46 files changed, 1194 insertions, 394 deletions

diff --git a/crates/ra_assists/Cargo.toml b/crates/ra_assists/Cargo.toml
index d314dc8e6..a87f4052a 100644
--- a/crates/ra_assists/Cargo.toml
+++ b/crates/ra_assists/Cargo.toml
@@ -11,6 +11,8 @@ doctest = false
 format-buf = "1.0.0"
 join_to_string = "0.1.3"
 rustc-hash = "1.1.0"
+itertools = "0.9.0"
+either = "1.5.3"
 
 ra_syntax = { path = "../ra_syntax" }
 ra_text_edit = { path = "../ra_text_edit" }
diff --git a/crates/ra_assists/src/assist_ctx.rs b/crates/ra_assists/src/assist_ctx.rs
index 62182cf03..c3e653299 100644
--- a/crates/ra_assists/src/assist_ctx.rs
+++ b/crates/ra_assists/src/assist_ctx.rs
@@ -11,6 +11,7 @@ use ra_syntax::{
 use ra_text_edit::TextEditBuilder;
 
 use crate::{AssistAction, AssistId, AssistLabel, GroupLabel, ResolvedAssist};
+use algo::SyntaxRewriter;
 
 #[derive(Clone, Debug)]
 pub(crate) struct Assist(pub(crate) Vec<AssistInfo>);
@@ -234,6 +235,11 @@ impl ActionBuilder {
     pub(crate) fn replace_ast<N: AstNode>(&mut self, old: N, new: N) {
         algo::diff(old.syntax(), new.syntax()).into_text_edit(&mut self.edit)
     }
+    pub(crate) fn rewrite(&mut self, rewriter: SyntaxRewriter) {
+        let node = rewriter.rewrite_root().unwrap();
+        let new = rewriter.rewrite(&node);
+        algo::diff(&node, &new).into_text_edit(&mut self.edit)
+    }
 
     fn build(self) -> AssistAction {
         AssistAction {
diff --git a/crates/ra_assists/src/ast_transform.rs b/crates/ra_assists/src/ast_transform.rs
index 45558c448..52b4c82db 100644
--- a/crates/ra_assists/src/ast_transform.rs
+++ b/crates/ra_assists/src/ast_transform.rs
@@ -3,7 +3,10 @@ use rustc_hash::FxHashMap;
 
 use hir::{PathResolution, SemanticsScope};
 use ra_ide_db::RootDatabase;
-use ra_syntax::ast::{self, AstNode};
+use ra_syntax::{
+    algo::SyntaxRewriter,
+    ast::{self, AstNode},
+};
 
 pub trait AstTransform<'a> {
     fn get_substitution(&self, node: &ra_syntax::SyntaxNode) -> Option<ra_syntax::SyntaxNode>;
@@ -153,15 +156,14 @@ impl<'a> QualifyPaths<'a> {
 }
 
 pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
-    let syntax = node.syntax();
-    let result = ra_syntax::algo::replace_descendants(syntax, |element| match element {
+    SyntaxRewriter::from_fn(|element| match element {
         ra_syntax::SyntaxElement::Node(n) => {
             let replacement = transformer.get_substitution(&n)?;
             Some(replacement.into())
         }
         _ => None,
-    });
-    N::cast(result).unwrap()
+    })
+    .rewrite_ast(&node)
 }
 
 impl<'a> AstTransform<'a> for QualifyPaths<'a> {
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index aef6793e8..62dcb3808 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -275,8 +275,8 @@ enum Action { Move { distance: u32 }, Stop }
 
 fn handle(action: Action) {
     match action {
-        Action::Move { distance } => (),
-        Action::Stop => (),
+        Action::Move { distance } => {}
+        Action::Stop => {}
     }
 }
 "#####,
diff --git a/crates/ra_assists/src/handlers/add_missing_impl_members.rs b/crates/ra_assists/src/handlers/add_missing_impl_members.rs
index e5920b6f6..722f207e2 100644
--- a/crates/ra_assists/src/handlers/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/handlers/add_missing_impl_members.rs
@@ -151,7 +151,7 @@ fn add_missing_impl_members_inner(
                 ast::ImplItem::FnDef(def) => ast::ImplItem::FnDef(add_body(def)),
                 _ => it,
             })
-            .map(|it| edit::strip_attrs_and_docs(&it));
+            .map(|it| edit::remove_attrs_and_docs(&it));
         let new_impl_item_list = impl_item_list.append_items(items);
         let cursor_position = {
             let first_new_item = new_impl_item_list.impl_items().nth(n_existing_items).unwrap();
diff --git a/crates/ra_assists/src/handlers/auto_import.rs b/crates/ra_assists/src/handlers/auto_import.rs
index bb280f633..99682e023 100644
--- a/crates/ra_assists/src/handlers/auto_import.rs
+++ b/crates/ra_assists/src/handlers/auto_import.rs
@@ -17,6 +17,7 @@ use crate::{
     utils::insert_use_statement,
     AssistId,
 };
+use either::Either;
 
