sender<Message>,
-    loop_state: &mut LoopState,
-    world_state: &WorldState,
-) {
-    if !world_state.feature_flags.get("notifications.workspace-loaded") {
-        return;
-    }
-
-    let total: usize = world_state.workspaces.iter().map(|it| it.n_packages()).sum();
-    let prev_progress = loop_state.roots_scanned_progress;
-    let progress = total - world_state.roots_to_scan;
-    loop_state.roots_scanned_progress = Some(progress);
+fn send_startup_progress(sender: &Sender<Message>, loop_state: &mut LoopState) {
+    let total: usize = loop_state.roots_total;
+    let prev = loop_state.roots_progress_reported;
+    let progress = loop_state.roots_scanned;
+    loop_state.roots_progress_reported = Some(progress);
 
-    match (prev_progress, loop_state.workspace_loaded) {
+    match (prev, loop_state.workspace_loaded) {
         (None, false) => {
             let work_done_progress_create = request_new::<req::WorkDoneProgressCreate>(
                 loop_state.next_request_id(),
@@ -755,14 +739,14 @@ fn send_startup_progress(
         ),
         _ => {}
     }
-}
 
-fn send_startup_progress_notif(sender: &Sender<Message>, work_done_progress: WorkDoneProgress) {
-    let notif = notification_new::<req::Progress>(req::ProgressParams {
-        token: req::ProgressToken::String("rustAnalyzer/startup".into()),
-        value: req::ProgressParamsValue::WorkDone(work_done_progress),
-    });
-    sender.send(notif.into()).unwrap();
+    fn send_startup_progress_notif(sender: &Sender<Message>, work_done_progress: WorkDoneProgress) {
+        let notif = notification_new::<req::Progress>(req::ProgressParams {
+            token: req::ProgressToken::String("rustAnalyzer/startup".into()),
+            value: req::ProgressParamsValue::WorkDone(work_done_progress),
+        });
+        sender.send(notif.into()).unwrap();
+    }
 }
 
 struct PoolDispatcher<'a> {
@@ -902,15 +886,13 @@ where
 fn update_file_notifications_on_threadpool(
     pool: &ThreadPool,
     world: WorldSnapshot,
-    publish_decorations: bool,
     task_sender: Sender<Task>,
     subscriptions: Vec<FileId>,
 ) {
     log::trace!("updating notifications for {:?}", subscriptions);
-    let publish_diagnostics = world.feature_flags.get("lsp.diagnostics");
-    pool.execute(move || {
-        for file_id in subscriptions {
-            if publish_diagnostics {
+    if world.config.publish_diagnostics {
+        pool.execute(move || {
+            for file_id in subscriptions {
                 match handlers::publish_diagnostics(&world, file_id) {
                     Err(e) => {
                         if !is_canceled(&e) {
@@ -922,21 +904,8 @@ fn update_file_notifications_on_threadpool(
                     }
                 }
             }
-            if publish_decorations {
-                match handlers::publish_decorations(&world, file_id) {
-                    Err(e) => {
-                        if !is_canceled(&e) {
-                            log::error!("failed to compute decorations: {:?}", e);
-                        }
-                    }
-                    Ok(params) => {
-                        let not = notification_new::<req::PublishDecorations>(params);
-                        task_sender.send(Task::Notify(not)).unwrap();
-                    }
-                }
-            }
-        }
-    });
+        })
+    }
 }
 
 pub fn show_message(typ: req::MessageType, message: impl Into<String>, sender: &Sender<Message>) {
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index 12f8ca297..b207f0764 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -14,13 +14,13 @@ use lsp_types::{
     CodeAction, CodeActionResponse, CodeLens, Command, CompletionItem, Diagnostic,
     DocumentFormattingParams, DocumentHighlight, DocumentSymbol, FoldingRange, FoldingRangeParams,
     Hover, HoverContents, Location, MarkupContent, MarkupKind, Position, PrepareRenameResponse,
-    Range, RenameParams, SemanticTokens, SemanticTokensParams, SemanticTokensRangeParams,
+    Range, RenameParams, SemanticTokensParams, SemanticTokensRangeParams,
     SemanticTokensRangeResult, SemanticTokensResult, SymbolInformation, TextDocumentIdentifier,
     TextEdit, WorkspaceEdit,
 };
 use ra_ide::{
-    Assist, AssistId, CompletionOptions, FileId, FilePosition, FileRange, Query, RangeInfo,
-    Runnable, RunnableKind, SearchScope,
+    Assist, AssistId, FileId, FilePosition, FileRange, Query, RangeInfo, Runnable, RunnableKind,
+    SearchScope,
 };
 use ra_prof::profile;
 use ra_syntax::{AstNode, SyntaxKind, TextRange, TextUnit};
@@ -31,13 +31,14 @@ use stdx::format_to;
 
