8 files changed, 384 insertions, 304 deletions

diff --git a/Cargo.lock b/Cargo.lock
index c902caeb4..382eb92e4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -126,9 +126,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "chalk-engine"
 version = "0.9.0"
-source = "git+https://github.com/rust-lang/chalk.git#13303bb0067c6ed0572322080ae367ee38f9e7c9"
+source = "git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9#13303bb0067c6ed0572322080ae367ee38f9e7c9"
 dependencies = [
- "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git)",
+ "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "stacker 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -136,17 +136,17 @@ dependencies = [
 [[package]]
 name = "chalk-ir"
 version = "0.1.0"
-source = "git+https://github.com/rust-lang/chalk.git#13303bb0067c6ed0572322080ae367ee38f9e7c9"
+source = "git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9#13303bb0067c6ed0572322080ae367ee38f9e7c9"
 dependencies = [
- "chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git)",
+ "chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
  "lalrpop-intern 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "chalk-macros"
 version = "0.1.1"
-source = "git+https://github.com/rust-lang/chalk.git#13303bb0067c6ed0572322080ae367ee38f9e7c9"
+source = "git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9#13303bb0067c6ed0572322080ae367ee38f9e7c9"
 dependencies = [
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -154,22 +154,22 @@ dependencies = [
 [[package]]
 name = "chalk-rust-ir"
 version = "0.1.0"
-source = "git+https://github.com/rust-lang/chalk.git#13303bb0067c6ed0572322080ae367ee38f9e7c9"
+source = "git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9#13303bb0067c6ed0572322080ae367ee38f9e7c9"
 dependencies = [
- "chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git)",
+ "chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
 ]
 
 [[package]]
 name = "chalk-solve"
 version = "0.1.0"
-source = "git+https://github.com/rust-lang/chalk.git#13303bb0067c6ed0572322080ae367ee38f9e7c9"
+source = "git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9#13303bb0067c6ed0572322080ae367ee38f9e7c9"
 dependencies = [
- "chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)",
+ "chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
  "ena 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "petgraph 0.4.13 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -979,9 +979,9 @@ name = "ra_hir"
 version = "0.1.0"
 dependencies = [
  "arrayvec 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)",
- "chalk-solve 0.1.0 (git+https://github.com/rust-lang/chalk.git)",
+ "chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
+ "chalk-solve 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)",
  "ena 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "insta 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lalrpop-intern 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1794,11 +1794,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum cargo_metadata 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8d2d1617e838936c0d2323a65cc151e03ae19a7678dd24f72bccf27119b90a5d"
 "checksum cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)" = "0213d356d3c4ea2c18c40b037c3be23cd639825c18f25ee670ac7813beeef99c"
 "checksum cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
-"checksum chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git)" = "<none>"
-"checksum chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)" = "<none>"
-"checksum chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git)" = "<none>"
-"checksum chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git)" = "<none>"
-"checksum chalk-solve 0.1.0 (git+https://github.com/rust-lang/chalk.git)" = "<none>"
+"checksum chalk-engine 0.9.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)" = "<none>"
+"checksum chalk-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)" = "<none>"
+"checksum chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)" = "<none>"
+"checksum chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)" = "<none>"
+"checksum chalk-solve 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=13303bb0067c6ed0572322080ae367ee38f9e7c9)" = "<none>"
 "checksum chrono 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)" = "e8493056968583b0193c1bb04d6f7684586f3726992d6c573261941a895dbd68"
 "checksum clicolors-control 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "90082ee5dcdd64dc4e9e0d37fbf3ee325419e39c0092191e0393df65518f741e"
 "checksum cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "ddfc5b9aa5d4507acaf872de71051dfd0e309860e88966e1051e462a077aac4f"
diff --git a/crates/ra_hir/Cargo.toml b/crates/ra_hir/Cargo.toml
index 54c09788a..dce897d30 100644
--- a/crates/ra_hir/Cargo.toml
+++ b/crates/ra_hir/Cargo.toml
@@ -22,9 +22,9 @@ tt = { path = "../ra_tt", package = "ra_tt" }
 test_utils = { path = "../test_utils" }
 ra_prof = { path = "../ra_prof" }
 