 // Assist: auto_import
 //
@@ -58,6 +59,7 @@ pub(crate) fn auto_import(ctx: AssistCtx) -> Option<Assist> {
     group.finish()
 }
 
+#[derive(Debug)]
 struct AutoImportAssets {
     import_candidate: ImportCandidate,
     module_with_name_to_import: Module,
@@ -127,14 +129,14 @@ impl AutoImportAssets {
         ImportsLocator::new(db)
             .find_imports(&self.get_search_query())
             .into_iter()
-            .filter_map(|module_def| match &self.import_candidate {
+            .filter_map(|candidate| match &self.import_candidate {
                 ImportCandidate::TraitAssocItem(assoc_item_type, _) => {
-                    let located_assoc_item = match module_def {
-                        ModuleDef::Function(located_function) => located_function
+                    let located_assoc_item = match candidate {
+                        Either::Left(ModuleDef::Function(located_function)) => located_function
                             .as_assoc_item(db)
                             .map(|assoc| assoc.container(db))
                             .and_then(Self::assoc_to_trait),
-                        ModuleDef::Const(located_const) => located_const
+                        Either::Left(ModuleDef::Const(located_const)) => located_const
                             .as_assoc_item(db)
                             .map(|assoc| assoc.container(db))
                             .and_then(Self::assoc_to_trait),
@@ -153,10 +155,11 @@ impl AutoImportAssets {
                             |_, assoc| Self::assoc_to_trait(assoc.container(db)),
                         )
                         .map(ModuleDef::from)
+                        .map(Either::Left)
                 }
                 ImportCandidate::TraitMethod(function_callee, _) => {
                     let located_assoc_item =
-                        if let ModuleDef::Function(located_function) = module_def {
+                        if let Either::Left(ModuleDef::Function(located_function)) = candidate {
                             located_function
                                 .as_assoc_item(db)
                                 .map(|assoc| assoc.container(db))
@@ -179,10 +182,18 @@ impl AutoImportAssets {
                             },
                         )
                         .map(ModuleDef::from)
+                        .map(Either::Left)
+                }
+                _ => Some(candidate),
+            })
+            .filter_map(|candidate| match candidate {
+                Either::Left(module_def) => {
+                    self.module_with_name_to_import.find_use_path(db, module_def)
+                }
+                Either::Right(macro_def) => {
+                    self.module_with_name_to_import.find_use_path(db, macro_def)
                 }
-                _ => Some(module_def),
             })
-            .filter_map(|module_def| self.module_with_name_to_import.find_use_path(db, module_def))
             .filter(|use_path| !use_path.segments.is_empty())
             .take(20)
             .collect::<BTreeSet<_>>()
@@ -440,6 +451,30 @@ mod tests {
     }
 
     #[test]
+    fn macro_import() {
+        check_assist(
+            auto_import,
+            r"
+                    //- /lib.rs crate:crate_with_macro
+                    #[macro_export]
+                    macro_rules! foo {
+                        () => ()
+                    }
+
+                    //- /main.rs crate:main deps:crate_with_macro
+                    fn main() {
+                        foo<|>
+                    }",
+            r"use crate_with_macro::foo;
+
+fn main() {
+    foo<|>
+}
+",
+        );
+    }
+
+    #[test]
     fn auto_import_target() {
         check_assist_target(
             auto_import,
diff --git a/crates/ra_assists/src/handlers/fill_match_arms.rs b/crates/ra_assists/src/handlers/fill_match_arms.rs
index fbd6a3ec3..add82e5b1 100644
--- a/crates/ra_assists/src/handlers/fill_match_arms.rs
+++ b/crates/ra_assists/src/handlers/fill_match_arms.rs
@@ -2,7 +2,8 @@
 
 use std::iter;
 