 use crate::{
     cargo_target_spec::CargoTargetSpec,
+    config::RustfmtConfig,
     conv::{
         to_call_hierarchy_item, to_location, Conv, ConvWith, FoldConvCtx, MapConvWith, TryConvWith,
         TryConvWithToVec,
     },
     diagnostics::DiagnosticTask,
     from_json,
-    req::{self, Decoration, InlayHint, InlayHintsParams},
+    req::{self, InlayHint, InlayHintsParams},
     semantic_tokens::SemanticTokensBuilder,
     world::WorldSnapshot,
     LspError, Result,
@@ -388,15 +389,6 @@ pub fn handle_runnables(
     Ok(res)
 }
 
-pub fn handle_decorations(
-    world: WorldSnapshot,
-    params: TextDocumentIdentifier,
-) -> Result<Vec<Decoration>> {
-    let _p = profile("handle_decorations");
-    let file_id = params.try_conv_with(&world)?;
-    highlight(&world, file_id)
-}
-
 pub fn handle_completion(
     world: WorldSnapshot,
     params: req::CompletionParams,
@@ -425,15 +417,7 @@ pub fn handle_completion(
         return Ok(None);
     }
 
-    let options = CompletionOptions {
-        enable_postfix_completions: world.feature_flags.get("completion.enable-postfix"),
-        add_call_parenthesis: world.feature_flags.get("completion.insertion.add-call-parenthesis"),
-        add_call_argument_snippets: world
-            .feature_flags
-            .get("completion.insertion.add-argument-snippets"),
-    };
-
-    let items = match world.analysis().completions(position, &options)? {
+    let items = match world.analysis().completions(position, &world.config.completion)? {
         None => return Ok(None),
         Some(items) => items,
     };
@@ -457,7 +441,7 @@ pub fn handle_folding_range(
     let ctx = FoldConvCtx {
         text: &text,
         line_index: &line_index,
-        line_folding_only: world.options.line_folding_only,
+        line_folding_only: world.config.client_caps.line_folding_only,
     };
     let res = Some(folds.into_iter().map_conv_with(&ctx).collect());
     Ok(res)
@@ -470,7 +454,7 @@ pub fn handle_signature_help(
     let _p = profile("handle_signature_help");
     let position = params.try_conv_with(&world)?;
     if let Some(call_info) = world.analysis().call_info(position)? {
-        let concise = !world.feature_flags.get("call-info.full");
+        let concise = !world.config.call_info_full;
         let mut active_parameter = call_info.active_parameter.map(|it| it as i64);
         if concise && call_info.signature.has_self_param {
             active_parameter = active_parameter.map(|it| it.saturating_sub(1));
@@ -610,13 +594,24 @@ pub fn handle_formatting(
     let file_line_index = world.analysis().file_line_index(file_id)?;
     let end_position = TextUnit::of_str(&file).conv_with(&file_line_index);
 
-    let mut rustfmt = process::Command::new("rustfmt");
-    rustfmt.args(&world.options.rustfmt_args);
-    if let Some(&crate_id) = crate_ids.first() {
-        // Assume all crates are in the same edition
-        let edition = world.analysis().crate_edition(crate_id)?;
-        rustfmt.args(&["--edition", &edition.to_string()]);
-    }
+    let mut rustfmt = match &world.config.rustfmt {
+        RustfmtConfig::Rustfmt { extra_args } => {
+            let mut cmd = process::Command::new("rustfmt");
+            cmd.args(extra_args);
+            if let Some(&crate_id) = crate_ids.first() {
+                // Assume all crates are in the same edition
+                let edition = world.analysis().crate_edition(crate_id)?;
+                cmd.arg("--edition");
+                cmd.arg(edition.to_string());
+            }
+            cmd
+        }
+        RustfmtConfig::CustomCommand { command, args } => {
+            let mut cmd = process::Command::new(command);
+            cmd.args(args);
+            cmd
+        }
+    };
 
     if let Ok(path) = params.text_document.uri.to_file_path() {
         if let Some(parent) = path.parent() {
@@ -815,23 +810,21 @@ pub fn handle_code_lens(
         };
         lenses.push(lens);
 
