24 files changed, 210 insertions, 127 deletions

diff --git a/.vscode/launch.json b/.vscode/launch.json
index 8ca27d878..021b8f048 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -120,6 +120,12 @@
       "sourceMaps": true,
       "outFiles": [ "${workspaceFolder}/editors/code/out/tests/unit/**/*.js" ],
       "preLaunchTask": "Pretest"
+    },
+    {
+      "name": "Win Attach to Server",
+      "type": "cppvsdbg",
+      "processId":"${command:pickProcess}",
+      "request": "attach"
     }
   ]
 }
diff --git a/Cargo.lock b/Cargo.lock
index efd1c6d33..fabe69285 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -16,6 +16,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ee2a4ec343196209d6594e19543ae87a39f96d5534d7174822a3ad825dd6ed7e"
 
 [[package]]
+name = "always-assert"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "727786f78c5bc0cda8011831616589f72084cb16b7df4213a997b78749b55a60"
+dependencies = [
+ "log",
+]
+
+[[package]]
 name = "ansi_term"
 version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -175,9 +184,9 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "chalk-derive"
-version = "0.50.0"
+version = "0.51.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ac605cf409013573e971d7292d4bec6f5495b19d5f98fc9d8b1a12270c3888e0"
+checksum = "f1a2ad10b964771ffc53ce7a8d6fce4bde3da0da82a1bc7a72668548db1c56ee"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -187,9 +196,9 @@ dependencies = [
 
 [[package]]
 name = "chalk-ir"
-version = "0.50.0"
+version = "0.51.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa1dbfb3c2c8b67edb5cd981f720550e43579090574f786145731f90c5d401ff"
+checksum = "17b14b40a09687aa5f0973721841d83a8a0e12a6b3ada1d2e01f0a694bb800ee"
 dependencies = [
  "bitflags",
  "chalk-derive",
@@ -198,9 +207,9 @@ dependencies = [
 
 [[package]]
 name = "chalk-recursive"
-version = "0.50.0"
+version = "0.51.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0882e2a3ba66901717a64f8bb0655e809f800ac6abed05cb605e7a41d4bf8999"
+checksum = "1c7297bb1683f63a4b334b53cfdd81a721e8adde3441514e1126d24aaafe2552"
 dependencies = [
  "chalk-derive",
  "chalk-ir",
@@ -211,9 +220,9 @@ dependencies = [
 
 [[package]]
 name = "chalk-solve"
-version = "0.50.0"
+version = "0.51.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d43cce07150eac39771ff4b198537cefef744734b2218a89c682295b54cd8d0"
+checksum = "82765c1a19e801d53fc9d145449701ddf79f394e6519f1e9c01fca1ee95d0ba7"
 dependencies = [
  "chalk-derive",
  "chalk-ir",
@@ -275,9 +284,9 @@ checksum = "28b9d6de7f49e22cf97ad17fc4036ece69300032f45f78f30b4a4482cdc3f4a6"
 
 [[package]]
 name = "countme"
-version = "2.0.0"
+version = "2.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4f8038ded86523aa26c1321dfe8bb432707d0a3e2608f9d0108803727546e089"
+checksum = "be0bdf97802dfc074a4cf9a1f087f7f8d6478ee039a46eba1644690bcc854d61"
 dependencies = [
  "dashmap",
  "once_cell",
@@ -878,11 +887,11 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.13"
+version = "0.4.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fcf3805d4480bb5b86070dcfeb9e2cb2ebc148adb753c5cca5f884d1d65a42b2"
+checksum = "51b9bbe6c47d51fc3e1a9b945965946b4c44142ab8792c50835a980d362c2710"
 dependencies = [
- "cfg-if 0.1.10",
+ "cfg-if 1.0.0",
 ]
 