-use hir::{Adt, HasSource, Semantics};
+use hir::{Adt, HasSource, ModuleDef, Semantics};
+use itertools::Itertools;
 use ra_ide_db::RootDatabase;
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -29,8 +30,8 @@ use ast::{MatchArm, Pat};
 //
 // fn handle(action: Action) {
 //     match action {
-//         Action::Move { distance } => (),
-//         Action::Stop => (),
+//         Action::Move { distance } => {}
+//         Action::Stop => {}
 //     }
 // }
 // ```
@@ -39,13 +40,6 @@ pub(crate) fn fill_match_arms(ctx: AssistCtx) -> Option<Assist> {
     let match_arm_list = match_expr.match_arm_list()?;
 
     let expr = match_expr.expr()?;
-    let enum_def = resolve_enum_def(&ctx.sema, &expr)?;
-    let module = ctx.sema.scope(expr.syntax()).module()?;
-
-    let variants = enum_def.variants(ctx.db);
-    if variants.is_empty() {
-        return None;
-    }
 
     let mut arms: Vec<MatchArm> = match_arm_list.arms().collect();
     if arms.len() == 1 {
@@ -54,13 +48,49 @@ pub(crate) fn fill_match_arms(ctx: AssistCtx) -> Option<Assist> {
         }
     }
 
-    let db = ctx.db;
-    let missing_arms: Vec<MatchArm> = variants
-        .into_iter()
-        .filter_map(|variant| build_pat(db, module, variant))
-        .filter(|variant_pat| is_variant_missing(&mut arms, variant_pat))
-        .map(|pat| make::match_arm(iter::once(pat), make::expr_unit()))
-        .collect();
+    let module = ctx.sema.scope(expr.syntax()).module()?;
+
+    let missing_arms: Vec<MatchArm> = if let Some(enum_def) = resolve_enum_def(&ctx.sema, &expr) {
+        let variants = enum_def.variants(ctx.db);
+
+        variants
+            .into_iter()
+            .filter_map(|variant| build_pat(ctx.db, module, variant))
+            .filter(|variant_pat| is_variant_missing(&mut arms, variant_pat))
+            .map(|pat| make::match_arm(iter::once(pat), make::expr_empty_block()))
+            .collect()
+    } else if let Some(enum_defs) = resolve_tuple_of_enum_def(&ctx.sema, &expr) {
+        // Partial fill not currently supported for tuple of enums.
+        if !arms.is_empty() {
+            return None;
+        }
+
+        // We do not currently support filling match arms for a tuple
+        // containing a single enum.
+        if enum_defs.len() < 2 {
+            return None;
+        }
+
+        // When calculating the match arms for a tuple of enums, we want
+        // to create a match arm for each possible combination of enum
+        // values. The `multi_cartesian_product` method transforms
+        // Vec<Vec<EnumVariant>> into Vec<(EnumVariant, .., EnumVariant)>
+        // where each tuple represents a proposed match arm.
+        enum_defs
+            .into_iter()
+            .map(|enum_def| enum_def.variants(ctx.db))
+            .multi_cartesian_product()
+            .map(|variants| {
+                let patterns =
+                    variants.into_iter().filter_map(|variant| build_pat(ctx.db, module, variant));
+                ast::Pat::from(make::tuple_pat(patterns))
+            })
+            .filter(|variant_pat| is_variant_missing(&mut arms, variant_pat))
+            .map(|pat| make::match_arm(iter::once(pat), make::expr_empty_block()))
+            .collect()
+    } else {
+        return None;
+    };
 
     if missing_arms.is_empty() {
         return None;
@@ -104,8 +134,27 @@ fn resolve_enum_def(sema: &Semantics<RootDatabase>, expr: &ast::Expr) -> Option<
     })
 }
 