-        if world.options.vscode_lldb {
-            if r.args[0] == "run" {
-                r.args[0] = "build".into();
-            } else {
-                r.args.push("--no-run".into());
-            }
-            let debug_lens = CodeLens {
-                range: r.range,
-                command: Some(Command {
-                    title: "Debug".into(),
-                    command: "rust-analyzer.debugSingle".into(),
-                    arguments: Some(vec![to_value(r).unwrap()]),
-                }),
-                data: None,
-            };
-            lenses.push(debug_lens);
+        if r.args[0] == "run" {
+            r.args[0] = "build".into();
+        } else {
+            r.args.push("--no-run".into());
         }
+        let debug_lens = CodeLens {
+            range: r.range,
+            command: Some(Command {
+                title: "Debug".into(),
+                command: "rust-analyzer.debugSingle".into(),
+                arguments: Some(vec![to_value(r).unwrap()]),
+            }),
+            data: None,
+        };
+        lenses.push(debug_lens);
     }
 
     // Handle impls
@@ -966,15 +959,6 @@ pub fn publish_diagnostics(world: &WorldSnapshot, file_id: FileId) -> Result<Dia
     Ok(DiagnosticTask::SetNative(file_id, diagnostics))
 }
 
-pub fn publish_decorations(
-    world: &WorldSnapshot,
-    file_id: FileId,
-) -> Result<req::PublishDecorationsParams> {
-    let _p = profile("publish_decorations");
-    let uri = world.file_id_to_uri(file_id)?;
-    Ok(req::PublishDecorationsParams { uri, decorations: highlight(&world, file_id)? })
-}
-
 fn to_lsp_runnable(
     world: &WorldSnapshot,
     file_id: FileId,
@@ -1004,21 +988,6 @@ fn to_lsp_runnable(
     })
 }
 
-fn highlight(world: &WorldSnapshot, file_id: FileId) -> Result<Vec<Decoration>> {
-    let line_index = world.analysis().file_line_index(file_id)?;
-    let res = world
-        .analysis()
-        .highlight(file_id)?
-        .into_iter()
-        .map(|h| Decoration {
-            range: h.range.conv_with(&line_index),
-            tag: h.highlight.to_string(),
-            binding_hash: h.binding_hash.map(|x| x.to_string()),
-        })
-        .collect();
-    Ok(res)
-}
-
 pub fn handle_inlay_hints(
     world: WorldSnapshot,
     params: InlayHintsParams,
@@ -1028,7 +997,7 @@ pub fn handle_inlay_hints(
     let analysis = world.analysis();
     let line_index = analysis.file_line_index(file_id)?;
     Ok(analysis
-        .inlay_hints(file_id, &world.options.inlay_hints)?
+        .inlay_hints(file_id, &world.config.inlay_hints)?
         .into_iter()
         .map_conv_with(&line_index)
         .collect())
@@ -1145,7 +1114,7 @@ pub fn handle_semantic_tokens(
         }
     }
 
-    let tokens = SemanticTokens { data: builder.build(), ..Default::default() };
+    let tokens = builder.build();
 
     Ok(Some(tokens.into()))
 }
@@ -1166,7 +1135,7 @@ pub fn handle_semantic_tokens_range(
         builder.push(highlight_range.range.conv_with(&line_index), token_type, token_modifiers);
     }
 
-    let tokens = SemanticTokens { data: builder.build(), ..Default::default() };
+    let tokens = builder.build();
 
     Ok(Some(tokens.into()))
 }
diff --git a/crates/rust-analyzer/src/main_loop/subscriptions.rs b/crates/rust-analyzer/src/main_loop/subscriptions.rs
index bee6437cf..2c76418be 100644
--- a/crates/rust-analyzer/src/main_loop/subscriptions.rs
+++ b/crates/rust-analyzer/src/main_loop/subscriptions.rs
@@ -17,6 +17,6 @@ impl Subscriptions {
         self.subs.remove(&file_id);
     }
     pub(crate) fn subscriptions(&self) -> Vec<FileId> {
-        self.subs.iter().cloned().collect()
+        self.subs.iter().copied().collect()
     }
 }
diff --git a/crates/rust-analyzer/src/req.rs b/crates/rust-analyzer/src/req.rs
index 8557294f6..b8b627e28 100644
--- a/crates/rust-analyzer/src/req.rs
+++ b/crates/rust-analyzer/src/req.rs
@@ -1,13 +1,13 @@
 //! Defines `rust-analyzer` specific custom messages.
 