 [[package]]
@@ -1415,6 +1424,7 @@ dependencies = [
 name = "rust-analyzer"
 version = "0.0.0"
 dependencies = [
+ "always-assert",
  "anyhow",
  "cfg",
  "crossbeam-channel 0.5.0",
@@ -1464,9 +1474,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-rustc_lexer"
-version = "700.0.0"
+version = "701.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ed36784376b69c941d7aa36e960a52ac712e2663960357121a4d9f2cc58e225"
+checksum = "3601c20fc378d11e965fb1f670cf8bad1ef5164fe4ec8cbb7c57fa9d656f2541"
 dependencies = [
  "unicode-xid",
 ]
@@ -1560,18 +1570,18 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.120"
+version = "1.0.123"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "166b2349061381baf54a58e4b13c89369feb0ef2eaa57198899e2312aac30aab"
+checksum = "92d5161132722baa40d802cc70b15262b98258453e85e5d1d365c757c73869ae"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.120"
+version = "1.0.123"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0ca2a8cb5805ce9e3b95435e3765b7b553cecc762d938d409434338386cb5775"
+checksum = "9391c295d64fc0abb2c556bad848f33cb8296276b1ad2677d1ae1ace4f258f31"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1658,14 +1668,15 @@ dependencies = [
 name = "stdx"
 version = "0.0.0"
 dependencies = [
+ "always-assert",
  "backtrace",
 ]
 
 [[package]]
 name = "syn"
-version = "1.0.59"
+version = "1.0.60"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "07cb8b1b4ebf86a89ee88cbd201b022b94138c623644d035185c84d3f41b7e66"
+checksum = "c700597eca8a5a762beb35753ef6b94df201c81cca676604f547495a0d7f0081"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1742,9 +1753,9 @@ dependencies = [
 
 [[package]]
 name = "thread_local"
-version = "1.1.1"
+version = "1.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "301bdd13d23c49672926be451130892d274d3ba0b410c18e00daa7990ff38d99"
+checksum = "d8208a331e1cb318dd5bd76951d2b8fc48ca38a69f5f4e4af1b6a9f8c6236915"
 dependencies = [
  "once_cell",
 ]
@@ -1771,9 +1782,9 @@ dependencies = [
 
 [[package]]
 name = "tinyvec"
-version = "1.1.0"
+version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ccf8dbc19eb42fba10e8feaaec282fb50e2c14b2726d6301dbfeed0f73306a6f"
+checksum = "317cca572a0e89c3ce0ca1f1bdc9369547fe318a683418e42ac8f59d14701023"
 dependencies = [
  "tinyvec_macros",
 ]
diff --git a/crates/assists/src/handlers/fill_match_arms.rs b/crates/assists/src/handlers/fill_match_arms.rs
index 7663d211d..4964ddc7d 100644
--- a/crates/assists/src/handlers/fill_match_arms.rs
+++ b/crates/assists/src/handlers/fill_match_arms.rs
@@ -272,6 +272,34 @@ mod tests {
     }
 
     #[test]
+    fn partial_fill_option() {
+        check_assist(
+            fill_match_arms,
+            r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+
+fn main() {
+    match None$0 {
+        None => {}
+    }
+}
+            "#,
+            r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+
+fn main() {
+    match None {
+        None => {}
+        Some(${0:_}) => {}
+    }
+}
+            "#,
+        );
+    }
+
+    #[test]
     fn partial_fill_or_pat() {
         check_assist(
             fill_match_arms,
diff --git a/crates/completion/src/item.rs b/crates/completion/src/item.rs
index eeb952ec3..8ec4ac65e 100644
--- a/crates/completion/src/item.rs
+++ b/crates/completion/src/item.rs
@@ -10,7 +10,7 @@ use ide_db::{
     },
     SymbolKind,
 };
-use stdx::{assert_never, impl_from};
+use stdx::{impl_from, never};
 use syntax::{algo, TextRange};
 use text_edit::TextEdit;
 