+fn resolve_tuple_of_enum_def(
+    sema: &Semantics<RootDatabase>,
+    expr: &ast::Expr,
+) -> Option<Vec<hir::Enum>> {
+    sema.type_of_expr(&expr)?
+        .tuple_fields(sema.db)
+        .iter()
+        .map(|ty| {
+            ty.autoderef(sema.db).find_map(|ty| match ty.as_adt() {
+                Some(Adt::Enum(e)) => Some(e),
+                // For now we only handle expansion for a tuple of enums. Here
+                // we map non-enum items to None and rely on `collect` to
+                // convert Vec<Option<hir::Enum>> into Option<Vec<hir::Enum>>.
+                _ => None,
+            })
+        })
+        .collect()
+}
+
 fn build_pat(db: &RootDatabase, module: hir::Module, var: hir::EnumVariant) -> Option<ast::Pat> {
-    let path = crate::ast_transform::path_to_ast(module.find_use_path(db, var.into())?);
+    let path = crate::ast_transform::path_to_ast(module.find_use_path(db, ModuleDef::from(var))?);
 
     // FIXME: use HIR for this; it doesn't currently expose struct vs. tuple vs. unit variants though
     let pat: ast::Pat = match var.source(db).value.kind() {
@@ -143,8 +192,23 @@ mod tests {
             fn main() {
                 match A::As<|> {
                     A::As,
-                    A::Bs{x,y:Some(_)} => (),
-                    A::Cs(_, Some(_)) => (),
+                    A::Bs{x,y:Some(_)} => {}
+                    A::Cs(_, Some(_)) => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn tuple_of_non_enum() {
+        // for now this case is not handled, although it potentially could be
+        // in the future
+        check_assist_not_applicable(
+            fill_match_arms,
+            r#"
+            fn main() {
+                match (0, false)<|> {
                 }
             }
             "#,
@@ -163,8 +227,8 @@ mod tests {
             }
             fn main() {
                 match A::As<|> {
-                    A::Bs{x,y:Some(_)} => (),
-                    A::Cs(_, Some(_)) => (),
+                    A::Bs{x,y:Some(_)} => {}
+                    A::Cs(_, Some(_)) => {}
                 }
             }
             "#,
@@ -176,9 +240,9 @@ mod tests {
             }
             fn main() {
                 match <|>A::As {
-                    A::Bs{x,y:Some(_)} => (),
-                    A::Cs(_, Some(_)) => (),
-                    A::As => (),
+                    A::Bs{x,y:Some(_)} => {}
+                    A::Cs(_, Some(_)) => {}
+                    A::As => {}
                 }
             }
             "#,
@@ -197,7 +261,7 @@ mod tests {
             }
             fn main() {
                 match A::As<|> {
-                    A::Cs(_) | A::Bs => (),
+                    A::Cs(_) | A::Bs => {}
                 }
             }
             "#,
@@ -209,8 +273,8 @@ mod tests {
             }
             fn main() {
                 match <|>A::As {
-                    A::Cs(_) | A::Bs => (),
-                    A::As => (),
+                    A::Cs(_) | A::Bs => {}
+                    A::As => {}
                 }
             }
             "#,
@@ -235,8 +299,8 @@ mod tests {
             }
             fn main() {
                 match A::As<|> {
-                    A::Bs if 0 < 1 => (),
-                    A::Ds(_value) => (),
+                    A::Bs if 0 < 1 => {}
+                    A::Ds(_value) => { let x = 1; }
                     A::Es(B::Xs) => (),
                 }
             }
@@ -255,11 +319,11 @@ mod tests {
             }
             fn main() {
                 match <|>A::As {
-                    A::Bs if 0 < 1 => (),
-                    A::Ds(_value) => (),
+                    A::Bs if 0 < 1 => {}
+                    A::Ds(_value) => { let x = 1; }
                     A::Es(B::Xs) => (),
-                    A::As => (),
-                    A::Cs => (),
+                    A::As => {}
+                    A::Cs => {}
                 }
             }
             "#,
@@ -296,11 +360,174 @@ mod tests {
             fn main() {
                 let a = A::As;
                 match <|>a {
-                    A::As => (),
-                    A::Bs => (),
-                    A::Cs(_) => (),
-                    A::Ds(_, _) => (),
-                    A::Es { x, y } => (),
+                    A::As => {}
+                    A::Bs => {}
+                    A::Cs(_) => {}
+                    A::Ds(_, _) => {}
+                    A::Es { x, y } => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_tuple_of_enum() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            enum B {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                let b = B::One;
+                match (a<|>, b) {}
+            }
+            "#,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            enum B {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                let b = B::One;
+                match <|>(a, b) {
+                    (A::One, B::One) => {}
+                    (A::One, B::Two) => {}
+                    (A::Two, B::One) => {}
+                    (A::Two, B::Two) => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_tuple_of_enum_ref() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            enum B {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                let b = B::One;
+                match (&a<|>, &b) {}
+            }
+            "#,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            enum B {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                let b = B::One;
+                match <|>(&a, &b) {
+                    (A::One, B::One) => {}
+                    (A::One, B::Two) => {}
+                    (A::Two, B::One) => {}
+                    (A::Two, B::Two) => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_tuple_of_enum_partial() {
+        check_assist_not_applicable(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            enum B {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                let b = B::One;
+                match (a<|>, b) {
+                    (A::Two, B::One) => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_tuple_of_enum_not_applicable() {
+        check_assist_not_applicable(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            enum B {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                let b = B::One;
+                match (a<|>, b) {
+                    (A::Two, B::One) => {}
+                    (A::One, B::One) => {}
+                    (A::One, B::Two) => {}
+                    (A::Two, B::Two) => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_single_element_tuple_of_enum() {
+        // For now we don't hande the case of a single element tuple, but
+        // we could handle this in the future if `make::tuple_pat` allowed
+        // creating a tuple with a single pattern.
+        check_assist_not_applicable(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+
+            fn main() {
+                let a = A::One;
+                match (a<|>, ) {
                 }
             }
             "#,
@@ -328,7 +555,7 @@ mod tests {
 
