13 files changed, 114 insertions, 87 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 275b27775..69b78e7de 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -761,7 +761,7 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.0.2"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -897,7 +897,7 @@ dependencies = [
  "format-buf 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "join_to_string 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "once_cell 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_db 0.1.0",
  "ra_fmt 0.1.0",
  "ra_hir 0.1.0",
@@ -968,7 +968,7 @@ dependencies = [
  "insta 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lalrpop-intern 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "once_cell 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_arena 0.1.0",
  "ra_db 0.1.0",
@@ -1065,7 +1065,7 @@ dependencies = [
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "jemalloc-ctl 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "jemallocator 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "once_cell 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1085,7 +1085,9 @@ dependencies = [
 name = "ra_syntax"
 version = "0.1.0"
 dependencies = [
+ "arrayvec 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_parser 0.1.0",
  "ra_text_edit 0.1.0",
  "rowan 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1854,7 +1856,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "6ba9a427cfca2be13aa6f6403b0b7e7368fe982bfa16fccc450ce74c46cd9b32"
 "checksum num_cpus 1.10.1 (registry+https://github.com/rust-lang/crates.io-index)" = "bcef43580c035376c0705c42792c294b66974abbfd2789b511784023f71f3273"
 "checksum number_prefix 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "dbf9993e59c894e3c08aa1c2712914e9e6bf1fcbfc6bef283e2183df345a4fee"
-"checksum once_cell 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "bd38c1bb51148ca239ec38ef1bb4f7570d432861f03e91774d53b01c2ba2132f"
+"checksum once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "891f486f630e5c5a4916c7e16c4b24a53e78c860b646e9f8e005e4f16847bfed"
 "checksum ordermap 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "a86ed3f5f244b372d6b1a00b72ef7f8876d0bc6a78a4c9985c53614041512063"
 "checksum parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f842b1982eb6c2fe34036a4fbfb06dd185a3f5c8edfaacdf7d1ea10b07de6252"
 "checksum parking_lot_core 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "b876b1b9e7ac6e1a74a6da34d25c42e17e8862aa409cbbbdcfc8d86c6f3bc62b"
diff --git a/crates/ra_assists/src/assists/add_missing_impl_members.rs b/crates/ra_assists/src/assists/add_missing_impl_members.rs
index 23da1e65f..682455bce 100644
--- a/crates/ra_assists/src/assists/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/assists/add_missing_impl_members.rs
@@ -100,12 +100,11 @@ fn strip_docstring(item: ast::ImplItem) -> ast::ImplItem {
 }
 
 fn add_body(fn_def: ast::FnDef) -> ast::FnDef {
-    let mut ast_editor = AstEditor::new(fn_def.clone());
     if fn_def.body().is_none() {
-        let body = make::block_from_expr(make::expr_unimplemented());
-        ast_editor.set_body(&body);
+        fn_def.with_body(make::block_from_expr(make::expr_unimplemented()))
+    } else {
+        fn_def
     }
-    ast_editor.ast().to_owned()
 }
 
 /// Given an `ast::ImplBlock`, resolves the target trait (the one being
@@ -332,5 +331,4 @@ impl Foo for S {
 }",
         )
     }
-
 }
diff --git a/crates/ra_assists/src/assists/auto_import.rs b/crates/ra_assists/src/assists/auto_import.rs
index 5aae98546..a91c170b9 100644
--- a/crates/ra_assists/src/assists/auto_import.rs
+++ b/crates/ra_assists/src/assists/auto_import.rs
@@ -448,7 +448,6 @@ fn make_assist_add_in_tree_list(
         fmt_segments_raw(target, &mut buf);
         edit.insert(offset, buf);
     } else {
-
     }
 }
 
diff --git a/crates/ra_assists/src/ast_editor.rs b/crates/ra_assists/src/ast_editor.rs
index 2a685f26e..72c8c478a 100644
--- a/crates/ra_assists/src/ast_editor.rs
+++ b/crates/ra_assists/src/ast_editor.rs
@@ -6,7 +6,7 @@ use rustc_hash::FxHashMap;
 use ra_fmt::leading_indent;
 use ra_syntax::{
     algo,
-    ast::{self, TypeBoundsOwner},
+    ast::{self, make::tokens, TypeBoundsOwner},
     AstNode, Direction, InsertPosition, SyntaxElement,
     SyntaxKind::*,
     T,
@@ -229,26 +229,6 @@ impl AstEditor<ast::ImplItem> {
     }
 }
 