-use lsp_types::{Location, Position, Range, TextDocumentIdentifier, Url};
+use lsp_types::{Location, Position, Range, TextDocumentIdentifier};
 use rustc_hash::FxHashMap;
 use serde::{Deserialize, Serialize};
 
 pub use lsp_types::{
     notification::*, request::*, ApplyWorkspaceEditParams, CodeActionParams, CodeLens,
-    CodeLensParams, CompletionParams, CompletionResponse, DiagnosticTag,
-    DidChangeConfigurationParams, DidChangeWatchedFilesParams,
+    CodeLensParams, CompletionParams, CompletionResponse, ConfigurationItem, ConfigurationParams,
+    DiagnosticTag, DidChangeConfigurationParams, DidChangeWatchedFilesParams,
     DidChangeWatchedFilesRegistrationOptions, DocumentOnTypeFormattingParams, DocumentSymbolParams,
     DocumentSymbolResponse, FileSystemWatcher, Hover, InitializeResult, MessageType,
     PartialResultParams, ProgressParams, ProgressParamsValue, ProgressToken,
@@ -86,36 +86,6 @@ pub struct FindMatchingBraceParams {
     pub offsets: Vec<Position>,
 }
 
-pub enum DecorationsRequest {}
-
-impl Request for DecorationsRequest {
-    type Params = TextDocumentIdentifier;
-    type Result = Vec<Decoration>;
-    const METHOD: &'static str = "rust-analyzer/decorationsRequest";
-}
-
-pub enum PublishDecorations {}
-
-impl Notification for PublishDecorations {
-    type Params = PublishDecorationsParams;
-    const METHOD: &'static str = "rust-analyzer/publishDecorations";
-}
-
-#[derive(Deserialize, Serialize, Debug)]
-#[serde(rename_all = "camelCase")]
-pub struct PublishDecorationsParams {
-    pub uri: Url,
-    pub decorations: Vec<Decoration>,
-}
-
-#[derive(Deserialize, Serialize, Debug)]
-#[serde(rename_all = "camelCase")]
-pub struct Decoration {
-    pub range: Range,
-    pub tag: String,
-    pub binding_hash: Option<String>,
-}
-
 pub enum ParentModule {}
 
 impl Request for ParentModule {
diff --git a/crates/rust-analyzer/src/semantic_tokens.rs b/crates/rust-analyzer/src/semantic_tokens.rs
index d9ba77050..2a66bbfd8 100644
--- a/crates/rust-analyzer/src/semantic_tokens.rs
+++ b/crates/rust-analyzer/src/semantic_tokens.rs
@@ -2,7 +2,7 @@
 
 use std::ops;
 
-use lsp_types::{Range, SemanticToken, SemanticTokenModifier, SemanticTokenType};
+use lsp_types::{Range, SemanticToken, SemanticTokenModifier, SemanticTokenType, SemanticTokens};
 
 pub(crate) const ATTRIBUTE: SemanticTokenType = SemanticTokenType::new("attribute");
 pub(crate) const BUILTIN_TYPE: SemanticTokenType = SemanticTokenType::new("builtinType");
@@ -109,8 +109,8 @@ impl SemanticTokensBuilder {
         self.prev_char = range.start.character as u32;
     }
 
-    pub fn build(self) -> Vec<SemanticToken> {
-        self.data
+    pub fn build(self) -> SemanticTokens {
+        SemanticTokens { result_id: None, data: self.data }
     }
 }
 
diff --git a/crates/rust-analyzer/src/vfs_glob.rs b/crates/rust-analyzer/src/vfs_glob.rs
index 91b33f94e..ff37a7008 100644
--- a/crates/rust-analyzer/src/vfs_glob.rs
+++ b/crates/rust-analyzer/src/vfs_glob.rs
@@ -29,10 +29,14 @@ impl RustPackageFilterBuilder {
         self.is_member = is_member;
         self
     }
-    pub fn exclude(mut self, glob: Glob) -> RustPackageFilterBuilder {
-        self.exclude.add(glob);
+
+    pub fn exclude(mut self, globs: impl IntoIterator<Item = Glob>) -> RustPackageFilterBuilder {
+        for glob in globs.into_iter() {
+            self.exclude.add(glob);
+        }
         self
     }
+
     pub fn into_vfs_filter(self) -> Box<dyn Filter> {
         let RustPackageFilterBuilder { is_member, mut exclude } = self;
         for &glob in ALWAYS_IGNORED {
@@ -87,7 +91,7 @@ fn test_globs() {
 
     let filter = RustPackageFilterBuilder::default()
         .set_member(true)
-        .exclude(Glob::new("src/llvm-project/**").unwrap())
+        .exclude(std::iter::once(Glob::new("src/llvm-project/**").unwrap()))
         .into_vfs_filter();
 