-chalk-solve = { git = "https://github.com/rust-lang/chalk.git" }
-chalk-rust-ir = { git = "https://github.com/rust-lang/chalk.git" }
-chalk-ir = { git = "https://github.com/rust-lang/chalk.git" }
+chalk-solve = { git = "https://github.com/rust-lang/chalk.git", rev = "13303bb0067c6ed0572322080ae367ee38f9e7c9" }
+chalk-rust-ir = { git = "https://github.com/rust-lang/chalk.git", rev = "13303bb0067c6ed0572322080ae367ee38f9e7c9" }
+chalk-ir = { git = "https://github.com/rust-lang/chalk.git", rev = "13303bb0067c6ed0572322080ae367ee38f9e7c9" }
 lalrpop-intern = "0.15.1"
 
 [dev-dependencies]
diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
index 0832229fd..d0188da44 100644
--- a/crates/ra_ide_api/src/lib.rs
+++ b/crates/ra_ide_api/src/lib.rs
@@ -14,6 +14,7 @@ mod db;
 pub mod mock_analysis;
 mod symbol_index;
 mod change;
+mod source_change;
 mod feature_flags;
 
 mod status;
@@ -54,8 +55,6 @@ use ra_db::{
     CheckCanceled, FileLoader, SourceDatabase,
 };
 use ra_syntax::{SourceFile, TextRange, TextUnit};
-use ra_text_edit::TextEdit;
-use relative_path::RelativePathBuf;
 
 use crate::{db::LineIndexDatabase, symbol_index::FileSymbol};
 
@@ -73,6 +72,7 @@ pub use crate::{
     line_index_utils::translate_offset_with_edit,
     references::{ReferenceSearchResult, SearchScope},
     runnables::{Runnable, RunnableKind},
+    source_change::{FileSystemEdit, SourceChange, SourceFileEdit},
     syntax_highlighting::HighlightedRange,
 };
 
@@ -84,99 +84,6 @@ pub use ra_db::{
 pub type Cancelable<T> = Result<T, Canceled>;
 
 #[derive(Debug)]
-pub struct SourceChange {
-    pub label: String,
-    pub source_file_edits: Vec<SourceFileEdit>,
-    pub file_system_edits: Vec<FileSystemEdit>,
-    pub cursor_position: Option<FilePosition>,
-}
-
-impl SourceChange {
-    /// Creates a new SourceChange with the given label
-    /// from the edits.
-    pub(crate) fn from_edits<L: Into<String>>(
-        label: L,
-        source_file_edits: Vec<SourceFileEdit>,
-        file_system_edits: Vec<FileSystemEdit>,
-    ) -> Self {
-        SourceChange {
-            label: label.into(),
-            source_file_edits,
-            file_system_edits,
-            cursor_position: None,
-        }
-    }
-
-    /// Creates a new SourceChange with the given label,
-    /// containing only the given `SourceFileEdits`.
-    pub(crate) fn source_file_edits<L: Into<String>>(label: L, edits: Vec<SourceFileEdit>) -> Self {
-        SourceChange {
-            label: label.into(),
-            source_file_edits: edits,
-            file_system_edits: vec![],
-            cursor_position: None,
-        }
-    }
-
-    /// Creates a new SourceChange with the given label,
-    /// containing only the given `FileSystemEdits`.
-    pub(crate) fn file_system_edits<L: Into<String>>(label: L, edits: Vec<FileSystemEdit>) -> Self {
-        SourceChange {
-            label: label.into(),
-            source_file_edits: vec![],
-            file_system_edits: edits,
-            cursor_position: None,
-        }
-    }
-
-    /// Creates a new SourceChange with the given label,
-    /// containing only a single `SourceFileEdit`.
-    pub(crate) fn source_file_edit<L: Into<String>>(label: L, edit: SourceFileEdit) -> Self {
-        SourceChange::source_file_edits(label, vec![edit])
-    }
-
-    /// Creates a new SourceChange with the given label
-    /// from the given `FileId` and `TextEdit`
-    pub(crate) fn source_file_edit_from<L: Into<String>>(
-        label: L,
-        file_id: FileId,
-        edit: TextEdit,
-    ) -> Self {
-        SourceChange::source_file_edit(label, SourceFileEdit { file_id, edit })
-    }
-
-    /// Creates a new SourceChange with the given label
-    /// from the given `FileId` and `TextEdit`
-    pub(crate) fn file_system_edit<L: Into<String>>(label: L, edit: FileSystemEdit) -> Self {
-        SourceChange::file_system_edits(label, vec![edit])
-    }
-
-    /// Sets the cursor position to the given `FilePosition`
-    pub(crate) fn with_cursor(mut self, cursor_position: FilePosition) -> Self {
-        self.cursor_position = Some(cursor_position);
-        self
-    }
-
-    /// Sets the cursor position to the given `FilePosition`
-    pub(crate) fn with_cursor_opt(mut self, cursor_position: Option<FilePosition>) -> Self {
-        self.cursor_position = cursor_position;
-        self
-    }
-}
-
-#[derive(Debug)]
-pub struct SourceFileEdit {
-    pub file_id: FileId,
-    pub edit: TextEdit,
-}
-
-#[derive(Debug)]
-pub enum FileSystemEdit {
-    CreateFile { source_root: SourceRootId, path: RelativePathBuf },
-    MoveFile { src: FileId, dst_source_root: SourceRootId, dst_path: RelativePathBuf },
-}
-
-#[derive(Debug)]
 pub struct Diagnostic {
     pub message: String,
     pub range: TextRange,
@@ -407,24 +314,20 @@ impl Analysis {
         self.with_db(|db| typing::on_enter(&db, position))
     }
 