-impl AstEditor<ast::FnDef> {
-    pub fn set_body(&mut self, body: &ast::Block) {
-        let mut to_insert: ArrayVec<[SyntaxElement; 2]> = ArrayVec::new();
-        let old_body_or_semi: SyntaxElement = if let Some(old_body) = self.ast().body() {
-            old_body.syntax().clone().into()
-        } else if let Some(semi) = self.ast().semicolon_token() {
-            to_insert.push(tokens::single_space().into());
-            semi.into()
-        } else {
-            to_insert.push(tokens::single_space().into());
-            to_insert.push(body.syntax().clone().into());
-            self.ast = self.insert_children(InsertPosition::Last, to_insert.into_iter());
-            return;
-        };
-        to_insert.push(body.syntax().clone().into());
-        let replace_range = RangeInclusive::new(old_body_or_semi.clone(), old_body_or_semi);
-        self.ast = self.replace_children(replace_range, to_insert.into_iter())
-    }
-}
-
 impl AstEditor<ast::TypeParam> {
     pub fn remove_bounds(&mut self) -> &mut Self {
         let colon = match self.ast.colon_token() {
@@ -263,53 +243,3 @@ impl AstEditor<ast::TypeParam> {
         self
     }
 }
-
-mod tokens {
-    use once_cell::sync::Lazy;
-    use ra_syntax::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
-
-    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
-
-    pub(crate) fn comma() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == T![,])
-            .unwrap()
-    }
-
-    pub(crate) fn single_space() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == " ")
-            .unwrap()
-    }
-
-    #[allow(unused)]
-    pub(crate) fn single_newline() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == "\n")
-            .unwrap()
-    }
-
-    pub(crate) struct WsBuilder(SourceFile);
-
-    impl WsBuilder {
-        pub(crate) fn new(text: &str) -> WsBuilder {
-            WsBuilder(SourceFile::parse(text).ok().unwrap())
-        }
-        pub(crate) fn ws(&self) -> SyntaxToken {
-            self.0.syntax().first_child_or_token().unwrap().into_token().unwrap()
-        }
-    }
-
-}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 897af2b02..3ca3320f7 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -340,5 +340,4 @@ mod tests {
         assert_eq!(assists.next().expect("expected assist").0.label, "introduce variable");
         assert_eq!(assists.next().expect("expected assist").0.label, "replace with match");
     }
-
 }
diff --git a/crates/ra_ide_api/src/line_index.rs b/crates/ra_ide_api/src/line_index.rs
index 71de8a928..5fedad696 100644
--- a/crates/ra_ide_api/src/line_index.rs
+++ b/crates/ra_ide_api/src/line_index.rs
@@ -278,5 +278,4 @@ const C: char = \"メ メ\";
 
         assert_eq!(col_index.utf16_to_utf8_col(2, 15), TextUnit::from_usize(15));
     }
-
 }
diff --git a/crates/ra_ide_api/src/runnables.rs b/crates/ra_ide_api/src/runnables.rs
index 095ca56c4..8cf58fe79 100644
--- a/crates/ra_ide_api/src/runnables.rs
+++ b/crates/ra_ide_api/src/runnables.rs
@@ -229,5 +229,4 @@ mod tests {
         let runnables = analysis.runnables(pos.file_id).unwrap();
         assert!(runnables.is_empty())
     }
-
 }
diff --git a/crates/ra_lsp_server/src/markdown.rs b/crates/ra_lsp_server/src/markdown.rs
index c1eb0236a..3659edf8e 100644
--- a/crates/ra_lsp_server/src/markdown.rs
+++ b/crates/ra_lsp_server/src/markdown.rs
@@ -70,5 +70,4 @@ let a = 1;
             "```rust\nfn main(){}\n```\nSome comment.\n```rust\nlet a = 1;\n```"
         );
     }
-
 }
diff --git a/crates/ra_parser/src/grammar.rs b/crates/ra_parser/src/grammar.rs
index e2355aff9..6e9e212b7 100644
--- a/crates/ra_parser/src/grammar.rs
+++ b/crates/ra_parser/src/grammar.rs
@@ -135,7 +135,6 @@ pub(crate) mod fragments {
 