     assert!(!filter.include_dir(RelativePath::new("src/llvm-project/clang")));
diff --git a/crates/rust-analyzer/src/world.rs b/crates/rust-analyzer/src/world.rs
index 64a7b907e..365f57d8c 100644
--- a/crates/rust-analyzer/src/world.rs
+++ b/crates/rust-analyzer/src/world.rs
@@ -11,10 +11,9 @@ use std::{
 use crossbeam_channel::{unbounded, Receiver};
 use lsp_types::Url;
 use parking_lot::RwLock;
-use ra_cargo_watch::{url_from_path_with_drive_lowercasing, CheckOptions, CheckWatcher};
+use ra_flycheck::{url_from_path_with_drive_lowercasing, Flycheck, FlycheckConfig};
 use ra_ide::{
-    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, InlayHintsOptions, LibraryData,
-    SourceRootId,
+    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData, SourceRootId,
 };
 use ra_project_model::{get_rustc_cfg_options, ProcMacroClient, ProjectWorkspace};
 use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsRoot, VfsTask, Watch};
@@ -22,8 +21,8 @@ use relative_path::RelativePathBuf;
 use stdx::format_to;
 
 use crate::{
+    config::Config,
     diagnostics::{CheckFixes, DiagnosticCollection},
-    feature_flags::FeatureFlags,
     main_loop::pending_requests::{CompletedRequest, LatestRequests},
     vfs_glob::{Glob, RustPackageFilterBuilder},
     LspError, Result,
@@ -31,15 +30,22 @@ use crate::{
 use ra_db::ExternSourceId;
 use rustc_hash::{FxHashMap, FxHashSet};
 
-#[derive(Debug, Clone)]
-pub struct Options {
-    pub publish_decorations: bool,
-    pub supports_location_link: bool,
-    pub line_folding_only: bool,
-    pub inlay_hints: InlayHintsOptions,
-    pub rustfmt_args: Vec<String>,
-    pub cargo_watch: CheckOptions,
-    pub vscode_lldb: bool,
+fn create_flycheck(workspaces: &[ProjectWorkspace], config: &FlycheckConfig) -> Option<Flycheck> {
+    // FIXME: Figure out the multi-workspace situation
+    workspaces
+        .iter()
+        .find_map(|w| match w {
+            ProjectWorkspace::Cargo { cargo, .. } => Some(cargo),
+            ProjectWorkspace::Json { .. } => None,
+        })
+        .map(|cargo| {
+            let cargo_project_root = cargo.workspace_root().to_path_buf();
+            Some(Flycheck::new(config.clone(), cargo_project_root))
+        })
+        .unwrap_or_else(|| {
+            log::warn!("Cargo check watching only supported for cargo workspaces, disabling");
+            None
+        })
 }
 
 /// `WorldState` is the primary mutable state of the language server
@@ -49,24 +55,20 @@ pub struct Options {
 /// incremental salsa database.
 #[derive(Debug)]
 pub struct WorldState {
-    pub options: Options,
-    pub feature_flags: Arc<FeatureFlags>,
-    //FIXME: this belongs to `LoopState` rather than to `WorldState`
-    pub roots_to_scan: usize,
+    pub config: Config,
     pub roots: Vec<PathBuf>,
     pub workspaces: Arc<Vec<ProjectWorkspace>>,
     pub analysis_host: AnalysisHost,
     pub vfs: Arc<RwLock<Vfs>>,
     pub task_receiver: Receiver<VfsTask>,
     pub latest_requests: Arc<RwLock<LatestRequests>>,
-    pub check_watcher: CheckWatcher,
+    pub flycheck: Option<Flycheck>,
     pub diagnostics: DiagnosticCollection,
 }
 
 /// An immutable snapshot of the world's state at a point in time.
 pub struct WorldSnapshot {
-    pub options: Options,
-    pub feature_flags: Arc<FeatureFlags>,
+    pub config: Config,
     pub workspaces: Arc<Vec<ProjectWorkspace>>,
     pub analysis: Analysis,
     pub latest_requests: Arc<RwLock<LatestRequests>>,
@@ -81,49 +83,39 @@ impl WorldState {
         lru_capacity: Option<usize>,
         exclude_globs: &[Glob],
         watch: Watch,
-        options: Options,
-        feature_flags: FeatureFlags,
+        config: Config,
     ) -> WorldState {
         let mut change = AnalysisChange::new();
 