             fn foo(a: &A) {
                 match <|>a {
-                    A::As => (),
+                    A::As => {}
                 }
             }
             "#,
@@ -353,7 +580,7 @@ mod tests {
 
             fn foo(a: &mut A) {
                 match <|>a {
-                    A::Es { x, y } => (),
+                    A::Es { x, y } => {}
                 }
             }
             "#,
@@ -384,7 +611,7 @@ mod tests {
 
             fn main() {
                 match E::X {
-                    <|>_ => {},
+                    <|>_ => {}
                 }
             }
             "#,
@@ -393,8 +620,8 @@ mod tests {
 
             fn main() {
                 match <|>E::X {
-                    E::X => (),
-                    E::Y => (),
+                    E::X => {}
+                    E::Y => {}
                 }
             }
             "#,
@@ -421,8 +648,8 @@ mod tests {
 
             fn main() {
                 match <|>X {
-                    X => (),
-                    foo::E::Y => (),
+                    X => {}
+                    foo::E::Y => {}
                 }
             }
             "#,
diff --git a/crates/ra_assists/src/handlers/invert_if.rs b/crates/ra_assists/src/handlers/invert_if.rs
index 3a2665d17..4c5716868 100644
--- a/crates/ra_assists/src/handlers/invert_if.rs
+++ b/crates/ra_assists/src/handlers/invert_if.rs
@@ -33,6 +33,11 @@ pub(crate) fn invert_if(ctx: AssistCtx) -> Option<Assist> {
         return None;
     }
 
+    // This assist should not apply for if-let.
+    if expr.condition()?.pat().is_some() {
+        return None;
+    }
+
     let cond = expr.condition()?.expr()?;
     let then_node = expr.then_branch()?.syntax().clone();
 
@@ -90,4 +95,12 @@ mod tests {
     fn invert_if_doesnt_apply_with_cursor_not_on_if() {
         check_assist_not_applicable(invert_if, "fn f() { if !<|>cond { 3 * 2 } else { 1 } }")
     }
+
+    #[test]
+    fn invert_if_doesnt_apply_with_if_let() {
+        check_assist_not_applicable(
+            invert_if,
+            "fn f() { i<|>f let Some(_) = Some(1) { 1 } else { 0 } }",
+        )
+    }
 }
diff --git a/crates/ra_assists/src/handlers/merge_imports.rs b/crates/ra_assists/src/handlers/merge_imports.rs
index 89bc975bd..9c57d1e30 100644
--- a/crates/ra_assists/src/handlers/merge_imports.rs
+++ b/crates/ra_assists/src/handlers/merge_imports.rs
@@ -1,9 +1,9 @@
 use std::iter::successors;
 