@@ -404,7 +404,7 @@ impl Builder {
     pub(crate) fn set_detail(mut self, detail: Option<impl Into<String>>) -> Builder {
         self.detail = detail.map(Into::into);
         if let Some(detail) = &self.detail {
-            if assert_never!(detail.contains('\n'), "multiline detail:\n{}", detail) {
+            if never!(detail.contains('\n'), "multiline detail:\n{}", detail) {
                 self.detail = Some(detail.splitn(2, '\n').next().unwrap().to_string());
             }
         }
diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index d0c84ab0b..b9ecf22fa 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -17,6 +17,7 @@ use hir_expand::{
     HirFileId, InFile, MacroDefId,
 };
 use la_arena::{Arena, ArenaMap};
+use profile::Count;
 use rustc_hash::FxHashMap;
 use syntax::{ast, AstNode, AstPtr};
 use test_utils::mark;
@@ -237,6 +238,7 @@ pub struct Body {
     /// The `ExprId` of the actual body expression.
     pub body_expr: ExprId,
     pub item_scope: ItemScope,
+    _c: Count<Self>,
 }
 
 pub type ExprPtr = AstPtr<ast::Expr>;
diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 4ce5e5b72..209965fca 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -10,6 +10,7 @@ use hir_expand::{
     ExpandError, HirFileId, MacroDefId, MacroDefKind,
 };
 use la_arena::Arena;
+use profile::Count;
 use rustc_hash::FxHashMap;
 use syntax::{
     ast::{
@@ -77,6 +78,7 @@ pub(super) fn lower(
             params: Vec::new(),
             body_expr: dummy_expr_id(),
             item_scope: Default::default(),
+            _c: Count::new(),
         },
         item_trees: {
             let mut map = FxHashMap::default();
diff --git a/crates/hir_expand/src/ast_id_map.rs b/crates/hir_expand/src/ast_id_map.rs
index 0991fffd8..16cf29907 100644
--- a/crates/hir_expand/src/ast_id_map.rs
+++ b/crates/hir_expand/src/ast_id_map.rs
@@ -13,6 +13,7 @@ use std::{
 };
 
 use la_arena::{Arena, Idx};
+use profile::Count;
 use syntax::{ast, match_ast, AstNode, AstPtr, SyntaxNode, SyntaxNodePtr};
 
 /// `AstId` points to an AST node in a specific file.
@@ -62,12 +63,13 @@ type ErasedFileAstId = Idx<SyntaxNodePtr>;
 #[derive(Debug, PartialEq, Eq, Default)]
 pub struct AstIdMap {
     arena: Arena<SyntaxNodePtr>,
+    _c: Count<Self>,
 }
 
 impl AstIdMap {
     pub(crate) fn from_source(node: &SyntaxNode) -> AstIdMap {
         assert!(node.parent().is_none());
-        let mut res = AstIdMap { arena: Arena::default() };
+        let mut res = AstIdMap::default();
         // By walking the tree in breadth-first order we make sure that parents
         // get lower ids then children. That is, adding a new child does not
         // change parent's id. This means that, say, adding a new function to a
diff --git a/crates/hir_ty/Cargo.toml b/crates/hir_ty/Cargo.toml
index db42a00dc..c7502bf57 100644
--- a/crates/hir_ty/Cargo.toml
+++ b/crates/hir_ty/Cargo.toml
@@ -17,9 +17,9 @@ ena = "0.14.0"
 log = "0.4.8"
 rustc-hash = "1.1.0"
 scoped-tls = "1"
-chalk-solve = { version = "0.50", default-features = false }
-chalk-ir = "0.50"
-chalk-recursive = "0.50"
+chalk-solve = { version = "0.51", default-features = false }
+chalk-ir = "0.51"
+chalk-recursive = "0.51"
 la-arena = { version = "0.2.0", path = "../../lib/arena" }
 
 stdx = { path = "../stdx", version = "0.0.0" }
diff --git a/crates/ide/src/inlay_hints.rs b/crates/ide/src/inlay_hints.rs
index 54485fd30..2f37c8040 100644
--- a/crates/ide/src/inlay_hints.rs
+++ b/crates/ide/src/inlay_hints.rs
@@ -416,8 +416,11 @@ fn get_string_representation(expr: &ast::Expr) -> Option<String> {
                 name_ref => Some(name_ref.to_owned()),
             }
         }
+        ast::Expr::FieldExpr(field_expr) => Some(field_expr.name_ref()?.to_string()),
+        ast::Expr::PathExpr(path_expr) => Some(path_expr.to_string()),
+        ast::Expr::PrefixExpr(prefix_expr) => get_string_representation(&prefix_expr.expr()?),
         ast::Expr::RefExpr(ref_expr) => get_string_representation(&ref_expr.expr()?),
-        _ => Some(expr.to_string()),
+        _ => None,
     }
 }
 