-        let mut roots = Vec::new();
-        roots.extend(folder_roots.iter().map(|path| {
-            let mut filter = RustPackageFilterBuilder::default().set_member(true);
-            for glob in exclude_globs.iter() {
-                filter = filter.exclude(glob.clone());
-            }
-            RootEntry::new(path.clone(), filter.into_vfs_filter())
-        }));
-        for ws in workspaces.iter() {
-            roots.extend(ws.to_roots().into_iter().map(|pkg_root| {
-                let mut filter =
-                    RustPackageFilterBuilder::default().set_member(pkg_root.is_member());
-                for glob in exclude_globs.iter() {
-                    filter = filter.exclude(glob.clone());
-                }
-                RootEntry::new(pkg_root.path().clone(), filter.into_vfs_filter())
-            }));
-        }
-
-        let mut extern_dirs = FxHashSet::default();
-        for ws in workspaces.iter() {
-            extern_dirs.extend(ws.out_dirs());
-        }
-
-        let mut extern_source_roots = FxHashMap::default();
-
-        roots.extend(extern_dirs.iter().map(|path| {
-            let mut filter = RustPackageFilterBuilder::default().set_member(false);
-            for glob in exclude_globs.iter() {
-                filter = filter.exclude(glob.clone());
-            }
-            RootEntry::new(PathBuf::from(&path), filter.into_vfs_filter())
-        }));
+        let extern_dirs: FxHashSet<_> =
+            workspaces.iter().flat_map(ProjectWorkspace::out_dirs).collect();
+
+        let roots: Vec<_> = {
+            let create_filter = |is_member| {
+                RustPackageFilterBuilder::default()
+                    .set_member(is_member)
+                    .exclude(exclude_globs.iter().cloned())
+                    .into_vfs_filter()
+            };
+            folder_roots
+                .iter()
+                .map(|path| RootEntry::new(path.clone(), create_filter(true)))
+                .chain(workspaces.iter().flat_map(ProjectWorkspace::to_roots).map(|pkg_root| {
+                    RootEntry::new(pkg_root.path().to_owned(), create_filter(pkg_root.is_member()))
+                }))
+                .chain(
+                    extern_dirs
+                        .iter()
+                        .map(|path| RootEntry::new(path.to_owned(), create_filter(false))),
+                )
+                .collect()
+        };
 
         let (task_sender, task_receiver) = unbounded();
         let task_sender = Box::new(move |t| task_sender.send(t).unwrap());
         let (mut vfs, vfs_roots) = Vfs::new(roots, task_sender, watch);
-        let roots_to_scan = vfs_roots.len();
+
+        let mut extern_source_roots = FxHashMap::default();
         for r in vfs_roots {
             let vfs_root_path = vfs.root2path(r);
             let is_local = folder_roots.iter().any(|it| vfs_root_path.starts_with(it));
@@ -151,8 +143,23 @@ impl WorldState {
             vfs_file.map(|f| FileId(f.0))
         };
 
-        let proc_macro_client =
-            ProcMacroClient::extern_process(std::path::Path::new("ra_proc_macro_srv"));
+        let proc_macro_client = match &config.proc_macro_srv {
+            None => ProcMacroClient::dummy(),
+            Some(srv) => {
+                let path = Path::new(&srv);
+                match ProcMacroClient::extern_process(path) {
+                    Ok(it) => it,
+                    Err(err) => {
+                        log::error!(
+                            "Fail to run ra_proc_macro_srv from path {}, error : {}",
+                            path.to_string_lossy(),
+                            err
+                        );
+                        ProcMacroClient::dummy()
+                    }
+                }
+            }
+        };
 
         workspaces
             .iter()
@@ -169,43 +176,38 @@ impl WorldState {
             });
         change.set_crate_graph(crate_graph);
 
-        // FIXME: Figure out the multi-workspace situation
-        let check_watcher = workspaces
-            .iter()
-            .find_map(|w| match w {
-                ProjectWorkspace::Cargo { cargo, .. } => Some(cargo),
-                ProjectWorkspace::Json { .. } => None,
-            })
-            .map(|cargo| {
-                let cargo_project_root = cargo.workspace_root().to_path_buf();
-                CheckWatcher::new(&options.cargo_watch, cargo_project_root)
-            })
-            .unwrap_or_else(|| {
-                log::warn!("Cargo check watching only supported for cargo workspaces, disabling");
-                CheckWatcher::dummy()
-            });
+        let flycheck = config.check.as_ref().and_then(|c| create_flycheck(&workspaces, c));
 
         let mut analysis_host = AnalysisHost::new(lru_capacity);
         analysis_host.apply_change(change);
         WorldState {
-            options,
-            feature_flags: Arc::new(feature_flags),
-            roots_to_scan,
+            config: config,
             roots: folder_roots,
             workspaces: Arc::new(workspaces),
             analysis_host,
             vfs: Arc::new(RwLock::new(vfs)),
             task_receiver,
             latest_requests: Default::default(),
-            check_watcher,
+            flycheck,
             diagnostics: Default::default(),
         }
     }
 