         m.complete(p, MACRO_STMTS);
     }
-
 }
 
 pub(crate) fn reparser(
diff --git a/crates/ra_syntax/Cargo.toml b/crates/ra_syntax/Cargo.toml
index 724c38e17..9bc85404a 100644
--- a/crates/ra_syntax/Cargo.toml
+++ b/crates/ra_syntax/Cargo.toml
@@ -12,6 +12,8 @@ itertools = "0.8.0"
 rowan = "0.6.1"
 rustc_lexer = "0.1.0"
 rustc-hash = "1.0.1"
+arrayvec = "0.4.10"
+once_cell = "1.2.0"
 
 # ideally, `serde` should be enabled by `ra_lsp_server`, but we enable it here
 # to reduce number of compilations
diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index f464d6534..fdffd8cb1 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -5,6 +5,7 @@ mod traits;
 mod tokens;
 mod extensions;
 mod expr_extensions;
+mod edit;
 pub mod make;
 
 use std::marker::PhantomData;
diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
new file mode 100644
index 000000000..c65899812
--- /dev/null
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -0,0 +1,52 @@
+//! This module contains functions for editing syntax trees. As the trees are
+//! immutable, all function here return a fresh copy of the tree, instead of
+//! doing an in-place modification.
+
+use arrayvec::ArrayVec;
+use std::ops::RangeInclusive;
+
+use crate::{
+    algo,
+    ast::{self, make, AstNode},
+    InsertPosition, SyntaxElement,
+};
+
+impl ast::FnDef {
+    #[must_use]
+    pub fn with_body(&self, body: ast::Block) -> ast::FnDef {
+        let mut to_insert: ArrayVec<[SyntaxElement; 2]> = ArrayVec::new();
+        let old_body_or_semi: SyntaxElement = if let Some(old_body) = self.body() {
+            old_body.syntax().clone().into()
+        } else if let Some(semi) = self.semicolon_token() {
+            to_insert.push(make::tokens::single_space().into());
+            semi.into()
+        } else {
+            to_insert.push(make::tokens::single_space().into());
+            to_insert.push(body.syntax().clone().into());
+            return insert_children(self, InsertPosition::Last, to_insert.into_iter());
+        };
+        to_insert.push(body.syntax().clone().into());
+        let replace_range = RangeInclusive::new(old_body_or_semi.clone(), old_body_or_semi);
+        replace_children(self, replace_range, to_insert.into_iter())
+    }
+}
+
+#[must_use]
+fn insert_children<N: AstNode>(
+    parent: &N,
+    position: InsertPosition<SyntaxElement>,
+    mut to_insert: impl Iterator<Item = SyntaxElement>,
+) -> N {
+    let new_syntax = algo::insert_children(parent.syntax(), position, &mut to_insert);
+    N::cast(new_syntax).unwrap()
+}
+
+#[must_use]
+fn replace_children<N: AstNode>(
+    parent: &N,
+    to_replace: RangeInclusive<SyntaxElement>,
+    mut to_insert: impl Iterator<Item = SyntaxElement>,
+) -> N {
+    let new_syntax = algo::replace_children(parent.syntax(), to_replace, &mut to_insert);
+    N::cast(new_syntax).unwrap()
+}
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index c06c62b3b..287a40bee 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -133,3 +133,51 @@ fn ast_from_text<N: AstNode>(text: &str) -> N {
     let res = parse.tree().syntax().descendants().find_map(N::cast).unwrap();
     res
 }
+
+pub mod tokens {
+    use crate::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
+    use once_cell::sync::Lazy;
+
+    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
+
+    pub fn comma() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == T![,])
+            .unwrap()
+    }
+
+    pub fn single_space() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == " ")
+            .unwrap()
+    }
+
+    pub fn single_newline() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == "\n")
+            .unwrap()
+    }
+
+    pub struct WsBuilder(SourceFile);
+
+    impl WsBuilder {
+        pub fn new(text: &str) -> WsBuilder {
+            WsBuilder(SourceFile::parse(text).ok().unwrap())
+        }
+        pub fn ws(&self) -> SyntaxToken {
+            self.0.syntax().first_child_or_token().unwrap().into_token().unwrap()
+        }
+    }
+}