-    /// Returns an edit which should be applied after `=` was typed. Primarily,
-    /// this works when adding `let =`.
-    // FIXME: use a snippet completion instead of this hack here.
-    pub fn on_eq_typed(&self, position: FilePosition) -> Cancelable<Option<SourceChange>> {
-        self.with_db(|db| {
-            let parse = db.parse(position.file_id);
-            let file = parse.tree();
-            let edit = typing::on_eq_typed(&file, position.offset)?;
-            Some(SourceChange::source_file_edit(
-                "add semicolon",
-                SourceFileEdit { edit, file_id: position.file_id },
-            ))
-        })
-    }
-
-    /// Returns an edit which should be applied when a dot ('.') is typed on a blank line, indenting the line appropriately.
-    pub fn on_dot_typed(&self, position: FilePosition) -> Cancelable<Option<SourceChange>> {
-        self.with_db(|db| typing::on_dot_typed(&db, position))
+    /// Returns an edit which should be applied after a character was typed.
+    ///
+    /// This is useful for some on-the-fly fixups, like adding `;` to `let =`
+    /// automatically.
+    pub fn on_char_typed(
+        &self,
+        position: FilePosition,
+        char_typed: char,
+    ) -> Cancelable<Option<SourceChange>> {
+        // Fast path to not even parse the file.
+        if !typing::TRIGGER_CHARS.contains(char_typed) {
+            return Ok(None);
+        }
+        self.with_db(|db| typing::on_char_typed(&db, position, char_typed))
     }
 