@@ -1438,4 +1441,19 @@ fn main() {
 "#,
         )
     }
+
+    #[test]
+    fn param_name_hints_show_for_literals() {
+        check(
+            r#"pub fn test(a: i32, b: i32) -> [i32; 2] { [a, b] }
+fn main() {
+    test(
+        0x0fab272b,
+      //^^^^^^^^^^ a
+        0x0fab272b
+      //^^^^^^^^^^ b
+    );
+}"#,
+        )
+    }
 }
diff --git a/crates/ide/src/references/rename.rs b/crates/ide/src/references/rename.rs
index c25bcce50..99a558532 100644
--- a/crates/ide/src/references/rename.rs
+++ b/crates/ide/src/references/rename.rs
@@ -9,7 +9,7 @@ use ide_db::{
     search::FileReference,
     RootDatabase,
 };
-use stdx::assert_never;
+use stdx::never;
 use syntax::{
     ast::{self, NameOwner},
     lex_single_syntax_kind, AstNode, SyntaxKind, SyntaxNode, T,
@@ -285,7 +285,7 @@ fn rename_mod(
 }
 
 fn rename_to_self(sema: &Semantics<RootDatabase>, local: hir::Local) -> RenameResult<SourceChange> {
-    if assert_never!(local.is_self(sema.db)) {
+    if never!(local.is_self(sema.db)) {
         bail!("rename_to_self invoked on self");
     }
 
@@ -388,7 +388,7 @@ fn rename_self_to_param(
     let (file_id, self_param) = match local.source(sema.db) {
         InFile { file_id, value: Either::Right(self_param) } => (file_id, self_param),
         _ => {
-            assert_never!(true, "rename_self_to_param invoked on a non-self local");
+            never!(true, "rename_self_to_param invoked on a non-self local");
             bail!("rename_self_to_param invoked on a non-self local");
         }
     };
diff --git a/crates/ide_db/src/source_change.rs b/crates/ide_db/src/source_change.rs
index b1f87731b..f76bac151 100644
--- a/crates/ide_db/src/source_change.rs
+++ b/crates/ide_db/src/source_change.rs
@@ -10,7 +10,7 @@ use std::{
 
 use base_db::{AnchoredPathBuf, FileId};
 use rustc_hash::FxHashMap;
-use stdx::assert_never;
+use stdx::never;
 use text_edit::TextEdit;
 
 #[derive(Default, Debug, Clone)]
@@ -40,10 +40,7 @@ impl SourceChange {
     pub fn insert_source_edit(&mut self, file_id: FileId, edit: TextEdit) {
         match self.source_file_edits.entry(file_id) {
             Entry::Occupied(mut entry) => {
-                assert_never!(
-                    entry.get_mut().union(edit).is_err(),
-                    "overlapping edits for same file"
-                );
+                never!(entry.get_mut().union(edit).is_err(), "overlapping edits for same file");
             }
             Entry::Vacant(entry) => {
                 entry.insert(edit);
diff --git a/crates/profile/Cargo.toml b/crates/profile/Cargo.toml
index 4dd9acc98..486f9c164 100644
--- a/crates/profile/Cargo.toml
+++ b/crates/profile/Cargo.toml
@@ -14,7 +14,7 @@ once_cell = "1.3.1"
 cfg-if = "1"
 libc = "0.2.73"
 la-arena = { version = "0.2.0", path = "../../lib/arena" }
-countme = { version = "2.0.0", features = ["enable"] }
+countme = { version = "2.0.1", features = ["enable"] }
 jemalloc-ctl = { version = "0.3.3", optional = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
diff --git a/crates/project_model/src/build_data.rs b/crates/project_model/src/build_data.rs
index cf32995e0..3ff347e2c 100644
--- a/crates/project_model/src/build_data.rs
+++ b/crates/project_model/src/build_data.rs
@@ -175,7 +175,7 @@ fn is_dylib(path: &Path) -> bool {
 /// Should be synced with <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates>
 fn inject_cargo_env(package: &cargo_metadata::Package, env: &mut Vec<(String, String)>) {
     // FIXME: Missing variables:
-    // CARGO, CARGO_PKG_HOMEPAGE, CARGO_CRATE_NAME, CARGO_BIN_NAME, CARGO_BIN_EXE_<name>
+    // CARGO_PKG_HOMEPAGE, CARGO_CRATE_NAME, CARGO_BIN_NAME, CARGO_BIN_EXE_<name>
 