 use ra_syntax::{
-    algo::neighbor,
+    algo::{neighbor, SyntaxRewriter},
     ast::{self, edit::AstNodeEdit, make},
-    AstNode, AstToken, Direction, InsertPosition, SyntaxElement, TextRange, T,
+    AstNode, Direction, InsertPosition, SyntaxElement, T,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -22,9 +22,10 @@ use crate::{Assist, AssistCtx, AssistId};
 // ```
 pub(crate) fn merge_imports(ctx: AssistCtx) -> Option<Assist> {
     let tree: ast::UseTree = ctx.find_node_at_offset()?;
-    let (new_tree, to_delete) = if let Some(use_item) =
-        tree.syntax().parent().and_then(ast::UseItem::cast)
-    {
+    let mut rewriter = SyntaxRewriter::default();
+    let mut offset = ctx.frange.range.start();
+
+    if let Some(use_item) = tree.syntax().parent().and_then(ast::UseItem::cast) {
         let (merged, to_delete) = next_prev()
             .filter_map(|dir| neighbor(&use_item, dir))
             .filter_map(|it| Some((it.clone(), it.use_tree()?)))
@@ -32,42 +33,28 @@ pub(crate) fn merge_imports(ctx: AssistCtx) -> Option<Assist> {
                 Some((try_merge_trees(&tree, &use_tree)?, use_item.clone()))
             })?;
 
-        let mut range = to_delete.syntax().text_range();
-        let next_ws = to_delete
-            .syntax()
-            .next_sibling_or_token()
-            .and_then(|it| it.into_token())
-            .and_then(ast::Whitespace::cast);
-        if let Some(ws) = next_ws {
-            range = range.extend_to(&ws.syntax().text_range())
+        rewriter.replace_ast(&tree, &merged);
+        rewriter += to_delete.remove();
+
+        if to_delete.syntax().text_range().end() < offset {
+            offset -= to_delete.syntax().text_range().len();
         }
-        (merged, range)
     } else {
         let (merged, to_delete) = next_prev()
             .filter_map(|dir| neighbor(&tree, dir))
             .find_map(|use_tree| Some((try_merge_trees(&tree, &use_tree)?, use_tree.clone())))?;
 
-        let mut range = to_delete.syntax().text_range();
-        if let Some((dir, nb)) = next_prev().find_map(|dir| Some((dir, neighbor(&to_delete, dir)?)))
-        {
-            let nb_range = nb.syntax().text_range();
-            if dir == Direction::Prev {
-                range = TextRange::from_to(nb_range.end(), range.end());
-            } else {
-                range = TextRange::from_to(range.start(), nb_range.start());
-            }
+        rewriter.replace_ast(&tree, &merged);
+        rewriter += to_delete.remove();
+
+        if to_delete.syntax().text_range().end() < offset {
+            offset -= to_delete.syntax().text_range().len();
         }
-        (merged, range)
     };
 
-    let mut offset = ctx.frange.range.start();
     ctx.add_assist(AssistId("merge_imports"), "Merge imports", |edit| {
-        edit.replace_ast(tree, new_tree);
-        edit.delete(to_delete);
-
-        if to_delete.end() <= offset {
-            offset -= to_delete.len();
-        }
+        edit.rewrite(rewriter);
+        // FIXME: we only need because our diff is imprecise
         edit.set_cursor(offset);
     })
 }
@@ -156,7 +143,7 @@ use std::fmt::Debug;
 use std::fmt<|>::Display;
 ",
             r"
-use std::fmt<|>::{Display, Debug};
+use std::fmt:<|>:{Display, Debug};
 ",
         );
     }
@@ -178,7 +165,57 @@ use std::{fmt<|>::{Debug, Display}};
 use std::{fmt::Debug, fmt<|>::Display};
 ",
             r"
-use std::{fmt<|>::{Display, Debug}};
+use std::{fmt::<|>{Display, Debug}};
+",
+        );
+    }
+
+    #[test]
+    fn removes_just_enough_whitespace() {
+        check_assist(
+            merge_imports,
+            r"
+use foo<|>::bar;
+use foo::baz;
+
+/// Doc comment
+",
+            r"
+use foo<|>::{bar, baz};
+
+/// Doc comment
+",
+        );
+    }
+
+    #[test]
+    fn works_with_trailing_comma() {
+        check_assist(
+            merge_imports,
+            r"
+use {
+    foo<|>::bar,
+    foo::baz,
+};
+",
+            r"
+use {
+    foo<|>::{bar, baz},
+};
+",
+        );
+        check_assist(
+            merge_imports,
+            r"
+use {
+    foo::baz,
+    foo<|>::bar,
+};
+",
+            r"
+use {
+    foo::{bar<|>, baz},
+};
 ",
         );
     }
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index b8704ea7d..bcc9b3f10 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -165,7 +165,6 @@ mod helpers {
 