     /// Returns a tree representation of symbols in the file. Useful to draw a
diff --git a/crates/ra_ide_api/src/source_change.rs b/crates/ra_ide_api/src/source_change.rs
new file mode 100644
index 000000000..4e63bbf6f
--- /dev/null
+++ b/crates/ra_ide_api/src/source_change.rs
@@ -0,0 +1,119 @@
+//! This modules defines type to represent changes to the source code, that flow
+//! from the server to the client.
+//!
+//! It can be viewed as a dual for `AnalysisChange`.
+
+use ra_text_edit::TextEdit;
+use relative_path::RelativePathBuf;
+
+use crate::{FileId, FilePosition, SourceRootId, TextUnit};
+
+#[derive(Debug)]
+pub struct SourceChange {
+    pub label: String,
+    pub source_file_edits: Vec<SourceFileEdit>,
+    pub file_system_edits: Vec<FileSystemEdit>,
+    pub cursor_position: Option<FilePosition>,
+}
+
+impl SourceChange {
+    /// Creates a new SourceChange with the given label
+    /// from the edits.
+    pub(crate) fn from_edits<L: Into<String>>(
+        label: L,
+        source_file_edits: Vec<SourceFileEdit>,
+        file_system_edits: Vec<FileSystemEdit>,
+    ) -> Self {
+        SourceChange {
+            label: label.into(),
+            source_file_edits,
+            file_system_edits,
+            cursor_position: None,
+        }
+    }
+
+    /// Creates a new SourceChange with the given label,
+    /// containing only the given `SourceFileEdits`.
+    pub(crate) fn source_file_edits<L: Into<String>>(label: L, edits: Vec<SourceFileEdit>) -> Self {
+        SourceChange {
+            label: label.into(),
+            source_file_edits: edits,
+            file_system_edits: vec![],
+            cursor_position: None,
+        }
+    }
+
+    /// Creates a new SourceChange with the given label,
+    /// containing only the given `FileSystemEdits`.
+    pub(crate) fn file_system_edits<L: Into<String>>(label: L, edits: Vec<FileSystemEdit>) -> Self {
+        SourceChange {
+            label: label.into(),
+            source_file_edits: vec![],
+            file_system_edits: edits,
+            cursor_position: None,
+        }
+    }
+
+    /// Creates a new SourceChange with the given label,
+    /// containing only a single `SourceFileEdit`.
+    pub(crate) fn source_file_edit<L: Into<String>>(label: L, edit: SourceFileEdit) -> Self {
+        SourceChange::source_file_edits(label, vec![edit])
+    }
+
+    /// Creates a new SourceChange with the given label
+    /// from the given `FileId` and `TextEdit`
+    pub(crate) fn source_file_edit_from<L: Into<String>>(
+        label: L,
+        file_id: FileId,
+        edit: TextEdit,
+    ) -> Self {
+        SourceChange::source_file_edit(label, SourceFileEdit { file_id, edit })
+    }
+
+    /// Creates a new SourceChange with the given label
+    /// from the given `FileId` and `TextEdit`
+    pub(crate) fn file_system_edit<L: Into<String>>(label: L, edit: FileSystemEdit) -> Self {
+        SourceChange::file_system_edits(label, vec![edit])
+    }
+
+    /// Sets the cursor position to the given `FilePosition`
+    pub(crate) fn with_cursor(mut self, cursor_position: FilePosition) -> Self {
+        self.cursor_position = Some(cursor_position);
+        self
+    }
+
+    /// Sets the cursor position to the given `FilePosition`
+    pub(crate) fn with_cursor_opt(mut self, cursor_position: Option<FilePosition>) -> Self {
+        self.cursor_position = cursor_position;
+        self
+    }
+}
+
+#[derive(Debug)]
+pub struct SourceFileEdit {
+    pub file_id: FileId,
+    pub edit: TextEdit,
+}
+
+#[derive(Debug)]
+pub enum FileSystemEdit {
+    CreateFile { source_root: SourceRootId, path: RelativePathBuf },
+    MoveFile { src: FileId, dst_source_root: SourceRootId, dst_path: RelativePathBuf },
+}
+
+pub(crate) struct SingleFileChange {
+    pub label: String,
+    pub edit: TextEdit,
+    pub cursor_position: Option<TextUnit>,
+}
+
+impl SingleFileChange {
+    pub(crate) fn into_source_change(self, file_id: FileId) -> SourceChange {
+        SourceChange {
+            label: self.label,
+            source_file_edits: vec![SourceFileEdit { file_id, edit: self.edit }],
+            file_system_edits: Vec::new(),
+            cursor_position: self.cursor_position.map(|offset| FilePosition { file_id, offset }),
+        }
+    }
+}
diff --git a/crates/ra_ide_api/src/typing.rs b/crates/ra_ide_api/src/typing.rs
index 2f5782012..26a3111fd 100644
--- a/crates/ra_ide_api/src/typing.rs
+++ b/crates/ra_ide_api/src/typing.rs
@@ -1,4 +1,17 @@
-//! FIXME: write short doc here
+//! This module handles auto-magic editing actions applied together with users
+//! edits. For example, if the user typed
+//!
+//! ```text
+//!     foo
+//!         .bar()
+//!         .baz()
+//!     |   // <- cursor is here
+//! ```
+//!
+//! and types `.` next, we want to indent the dot.
+//!
+//! Language server executes such typing assists synchronously. That is, they
+//! block user's typing and should be pretty fast for this reason!
 
 use ra_db::{FilePosition, SourceDatabase};
 use ra_fmt::leading_indent;
@@ -11,7 +24,7 @@ use ra_syntax::{
 };
 use ra_text_edit::{TextEdit, TextEditBuilder};
 
-use crate::{db::RootDatabase, SourceChange, SourceFileEdit};
+use crate::{db::RootDatabase, source_change::SingleFileChange, SourceChange, SourceFileEdit};
 
 pub(crate) fn on_enter(db: &RootDatabase, position: FilePosition) -> Option<SourceChange> {
     let parse = db.parse(position.file_id);
@@ -68,39 +81,67 @@ fn node_indent(file: &SourceFile, token: &SyntaxToken) -> Option<SmolStr> {
     Some(text[pos..].into())
 }
 