     let mut manifest_dir = package.manifest_path.clone();
     manifest_dir.pop();
@@ -183,6 +183,9 @@ fn inject_cargo_env(package: &cargo_metadata::Package, env: &mut Vec<(String, St
         env.push(("CARGO_MANIFEST_DIR".into(), cargo_manifest_dir.into()));
     }
 
+    // Not always right, but works for common cases.
+    env.push(("CARGO".into(), "cargo".into()));
+
     env.push(("CARGO_PKG_VERSION".into(), package.version.to_string()));
     env.push(("CARGO_PKG_VERSION_MAJOR".into(), package.version.major.to_string()));
     env.push(("CARGO_PKG_VERSION_MINOR".into(), package.version.minor.to_string()));
diff --git a/crates/rust-analyzer/Cargo.toml b/crates/rust-analyzer/Cargo.toml
index 268c00942..82ea76666 100644
--- a/crates/rust-analyzer/Cargo.toml
+++ b/crates/rust-analyzer/Cargo.toml
@@ -37,6 +37,7 @@ lsp-server = "0.5.0"
 tracing = "0.1"
 tracing-subscriber = { version = "0.2", default-features = false, features = ["env-filter", "registry"] }
 tracing-tree = { version = "0.1.4" }
+always-assert = "0.1"
 
 stdx = { path = "../stdx", version = "0.0.0" }
 flycheck = { path = "../flycheck", version = "0.0.0" }
@@ -72,3 +73,4 @@ tt = { path = "../tt" }
 
 [features]
 jemalloc = ["jemallocator", "profile/jemalloc"]
+force-always-assert = ["always-assert/force"]
diff --git a/crates/rust-analyzer/src/bin/args.rs b/crates/rust-analyzer/src/bin/args.rs
index 7d917946e..2a532361d 100644
--- a/crates/rust-analyzer/src/bin/args.rs
+++ b/crates/rust-analyzer/src/bin/args.rs
@@ -14,7 +14,10 @@ use vfs::AbsPathBuf;
 pub(crate) struct Args {
     pub(crate) verbosity: Verbosity,
     pub(crate) log_file: Option<PathBuf>,
+    pub(crate) no_buffering: bool,
     pub(crate) command: Command,
+    #[allow(unused)]
+    pub(crate) wait_dbg: bool,
 }
 
 pub(crate) enum Command {
@@ -47,11 +50,17 @@ FLAGS:
     -vv, --spammy
     -q,  --quiet      Set verbosity
 
-    --log-file <PATH> Log to the specified filed instead of stderr
+    --log-file <PATH> Log to the specified file instead of stderr
+    --no-log-buffering
+                      Flush log records to the file immediately
+
+    --wait-dbg        Wait until a debugger is attached to.
+                      The flag is valid for debug builds only
 
 ENVIRONMENTAL VARIABLES:
     RA_LOG            Set log filter in env_logger format
     RA_PROFILE        Enable hierarchical profiler
+    RA_WAIT_DBG       If set acts like a --wait-dbg flag
 
 COMMANDS:
 
@@ -114,6 +123,8 @@ impl Args {
                 verbosity: Verbosity::Normal,
                 log_file: None,
                 command: Command::Version,
+                no_buffering: false,
+                wait_dbg: false,
             });
         }
 