     use ra_db::{fixture::WithFixture, FileId, FileRange, SourceDatabaseExt};
     use ra_ide_db::{symbol_index::SymbolsDatabase, RootDatabase};
-    use ra_syntax::TextRange;
     use test_utils::{add_cursor, assert_eq_text, extract_range_or_offset, RangeOrOffset};
 
     use crate::{AssistCtx, AssistHandler};
@@ -175,8 +174,7 @@ mod helpers {
         let (mut db, file_id) = RootDatabase::with_single_file(text);
         // FIXME: ideally, this should be done by the above `RootDatabase::with_single_file`,
         // but it looks like this might need specialization? :(
-        let local_roots = vec![db.file_source_root(file_id)];
-        db.set_local_roots(Arc::new(local_roots));
+        db.set_local_roots(Arc::new(vec![db.file_source_root(file_id)]));
         (db, file_id)
     }
 
@@ -206,11 +204,24 @@ mod helpers {
     }
 
     fn check(assist: AssistHandler, before: &str, expected: ExpectedResult) {
-        let (range_or_offset, before) = extract_range_or_offset(before);
-        let range: TextRange = range_or_offset.into();
+        let (text_without_caret, file_with_caret_id, range_or_offset, db) =
+            if before.contains("//-") {
+                let (mut db, position) = RootDatabase::with_position(before);
+                db.set_local_roots(Arc::new(vec![db.file_source_root(position.file_id)]));
+                (
+                    db.file_text(position.file_id).as_ref().to_owned(),
+                    position.file_id,
+                    RangeOrOffset::Offset(position.offset),
+                    db,
+                )
+            } else {
+                let (range_or_offset, text_without_caret) = extract_range_or_offset(before);
+                let (db, file_id) = with_single_file(&text_without_caret);
+                (text_without_caret, file_id, range_or_offset, db)
+            };
+
+        let frange = FileRange { file_id: file_with_caret_id, range: range_or_offset.into() };
 
-        let (db, file_id) = with_single_file(&before);
-        let frange = FileRange { file_id, range };
         let sema = Semantics::new(&db);
         let assist_ctx = AssistCtx::new(&sema, frange, true);
 
@@ -218,7 +229,7 @@ mod helpers {
             (Some(assist), ExpectedResult::After(after)) => {
                 let action = assist.0[0].action.clone().unwrap();
 
-                let mut actual = action.edit.apply(&before);
+                let mut actual = action.edit.apply(&text_without_caret);
                 match action.cursor_position {
                     None => {
                         if let RangeOrOffset::Offset(before_cursor_pos) = range_or_offset {
@@ -237,7 +248,7 @@ mod helpers {
             (Some(assist), ExpectedResult::Target(target)) => {
                 let action = assist.0[0].action.clone().unwrap();
                 let range = action.target.expect("expected target on action");
-                assert_eq_text!(&before[range], target);
+                assert_eq_text!(&text_without_caret[range], target);
             }
             (Some(_), ExpectedResult::NotApplicable) => panic!("assist should not be applicable!"),
             (None, ExpectedResult::After(_)) | (None, ExpectedResult::Target(_)) => {
diff --git a/crates/ra_cargo_watch/src/conv.rs b/crates/ra_cargo_watch/src/conv.rs
index c6f8ca329..817543deb 100644
--- a/crates/ra_cargo_watch/src/conv.rs
+++ b/crates/ra_cargo_watch/src/conv.rs
@@ -1,7 +1,8 @@
 //! This module provides the functionality needed to convert diagnostics from
 //! `cargo check` json format to the LSP diagnostic format.
 use cargo_metadata::diagnostic::{
-    Diagnostic as RustDiagnostic, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion,
+    Applicability, Diagnostic as RustDiagnostic, DiagnosticLevel, DiagnosticSpan,
+    DiagnosticSpanMacroExpansion,
 };
 use lsp_types::{
     CodeAction, Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag,
@@ -136,10 +137,13 @@ fn map_rust_child_diagnostic(
 
     let mut edit_map: HashMap<Url, Vec<TextEdit>> = HashMap::new();
     for &span in &spans {
-        if let Some(suggested_replacement) = &span.suggested_replacement {
-            let location = map_span_to_location(span, workspace_root);
-            let edit = TextEdit::new(location.range, suggested_replacement.clone());
-            edit_map.entry(location.uri).or_default().push(edit);
+        match (&span.suggestion_applicability, &span.suggested_replacement) {
+            (Some(Applicability::MachineApplicable), Some(suggested_replacement)) => {
+                let location = map_span_to_location(span, workspace_root);
+                let edit = TextEdit::new(location.range, suggested_replacement.clone());
+                edit_map.entry(location.uri).or_default().push(edit);
+            }
+            _ => {}
         }
     }
 