-pub fn on_eq_typed(file: &SourceFile, eq_offset: TextUnit) -> Option<TextEdit> {
-    assert_eq!(file.syntax().text().char_at(eq_offset), Some('='));
-    let let_stmt: ast::LetStmt = find_node_at_offset(file.syntax(), eq_offset)?;
+pub(crate) const TRIGGER_CHARS: &str = ".=>";
+
+pub(crate) fn on_char_typed(
+    db: &RootDatabase,
+    position: FilePosition,
+    char_typed: char,
+) -> Option<SourceChange> {
+    assert!(TRIGGER_CHARS.contains(char_typed));
+    let file = &db.parse(position.file_id).tree();
+    assert_eq!(file.syntax().text().char_at(position.offset), Some(char_typed));
+    let single_file_change = on_char_typed_inner(file, position.offset, char_typed)?;
+    Some(single_file_change.into_source_change(position.file_id))
+}
+
+fn on_char_typed_inner(
+    file: &SourceFile,
+    offset: TextUnit,
+    char_typed: char,
+) -> Option<SingleFileChange> {
+    assert!(TRIGGER_CHARS.contains(char_typed));
+    match char_typed {
+        '.' => on_dot_typed(file, offset),
+        '=' => on_eq_typed(file, offset),
+        '>' => on_arrow_typed(file, offset),
+        _ => unreachable!(),
+    }
+}
+
+/// Returns an edit which should be applied after `=` was typed. Primarily,
+/// this works when adding `let =`.
+// FIXME: use a snippet completion instead of this hack here.
+fn on_eq_typed(file: &SourceFile, offset: TextUnit) -> Option<SingleFileChange> {
+    assert_eq!(file.syntax().text().char_at(offset), Some('='));
+    let let_stmt: ast::LetStmt = find_node_at_offset(file.syntax(), offset)?;
     if let_stmt.has_semi() {
         return None;
     }
     if let Some(expr) = let_stmt.initializer() {
         let expr_range = expr.syntax().text_range();
-        if expr_range.contains(eq_offset) && eq_offset != expr_range.start() {
+        if expr_range.contains(offset) && offset != expr_range.start() {
             return None;
         }
-        if file.syntax().text().slice(eq_offset..expr_range.start()).contains_char('\n') {
+        if file.syntax().text().slice(offset..expr_range.start()).contains_char('\n') {
             return None;
         }
     } else {
         return None;
     }
     let offset = let_stmt.syntax().text_range().end();
-    let mut edit = TextEditBuilder::default();
-    edit.insert(offset, ";".to_string());
-    Some(edit.finish())
+    Some(SingleFileChange {
+        label: "add semicolon".to_string(),
+        edit: TextEdit::insert(offset, ";".to_string()),
+        cursor_position: None,
+    })
 }
 
-pub(crate) fn on_dot_typed(db: &RootDatabase, position: FilePosition) -> Option<SourceChange> {
-    let parse = db.parse(position.file_id);
-    assert_eq!(parse.tree().syntax().text().char_at(position.offset), Some('.'));
-
-    let whitespace = parse
-        .tree()
-        .syntax()
-        .token_at_offset(position.offset)
-        .left_biased()
-        .and_then(ast::Whitespace::cast)?;
+/// Returns an edit which should be applied when a dot ('.') is typed on a blank line, indenting the line appropriately.
+fn on_dot_typed(file: &SourceFile, offset: TextUnit) -> Option<SingleFileChange> {
+    assert_eq!(file.syntax().text().char_at(offset), Some('.'));
+    let whitespace =
+        file.syntax().token_at_offset(offset).left_biased().and_then(ast::Whitespace::cast)?;
 