@@ -130,21 +141,41 @@ impl Args {
             (false, true, true) => bail!("Invalid flags: -q conflicts with -v"),
         };
         let log_file = matches.opt_value_from_str("--log-file")?;
+        let no_buffering = matches.contains("--no-log-buffering");
+        let wait_dbg = matches.contains("--wait-dbg");
 
         if matches.contains(["-h", "--help"]) {
             eprintln!("{}", HELP);
-            return Ok(Args { verbosity, log_file: None, command: Command::Help });
+            return Ok(Args {
+                verbosity,
+                log_file: None,
+                command: Command::Help,
+                no_buffering,
+                wait_dbg,
+            });
         }
 
         if matches.contains("--print-config-schema") {
-            return Ok(Args { verbosity, log_file, command: Command::PrintConfigSchema });
+            return Ok(Args {
+                verbosity,
+                log_file,
+                command: Command::PrintConfigSchema,
+                no_buffering,
+                wait_dbg,
+            });
         }
 
         let subcommand = match matches.subcommand()? {
             Some(it) => it,
             None => {
                 finish_args(matches)?;
-                return Ok(Args { verbosity, log_file, command: Command::RunServer });
+                return Ok(Args {
+                    verbosity,
+                    log_file,
+                    command: Command::RunServer,
+                    no_buffering,
+                    wait_dbg,
+                });
             }
         };
         let command = match subcommand.as_str() {
@@ -219,11 +250,17 @@ impl Args {
             },
             _ => {
                 eprintln!("{}", HELP);
-                return Ok(Args { verbosity, log_file: None, command: Command::Help });
+                return Ok(Args {
+                    verbosity,
+                    log_file: None,
+                    command: Command::Help,
+                    no_buffering,
+                    wait_dbg,
+                });
             }
         };
         finish_args(matches)?;
-        Ok(Args { verbosity, log_file, command })
+        Ok(Args { verbosity, log_file, command, no_buffering, wait_dbg })
     }
 }
 
diff --git a/crates/rust-analyzer/src/bin/logger.rs b/crates/rust-analyzer/src/bin/logger.rs
index 3bcb1ae37..14887c5cc 100644
--- a/crates/rust-analyzer/src/bin/logger.rs
+++ b/crates/rust-analyzer/src/bin/logger.rs
@@ -4,7 +4,7 @@
 
 use std::{
     fs::File,
-    io::{BufWriter, Write},
+    io::{self, BufWriter, Write},
 };
 
 use env_logger::filter::{Builder, Filter};
@@ -14,10 +14,11 @@ use parking_lot::Mutex;
 pub(crate) struct Logger {
     filter: Filter,
     file: Option<Mutex<BufWriter<File>>>,
+    no_buffering: bool,
 }
 
 impl Logger {
-    pub(crate) fn new(log_file: Option<File>, filter: Option<&str>) -> Logger {
+    pub(crate) fn new(log_file: Option<File>, no_buffering: bool, filter: Option<&str>) -> Logger {
         let filter = {
             let mut builder = Builder::new();
             if let Some(filter) = filter {
@@ -28,7 +29,7 @@ impl Logger {
 
         let file = log_file.map(|it| Mutex::new(BufWriter::new(it)));
 
-        Logger { filter, file }
+        Logger { filter, file, no_buffering }
     }
 
     pub(crate) fn install(self) {
@@ -46,7 +47,8 @@ impl Log for Logger {
         if !self.filter.matches(record) {
             return;
         }
-        match &self.file {
+
+        let should_flush = match &self.file {
             Some(w) => {
                 let _ = writeln!(
                     w.lock(),
@@ -55,19 +57,32 @@ impl Log for Logger {
                     record.module_path().unwrap_or_default(),
                     record.args(),
                 );
+                self.no_buffering
+            }
+            None => {
+                eprintln!(
+                    "[{} {}] {}",
+                    record.level(),
+                    record.module_path().unwrap_or_default(),
+                    record.args(),
+                );
+                true // flush stderr unconditionally
             }
-            None => eprintln!(
-                "[{} {}] {}",
-                record.level(),
-                record.module_path().unwrap_or_default(),
-                record.args(),
-            ),
+        };
+
+        if should_flush {
+            self.flush();
         }
     }
 
