4 files changed, 58 insertions, 11 deletions

diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index c8d34e15a..728dc9962 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -122,6 +122,9 @@ impl GlobalState {
     }
 
     pub(crate) fn process_changes(&mut self) -> bool {
+        let mut fs_changes = Vec::new();
+        let mut has_fs_changes = false;
+
         let change = {
             let mut change = AnalysisChange::new();
             let (vfs, line_endings_map) = &mut *self.vfs.write();
@@ -130,13 +133,14 @@ impl GlobalState {
                 return false;
             }
 
-            let fs_op = changed_files.iter().any(|it| it.is_created_or_deleted());
-            if fs_op {
-                let roots = self.source_root_config.partition(&vfs);
-                change.set_roots(roots)
-            }
-
             for file in changed_files {
+                if file.is_created_or_deleted() {
+                    if let Some(path) = vfs.file_path(file.file_id).as_path() {
+                        fs_changes.push((path.to_path_buf(), file.change_kind));
+                        has_fs_changes = true;
+                    }
+                }
+
                 let text = if file.exists() {
                     let bytes = vfs.file_contents(file.file_id).to_vec();
                     match String::from_utf8(bytes).ok() {
@@ -152,10 +156,15 @@ impl GlobalState {
                 };
                 change.change_file(file.file_id, text);
             }
+            if has_fs_changes {
+                let roots = self.source_root_config.partition(&vfs);
+                change.set_roots(roots);
+            }
             change
         };
 
         self.analysis_host.apply_change(change);
+        self.maybe_refresh(&fs_changes);
         true
     }
 
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 96e2399ce..cea03fb6b 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -22,6 +22,7 @@ use crate::{
     Result,
 };
 use ra_project_model::ProjectWorkspace;
+use vfs::ChangeKind;
 
 pub fn main_loop(config: Config, connection: Connection) -> Result<()> {
     log::info!("initial config: {:#?}", config);
@@ -428,7 +429,9 @@ impl GlobalState {
                 if let Some(flycheck) = &this.flycheck {
                     flycheck.handle.update();
                 }
-                this.maybe_refresh(params.text_document.uri.as_str());
+                if let Ok(abs_path) = from_proto::abs_path(&params.text_document.uri) {
+                    this.maybe_refresh(&[(abs_path, ChangeKind::Modify)]);
+                }
                 Ok(())
             })?
             .on::<lsp_types::notification::DidChangeConfiguration>(|this, _params| {
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index 0a201fceb..a425320f6 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -6,7 +6,7 @@ use flycheck::FlycheckHandle;
 use ra_db::{CrateGraph, SourceRoot, VfsPath};
 use ra_ide::AnalysisChange;
 use ra_project_model::{PackageRoot, ProcMacroClient, ProjectWorkspace};
-use vfs::{file_set::FileSetConfig, AbsPath};
+use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
 
 use crate::{
     config::{Config, FilesWatcher, LinkedProject},
@@ -27,8 +27,8 @@ impl GlobalState {
             self.reload_flycheck();
         }
     }
-    pub(crate) fn maybe_refresh(&mut self, saved_doc_url: &str) {
-        if !(saved_doc_url.ends_with("Cargo.toml") || saved_doc_url.ends_with("Cargo.lock")) {
+    pub(crate) fn maybe_refresh(&mut self, changes: &[(AbsPathBuf, ChangeKind)]) {
+        if !changes.iter().any(|(path, kind)| is_interesting(path, *kind)) {
             return;
         }
         match self.status {
@@ -40,6 +40,41 @@ impl GlobalState {
         } else {
             self.transition(Status::NeedsReload);
         }
+
+        fn is_interesting(path: &AbsPath, change_kind: ChangeKind) -> bool {
+            const IMPLICIT_TARGET_FILES: &[&str] = &["build.rs", "src/main.rs", "src/lib.rs"];
+            const IMPLICIT_TARGET_DIRS: &[&str] = &["src/bin", "examples", "tests", "benches"];
+
+            if path.ends_with("Cargo.toml") || path.ends_with("Cargo.lock") {
+                return true;
+            }
+            if change_kind == ChangeKind::Modify {
+                return false;
+            }
+            if path.extension().map(|it| it.to_str()) != Some("rs".into()) {
+                return false;
+            }
+            if IMPLICIT_TARGET_FILES.iter().any(|it| path.ends_with(it)) {
+                return true;
+            }
+            let parent = match path.parent() {
+                Some(it) => it,
+                None => return false,
+            };
+            if IMPLICIT_TARGET_DIRS.iter().any(|it| parent.ends_with(it)) {
+                return true;
+            }
+            if path.ends_with("main.rs") {
+                let grand_parent = match parent.parent() {
+                    Some(it) => it,
+                    None => return false,
+                };
+                if IMPLICIT_TARGET_DIRS.iter().any(|it| grand_parent.ends_with(it)) {
+                    return true;
+                }
+            }
+            false
+        }
     }
     pub(crate) fn transition(&mut self, new_status: Status) {
         self.status = new_status;
diff --git a/crates/vfs/src/lib.rs b/crates/vfs/src/lib.rs
index 024e58018..569da8a1c 100644
--- a/crates/vfs/src/lib.rs
+++ b/crates/vfs/src/lib.rs
@@ -70,7 +70,7 @@ impl ChangedFile {
     }
 }
 
-#[derive(Eq, PartialEq)]
+#[derive(Eq, PartialEq, Copy, Clone)]
 pub enum ChangeKind {
     Create,
     Modify,