     let current_indent = {
         let text = whitespace.text();
@@ -117,20 +158,36 @@ pub(crate) fn on_dot_typed(db: &RootDatabase, position: FilePosition) -> Option<
     if current_indent_len == target_indent_len {
         return None;
     }
-    let mut edit = TextEditBuilder::default();
-    edit.replace(
-        TextRange::from_to(position.offset - current_indent_len, position.offset),
-        target_indent,
-    );
-
-    let res = SourceChange::source_file_edit_from("reindent dot", position.file_id, edit.finish())
-        .with_cursor(FilePosition {
-            offset: position.offset + target_indent_len - current_indent_len
-                + TextUnit::of_char('.'),
-            file_id: position.file_id,
-        });
-
-    Some(res)
+
+    Some(SingleFileChange {
+        label: "reindent dot".to_string(),
+        edit: TextEdit::replace(
+            TextRange::from_to(offset - current_indent_len, offset),
+            target_indent,
+        ),
+        cursor_position: Some(
+            offset + target_indent_len - current_indent_len + TextUnit::of_char('.'),
+        ),
+    })
+}
+
+/// Adds a space after an arrow when `fn foo() { ... }` is turned into `fn foo() -> { ... }`
+fn on_arrow_typed(file: &SourceFile, offset: TextUnit) -> Option<SingleFileChange> {
+    let file_text = file.syntax().text();
+    assert_eq!(file_text.char_at(offset), Some('>'));
+    let after_arrow = offset + TextUnit::of_char('>');
+    if file_text.char_at(after_arrow) != Some('{') {
+        return None;
+    }
+    if find_node_at_offset::<ast::RetType>(file.syntax(), offset).is_none() {
+        return None;
+    }
+
+    Some(SingleFileChange {
+        label: "add space after return type".to_string(),
+        edit: TextEdit::insert(after_arrow, " ".to_string()),
+        cursor_position: Some(after_arrow),
+    })
 }
 
 #[cfg(test)]
@@ -142,21 +199,87 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_on_eq_typed() {
-        fn type_eq(before: &str, after: &str) {
+    fn test_on_enter() {
+        fn apply_on_enter(before: &str) -> Option<String> {
             let (offset, before) = extract_offset(before);
-            let mut edit = TextEditBuilder::default();
-            edit.insert(offset, "=".to_string());
-            let before = edit.finish().apply(&before);
-            let parse = SourceFile::parse(&before);
-            if let Some(result) = on_eq_typed(&parse.tree(), offset) {
-                let actual = result.apply(&before);
-                assert_eq_text!(after, &actual);
-            } else {
-                assert_eq_text!(&before, after)
-            };
+            let (analysis, file_id) = single_file(&before);
+            let result = analysis.on_enter(FilePosition { offset, file_id }).unwrap()?;
+
+            assert_eq!(result.source_file_edits.len(), 1);
+            let actual = result.source_file_edits[0].edit.apply(&before);
+            let actual = add_cursor(&actual, result.cursor_position.unwrap().offset);
+            Some(actual)
+        }
+
+        fn do_check(before: &str, after: &str) {
+            let actual = apply_on_enter(before).unwrap();
+            assert_eq_text!(after, &actual);
+        }
+
+        fn do_check_noop(text: &str) {
+            assert!(apply_on_enter(text).is_none())
+        }
+
+        do_check(
+            r"
+/// Some docs<|>
+fn foo() {
+}
+",
+            r"
+/// Some docs
+/// <|>
+fn foo() {
+}
+",
+        );
+        do_check(
+            r"
+impl S {
+    /// Some<|> docs.
+    fn foo() {}
+}
+",
+            r"
+impl S {
+    /// Some
+    /// <|> docs.
+    fn foo() {}
+}
+",
+        );
+        do_check_noop(r"<|>//! docz");
+    }
+
+    fn do_type_char(char_typed: char, before: &str) -> Option<(String, SingleFileChange)> {
+        let (offset, before) = extract_offset(before);
+        let edit = TextEdit::insert(offset, char_typed.to_string());
+        let before = edit.apply(&before);
+        let parse = SourceFile::parse(&before);
+        on_char_typed_inner(&parse.tree(), offset, char_typed)
+            .map(|it| (it.edit.apply(&before), it))
+    }
+
+    fn type_char(char_typed: char, before: &str, after: &str) {
+        let (actual, file_change) = do_type_char(char_typed, before)
+            .expect(&format!("typing `{}` did nothing", char_typed));
+
+        if after.contains("<|>") {
+            let (offset, after) = extract_offset(after);
+            assert_eq_text!(&after, &actual);
+            assert_eq!(file_change.cursor_position, Some(offset))
+        } else {
+            assert_eq_text!(after, &actual);
         }
+    }
 