     fn flush(&self) {
-        if let Some(w) = &self.file {
-            let _ = w.lock().flush();
+        match &self.file {
+            Some(w) => {
+                let _ = w.lock().flush();
+            }
+            None => {
+                let _ = io::stderr().flush();
+            }
         }
     }
 }
diff --git a/crates/rust-analyzer/src/bin/main.rs b/crates/rust-analyzer/src/bin/main.rs
index 1d6e5478b..088b17b03 100644
--- a/crates/rust-analyzer/src/bin/main.rs
+++ b/crates/rust-analyzer/src/bin/main.rs
@@ -21,6 +21,7 @@ static ALLOC: jemallocator::Jemalloc = jemallocator::Jemalloc;
 
 fn main() {
     if let Err(err) = try_main() {
+        log::error!("Unexpected error: {}", err);
         eprintln!("{}", err);
         process::exit(101);
     }
@@ -28,7 +29,17 @@ fn main() {
 
 fn try_main() -> Result<()> {
     let args = args::Args::parse()?;
-    setup_logging(args.log_file)?;
+
+    #[cfg(debug_assertions)]
+    if args.wait_dbg || env::var("RA_WAIT_DBG").is_ok() {
+        #[allow(unused_mut)]
+        let mut d = 4;
+        while d == 4 {
+            d = 4;
+        }
+    }
+
+    setup_logging(args.log_file, args.no_buffering)?;
     match args.command {
         args::Command::RunServer => run_server()?,
         args::Command::PrintConfigSchema => {
@@ -56,7 +67,7 @@ fn try_main() -> Result<()> {
     Ok(())
 }
 
-fn setup_logging(log_file: Option<PathBuf>) -> Result<()> {
+fn setup_logging(log_file: Option<PathBuf>, no_buffering: bool) -> Result<()> {
     env::set_var("RUST_BACKTRACE", "short");
 
     let log_file = match log_file {
@@ -69,21 +80,12 @@ fn setup_logging(log_file: Option<PathBuf>) -> Result<()> {
         None => None,
     };
     let filter = env::var("RA_LOG").ok();
-    logger::Logger::new(log_file, filter.as_deref()).install();
+    logger::Logger::new(log_file, no_buffering, filter.as_deref()).install();
 
     tracing_setup::setup_tracing()?;
 
     profile::init();
 
-    if !cfg!(debug_assertions) {
-        stdx::set_assert_hook(|loc, args| {
-            if env::var("RA_PROFILE").is_ok() {
-                panic!("assertion failed at {}: {}", loc, args)
-            }
-            log::error!("assertion failed at {}: {}", loc, args)
-        });
-    }
-
     Ok(())
 }
 
diff --git a/crates/stdx/Cargo.toml b/crates/stdx/Cargo.toml
index c47e8d0a8..5866c0a28 100644
--- a/crates/stdx/Cargo.toml
+++ b/crates/stdx/Cargo.toml
@@ -11,6 +11,7 @@ doctest = false
 
 [dependencies]
 backtrace = { version = "0.3.44", optional = true }
+always-assert = { version = "0.1.1", features = ["log"] }
 # Think twice before adding anything here
 
 [features]
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index d42817078..d26be4853 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -4,7 +4,7 @@ use std::{cmp::Ordering, ops, process, time::Instant};
 mod macros;
 pub mod panic_context;
 
-pub use crate::macros::{on_assert_failure, set_assert_hook};
+pub use always_assert::{always, never};
 
 #[inline(always)]
 pub fn is_ci() -> bool {
diff --git a/crates/stdx/src/macros.rs b/crates/stdx/src/macros.rs
index 4f5c6100d..d91fc690c 100644
--- a/crates/stdx/src/macros.rs
+++ b/crates/stdx/src/macros.rs
@@ -1,9 +1,5 @@
 //! Convenience macros.
 