+    pub fn update_configuration(&mut self, config: Config) {
+        self.analysis_host.update_lru_capacity(config.lru_capacity);
+        if config.check != self.config.check {
+            self.flycheck =
+                config.check.as_ref().and_then(|it| create_flycheck(&self.workspaces, it));
+        }
+
+        self.config = config;
+    }
+
     /// Returns a vec of libraries
     /// FIXME: better API here
     pub fn process_changes(
         &mut self,
+        roots_scanned: &mut usize,
     ) -> Option<Vec<(SourceRootId, Vec<(FileId, RelativePathBuf, Arc<String>)>)>> {
         let changes = self.vfs.write().commit_changes();
         if changes.is_empty() {
@@ -219,7 +221,7 @@ impl WorldState {
                     let root_path = self.vfs.read().root2path(root);
                     let is_local = self.roots.iter().any(|r| root_path.starts_with(r));
                     if is_local {
-                        self.roots_to_scan -= 1;
+                        *roots_scanned += 1;
                         for (file, path, text) in files {
                             change.add_file(SourceRootId(root.0), FileId(file.0), path, text);
                         }
@@ -247,7 +249,6 @@ impl WorldState {
     }
 
     pub fn add_lib(&mut self, data: LibraryData) {
-        self.roots_to_scan -= 1;
         let mut change = AnalysisChange::new();
         change.add_library(data);
         self.analysis_host.apply_change(change);
@@ -255,8 +256,7 @@ impl WorldState {
 
     pub fn snapshot(&self) -> WorldSnapshot {
         WorldSnapshot {
-            options: self.options.clone(),
-            feature_flags: Arc::clone(&self.feature_flags),
+            config: self.config.clone(),
             workspaces: Arc::clone(&self.workspaces),
             analysis: self.analysis_host.analysis(),
             vfs: Arc::clone(&self.vfs),
diff --git a/crates/rust-analyzer/tests/heavy_tests/main.rs b/crates/rust-analyzer/tests/heavy_tests/main.rs
index 145429571..638813311 100644
--- a/crates/rust-analyzer/tests/heavy_tests/main.rs
+++ b/crates/rust-analyzer/tests/heavy_tests/main.rs
@@ -9,7 +9,7 @@ use lsp_types::{
 };
 use rust_analyzer::req::{
     CodeActionParams, CodeActionRequest, Completion, CompletionParams, DidOpenTextDocument,
-    Formatting, OnEnter, Runnables, RunnablesParams,
+    Formatting, GotoDefinition, OnEnter, Runnables, RunnablesParams,
 };
 use serde_json::json;
 use tempfile::TempDir;
@@ -581,3 +581,47 @@ version = \"0.0.0\"
         }),
     );
 }
+
+#[test]
+fn resolve_include_concat_env() {
+    if skip_slow_tests() {
+        return;
+    }
+
+    let server = Project::with_fixture(
+        r###"
+//- Cargo.toml
+[package]
+name = "foo"
+version = "0.0.0"
+
+//- build.rs
+use std::{env, fs, path::Path};
+
+fn main() {
+    let out_dir = env::var_os("OUT_DIR").unwrap();
+    let dest_path = Path::new(&out_dir).join("hello.rs");
+    fs::write(
+        &dest_path,
+        r#"pub fn message() -> &'static str { "Hello, World!" }"#,
+    )
+    .unwrap();
+    println!("cargo:rerun-if-changed=build.rs");
+}
+//- src/main.rs
+include!(concat!(env!("OUT_DIR"), "/hello.rs"));
+
+fn main() { message(); }
+"###,
+    )
+    .with_config(|config| {
+        config.cargo.load_out_dirs_from_check = true;
+    })
+    .server();
+    server.wait_until_workspace_is_loaded();
+    let res = server.send_request::<GotoDefinition>(TextDocumentPositionParams::new(
+        server.doc_id("src/main.rs"),
+        Position::new(2, 15),
+    ));
+    assert!(format!("{}", res).contains("hello.rs"));
+}
diff --git a/crates/rust-analyzer/tests/heavy_tests/support.rs b/crates/rust-analyzer/tests/heavy_tests/support.rs
index 1d7062bdf..7eebedff7 100644
--- a/crates/rust-analyzer/tests/heavy_tests/support.rs
+++ b/crates/rust-analyzer/tests/heavy_tests/support.rs
@@ -11,8 +11,7 @@ use lsp_server::{Connection, Message, Notification, Request};
 use lsp_types::{
     notification::{DidOpenTextDocument, Exit},
     request::Shutdown,
-    ClientCapabilities, DidOpenTextDocumentParams, GotoCapability, TextDocumentClientCapabilities,
-    TextDocumentIdentifier, TextDocumentItem, Url, WorkDoneProgress,
+    DidOpenTextDocumentParams, TextDocumentIdentifier, TextDocumentItem, Url, WorkDoneProgress,
 };
 use serde::Serialize;
 use serde_json::{to_string_pretty, Value};
@@ -20,18 +19,22 @@ use tempfile::TempDir;
 use test_utils::{find_mismatch, parse_fixture};
 