+    fn type_char_noop(char_typed: char, before: &str) {
+        let file_change = do_type_char(char_typed, before);
+        assert!(file_change.is_none())
+    }
+
+    #[test]
+    fn test_on_eq_typed() {
         //     do_check(r"
         // fn foo() {
         //     let foo =<|>
@@ -166,7 +289,8 @@ mod tests {
         //     let foo =;
         // }
         // ");
-        type_eq(
+        type_char(
+            '=',
             r"
 fn foo() {
     let foo <|> 1 + 1
@@ -191,24 +315,10 @@ fn foo() {
         // ");
     }
 
-    fn type_dot(before: &str, after: &str) {
-        let (offset, before) = extract_offset(before);
-        let mut edit = TextEditBuilder::default();
-        edit.insert(offset, ".".to_string());
-        let before = edit.finish().apply(&before);
-        let (analysis, file_id) = single_file(&before);
-        if let Some(result) = analysis.on_dot_typed(FilePosition { offset, file_id }).unwrap() {
-            assert_eq!(result.source_file_edits.len(), 1);
-            let actual = result.source_file_edits[0].edit.apply(&before);
-            assert_eq_text!(after, &actual);
-        } else {
-            assert_eq_text!(&before, after)
-        };
-    }
-
     #[test]
     fn indents_new_chain_call() {
-        type_dot(
+        type_char(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 self.child_impl(db, name)
@@ -222,25 +332,21 @@ fn foo() {
             }
             ",
         );
-        type_dot(
+        type_char_noop(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 self.child_impl(db, name)
                     <|>
             }
             ",
-            r"
-            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
-                self.child_impl(db, name)
-                    .
-            }
-            ",
         )
     }
 
     #[test]
     fn indents_new_chain_call_with_semi() {
-        type_dot(
+        type_char(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 self.child_impl(db, name)
@@ -254,25 +360,21 @@ fn foo() {
             }
             ",
         );
-        type_dot(
+        type_char_noop(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 self.child_impl(db, name)
                     <|>;
             }
             ",
-            r"
-            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
-                self.child_impl(db, name)
-                    .;
-            }
-            ",
         )
     }
 
     #[test]
     fn indents_continued_chain_call() {
-        type_dot(
+        type_char(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 self.child_impl(db, name)
@@ -288,7 +390,8 @@ fn foo() {
             }
             ",
         );
-        type_dot(
+        type_char_noop(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 self.child_impl(db, name)
@@ -296,19 +399,13 @@ fn foo() {
                     <|>
             }
             ",
-            r"
-            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
-                self.child_impl(db, name)
-                    .first()
-                    .
-            }
-            ",
         );
     }
 
     #[test]
     fn indents_middle_of_chain_call() {
-        type_dot(
+        type_char(
+            '.',
             r"
             fn source_impl() {
                 let var = enum_defvariant_list().unwrap()
@@ -326,7 +423,8 @@ fn foo() {
             }
             ",
         );
-        type_dot(
+        type_char_noop(
+            '.',
             r"
             fn source_impl() {
                 let var = enum_defvariant_list().unwrap()
@@ -335,95 +433,31 @@ fn foo() {
                     .unwrap();
             }
             ",
-            r"
-            fn source_impl() {
-                let var = enum_defvariant_list().unwrap()
-                    .
-                    .nth(92)
-                    .unwrap();
-            }
-            ",
         );
     }
 
     #[test]
     fn dont_indent_freestanding_dot() {
-        type_dot(
+        type_char_noop(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
                 <|>
             }
             ",
-            r"
-            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
-                .
-            }
-            ",
         );
-        type_dot(
+        type_char_noop(
+            '.',
             r"
             pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
             <|>
             }
             ",
-            r"
-            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
-            .
-            }
-            ",
         );
     }
 