-use std::{
-    fmt, mem, panic,
-    sync::atomic::{AtomicUsize, Ordering::SeqCst},
-};
 #[macro_export]
 macro_rules! eprintln {
     ($($tt:tt)*) => {{
@@ -49,50 +45,3 @@ macro_rules! impl_from {
         )*
     }
 }
-
-/// A version of `assert!` macro which allows to handle an assertion failure.
-///
-/// In release mode, it returns the condition and logs an error.
-///
-/// ```
-/// if assert_never!(impossible) {
-///     // Heh, this shouldn't have happened, but lets try to soldier on...
-///     return None;
-/// }
-/// ```
-///
-/// Rust analyzer is a long-running process, and crashing really isn't an option.
-///
-/// Shamelessly stolen from: https://www.sqlite.org/assert.html
-#[macro_export]
-macro_rules! assert_never {
-    ($cond:expr) => { $crate::assert_never!($cond, "") };
-    ($cond:expr, $($fmt:tt)*) => {{
-        let value = $cond;
-        if value {
-            $crate::on_assert_failure(
-                format_args!($($fmt)*)
-            );
-        }
-        value
-    }};
-}
-
-type AssertHook = fn(&panic::Location<'_>, fmt::Arguments<'_>);
-static HOOK: AtomicUsize = AtomicUsize::new(0);
-
-pub fn set_assert_hook(hook: AssertHook) {
-    HOOK.store(hook as usize, SeqCst);
-}
-
-#[cold]
-#[track_caller]
-pub fn on_assert_failure(args: fmt::Arguments) {
-    let hook: usize = HOOK.load(SeqCst);
-    if hook == 0 {
-        panic!("\n  assertion failed: {}\n", args);
-    }
-
-    let hook: AssertHook = unsafe { mem::transmute::<usize, AssertHook>(hook) };
-    hook(panic::Location::caller(), args)
-}
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index e70fbba9c..de65585cb 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -13,7 +13,7 @@ doctest = false
 [dependencies]
 itertools = "0.10.0"
 rowan = "0.12.2"
-rustc_lexer = { version = "700.0.0", package = "rustc-ap-rustc_lexer" }
+rustc_lexer = { version = "701.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.5.1"
 once_cell = "1.3.1"
diff --git a/docs/dev/debugging.md b/docs/dev/debugging.md
index 8c48fd5a1..cc7a790ff 100644
--- a/docs/dev/debugging.md
+++ b/docs/dev/debugging.md
@@ -57,6 +57,14 @@ To apply changes to an already running debug process, press <kbd>Ctrl+Shift+P</k
 
 - Go back to the `[Extension Development Host]` instance and hover over a Rust variable and your breakpoint should hit.
 
+If you need to debug the server from the very beginning, including its initialization code, you can use the `--wait-dbg` command line argument or `RA_WAIT_DBG` environment variable. The server will spin at the beginning of the `try_main` function (see `crates\rust-analyzer\src\bin\main.rs`)
+```rust
+    let mut d = 4;
+    while d == 4 { // set a breakpoint here and change the value
+        d = 4;
+    }
+```
+
 ## Demo
 
 - [Debugging TypeScript VScode extension](https://www.youtube.com/watch?v=T-hvpK6s4wM).
diff --git a/docs/dev/style.md b/docs/dev/style.md
index 6dc6868c2..0c5e2ad33 100644
--- a/docs/dev/style.md
+++ b/docs/dev/style.md
@@ -232,7 +232,7 @@ if idx >= len {
 ## Assertions
 
 Assert liberally.
-Prefer `stdx::assert_never!` to standard `assert!`.
+Prefer `stdx::never!` to standard `assert!`.
 
 ## Getters & Setters
 
diff --git a/xtask/src/install.rs b/xtask/src/install.rs
index 202c74426..81b9956b8 100644
--- a/xtask/src/install.rs
+++ b/xtask/src/install.rs
@@ -180,7 +180,7 @@ fn install_server(opts: ServerOpt) -> Result<()> {
         Malloc::Jemalloc => &["--features", "jemalloc"],
     };
 
-    let cmd = cmd!("cargo install --path crates/rust-analyzer --locked --force {features...}");
+    let cmd = cmd!("cargo install --path crates/rust-analyzer --locked --force --features force-always-assert {features...}");
     let res = cmd.run();
 
     if res.is_err() && old_rust {