 use req::{ProgressParams, ProgressParamsValue};
-use rust_analyzer::{main_loop, req, ServerConfig};
+use rust_analyzer::{
+    config::{ClientCapsConfig, Config},
+    main_loop, req,
+};
 
 pub struct Project<'a> {
     fixture: &'a str,
     with_sysroot: bool,
     tmp_dir: Option<TempDir>,
     roots: Vec<PathBuf>,
+    config: Option<Box<dyn Fn(&mut Config)>>,
 }
 
 impl<'a> Project<'a> {
     pub fn with_fixture(fixture: &str) -> Project {
-        Project { fixture, tmp_dir: None, roots: vec![], with_sysroot: false }
+        Project { fixture, tmp_dir: None, roots: vec![], with_sysroot: false, config: None }
     }
 
     pub fn tmp_dir(mut self, tmp_dir: TempDir) -> Project<'a> {
@@ -49,6 +52,11 @@ impl<'a> Project<'a> {
         self
     }
 
+    pub fn with_config(mut self, config: impl Fn(&mut Config) + 'static) -> Project<'a> {
+        self.config = Some(Box::new(config));
+        self
+    }
+
     pub fn server(self) -> Server {
         let tmp_dir = self.tmp_dir.unwrap_or_else(|| TempDir::new().unwrap());
         static INIT: Once = Once::new();
@@ -72,7 +80,17 @@ impl<'a> Project<'a> {
 
         let roots = self.roots.into_iter().map(|root| tmp_dir.path().join(root)).collect();
 
-        Server::new(tmp_dir, self.with_sysroot, roots, paths)
+        let mut config = Config {
+            client_caps: ClientCapsConfig { location_link: true, ..Default::default() },
+            with_sysroot: self.with_sysroot,
+            ..Config::default()
+        };
+
+        if let Some(f) = &self.config {
+            f(&mut config)
+        }
+
+        Server::new(tmp_dir, config, roots, paths)
     }
 }
 
@@ -83,15 +101,16 @@ pub fn project(fixture: &str) -> Server {
 pub struct Server {
     req_id: Cell<u64>,
     messages: RefCell<Vec<Message>>,
-    dir: TempDir,
     _thread: jod_thread::JoinHandle<()>,
     client: Connection,
+    /// XXX: remove the tempdir last
+    dir: TempDir,
 }
 
 impl Server {
     fn new(
         dir: TempDir,
-        with_sysroot: bool,
+        config: Config,
         roots: Vec<PathBuf>,
         files: Vec<(PathBuf, String)>,
     ) -> Server {
@@ -102,26 +121,7 @@ impl Server {
 
         let _thread = jod_thread::Builder::new()
             .name("test server".to_string())
-            .spawn(move || {
-                main_loop(
-                    roots,
-                    ClientCapabilities {
-                        workspace: None,
-                        text_document: Some(TextDocumentClientCapabilities {
-                            definition: Some(GotoCapability {
-                                dynamic_registration: None,
-                                link_support: Some(true),
-                            }),
-                            ..Default::default()
-                        }),
-                        window: None,
-                        experimental: None,
-                    },
-                    ServerConfig { with_sysroot, ..ServerConfig::default() },
-                    connection,
-                )
-                .unwrap()
-            })
+            .spawn(move || main_loop(roots, config, connection).unwrap())
             .expect("failed to spawn a thread");
 
         let res =
@@ -187,6 +187,7 @@ impl Server {
         self.client.sender.send(r.into()).unwrap();
         while let Some(msg) = self.recv() {
             match msg {
+                Message::Request(req) if req.method == "window/workDoneProgress/create" => (),
                 Message::Request(req) => panic!("unexpected request: {:?}", req),
                 Message::Notification(_) => (),
                 Message::Response(res) => {
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index 8492c17af..d2efa2236 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -5,7 +5,7 @@ use std::{cell::Cell, fmt};
 /// Appends formatted string to a `String`.
 #[macro_export]
 macro_rules! format_to {
-    (&buf:expr) => ();
+    ($buf:expr) => ();
     ($buf:expr, $lit:literal $($arg:tt)*) => {
         { use ::std::fmt::Write as _; let _ = ::std::write!($buf, $lit $($arg)*); }
     };