     #[test]
-    fn test_on_enter() {
-        fn apply_on_enter(before: &str) -> Option<String> {
-            let (offset, before) = extract_offset(before);
-            let (analysis, file_id) = single_file(&before);
-            let result = analysis.on_enter(FilePosition { offset, file_id }).unwrap()?;
-
-            assert_eq!(result.source_file_edits.len(), 1);
-            let actual = result.source_file_edits[0].edit.apply(&before);
-            let actual = add_cursor(&actual, result.cursor_position.unwrap().offset);
-            Some(actual)
-        }
-
-        fn do_check(before: &str, after: &str) {
-            let actual = apply_on_enter(before).unwrap();
-            assert_eq_text!(after, &actual);
-        }
-
-        fn do_check_noop(text: &str) {
-            assert!(apply_on_enter(text).is_none())
-        }
-
-        do_check(
-            r"
-/// Some docs<|>
-fn foo() {
-}
-",
-            r"
-/// Some docs
-/// <|>
-fn foo() {
-}
-",
-        );
-        do_check(
-            r"
-impl S {
-    /// Some<|> docs.
-    fn foo() {}
-}
-",
-            r"
-impl S {
-    /// Some
-    /// <|> docs.
-    fn foo() {}
-}
-",
-        );
-        do_check_noop(r"<|>//! docz");
+    fn adds_space_after_return_type() {
+        type_char('>', "fn foo() -<|>{ 92 }", "fn foo() -><|> { 92 }")
     }
 }
diff --git a/crates/ra_lsp_server/src/caps.rs b/crates/ra_lsp_server/src/caps.rs
index 30bcbd7a8..eea0965ed 100644
--- a/crates/ra_lsp_server/src/caps.rs
+++ b/crates/ra_lsp_server/src/caps.rs
@@ -38,7 +38,7 @@ pub fn server_capabilities() -> ServerCapabilities {
         document_range_formatting_provider: None,
         document_on_type_formatting_provider: Some(DocumentOnTypeFormattingOptions {
             first_trigger_character: "=".to_string(),
-            more_trigger_character: Some(vec![".".to_string()]),
+            more_trigger_character: Some(vec![".".to_string(), ">".to_string()]),
         }),
         selection_range_provider: Some(GenericCapability::default()),
         folding_range_provider: Some(FoldingRangeProviderCapability::Simple(true)),
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index a29971d10..16fb07266 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -132,6 +132,7 @@ pub fn handle_on_enter(
     }
 }
 
+// Don't forget to add new trigger characters to `ServerCapabilities` in `caps.rs`.
 pub fn handle_on_type_formatting(
     world: WorldSnapshot,
     params: req::DocumentOnTypeFormattingParams,
@@ -144,12 +145,17 @@ pub fn handle_on_type_formatting(
     // in `ra_ide_api`, the `on_type` invariant is that
     // `text.char_at(position) == typed_char`.
     position.offset = position.offset - TextUnit::of_char('.');
+    let char_typed = params.ch.chars().next().unwrap_or('\0');
 
-    let edit = match params.ch.as_str() {
-        "=" => world.analysis().on_eq_typed(position),
-        "." => world.analysis().on_dot_typed(position),
-        _ => return Ok(None),
-    }?;
+    // We have an assist that inserts ` ` after typing `->` in `fn foo() ->{`,
+    // but it requires precise cursor positioning to work, and one can't
+    // position the cursor with on_type formatting. So, let's just toggle this
+    // feature off here, hoping that we'll enable it one day, 😿.
+    if char_typed == '>' {
+        return Ok(None);
+    }
+
+    let edit = world.analysis().on_char_typed(position, char_typed)?;
     let mut edit = match edit {
         Some(it) => it,
         None => return Ok(None),
diff --git a/crates/ra_text_edit/src/text_edit.rs b/crates/ra_text_edit/src/text_edit.rs
index 0381ea000..413c7d782 100644
--- a/crates/ra_text_edit/src/text_edit.rs
+++ b/crates/ra_text_edit/src/text_edit.rs
@@ -32,6 +32,24 @@ impl TextEditBuilder {
 }
 
 impl TextEdit {
+    pub fn insert(offset: TextUnit, text: String) -> TextEdit {
+        let mut builder = TextEditBuilder::default();
+        builder.insert(offset, text);
+        builder.finish()
+    }
+
+    pub fn delete(range: TextRange) -> TextEdit {
+        let mut builder = TextEditBuilder::default();
+        builder.delete(range);
+        builder.finish()
+    }
+
+    pub fn replace(range: TextRange, replace_with: String) -> TextEdit {
+        let mut builder = TextEditBuilder::default();
+        builder.replace(range, replace_with);
+        builder.finish()
+    }
+
     pub(crate) fn from_atoms(mut atoms: Vec<AtomTextEdit>) -> TextEdit {
         atoms.sort_by_key(|a| (a.delete.start(), a.delete.end()));
         for (a1, a2) in atoms.iter().zip(atoms.iter().skip(1)) {