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
index 9e8f4eff4..a59fa84fa 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
@@ -58,44 +58,26 @@ expression: diag
                         },
                         message: "lint level defined here",
                     },
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: "file:///test/compiler/mir/tagset.rs",
+                            range: Range {
+                                start: Position {
+                                    line: 41,
+                                    character: 23,
+                                },
+                                end: Position {
+                                    line: 41,
+                                    character: 28,
+                                },
+                            },
+                        },
+                        message: "consider passing by value instead",
+                    },
                 ],
             ),
             tags: None,
         },
-        fixes: [
-            CodeAction {
-                title: "consider passing by value instead",
-                kind: Some(
-                    "quickfix",
-                ),
-                diagnostics: None,
-                edit: Some(
-                    WorkspaceEdit {
-                        changes: Some(
-                            {
-                                "file:///test/compiler/mir/tagset.rs": [
-                                    TextEdit {
-                                        range: Range {
-                                            start: Position {
-                                                line: 41,
-                                                character: 23,
-                                            },
-                                            end: Position {
-                                                line: 41,
-                                                character: 28,
-                                            },
-                                        },
-                                        new_text: "self",
-                                    },
-                                ],
-                            },
-                        ),
-                        document_changes: None,
-                    },
-                ),
-                command: None,
-                is_preferred: None,
-            },
-        ],
+        fixes: [],
     },
 ]
diff --git a/crates/ra_cargo_watch/src/lib.rs b/crates/ra_cargo_watch/src/lib.rs
index bffe5eb00..7c525c430 100644
--- a/crates/ra_cargo_watch/src/lib.rs
+++ b/crates/ra_cargo_watch/src/lib.rs
@@ -8,9 +8,10 @@ use lsp_types::{
     WorkDoneProgressEnd, WorkDoneProgressReport,
 };
 use std::{
+    error, fmt,
     io::{BufRead, BufReader},
     path::{Path, PathBuf},
-    process::{Child, Command, Stdio},
+    process::{Command, Stdio},
     thread::JoinHandle,
     time::Instant,
 };
@@ -70,10 +71,10 @@ 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 recv = self.cmd_send.take();
+            let cmd_send = self.cmd_send.take();
 
             // Dropping the sender finishes the thread loop
-            drop(recv);
+            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
@@ -246,11 +247,21 @@ enum CheckEvent {
     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,
-) -> Child {
+) -> Result<(), CargoError> {
     let mut command = Command::new("cargo");
     if let Some(current_dir) = current_dir {
         command.current_dir(current_dir);
@@ -273,6 +284,8 @@ pub fn run_cargo(
     // 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,
@@ -291,12 +304,31 @@ pub fn run_cargo(
             }
         };
 
+        read_at_least_one_message = true;
+
         if !on_message(message) {
             break;
         }
     }
 
-    child
+    // 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 {
@@ -325,7 +357,7 @@ impl WatchThread {
                 // which will break out of the loop, and continue the shutdown
                 let _ = message_send.send(CheckEvent::Begin);
 
-                let mut child = run_cargo(&args, Some(&workspace_root), &mut |message| {
+                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,
@@ -334,26 +366,19 @@ impl WatchThread {
                         _ => {}
                     }
 
-                    match message_send.send(CheckEvent::Msg(message)) {
-                        Ok(()) => {}
-                        Err(_err) => {
-                            // The send channel was closed, so we want to shutdown
-                            return false;
-                        }
-                    };
-
-                    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);
-
-                // It is okay to ignore the result, as it only errors if the process is already dead
-                let _ = child.kill();
-
-                // Again, we don't care about the exit status so just ignore the result
-                let _ = child.wait();
             }))
         } else {
             None
diff --git a/crates/ra_fmt/Cargo.toml b/crates/ra_fmt/Cargo.toml
index ea9befeaf..e9d057afc 100644
--- a/crates/ra_fmt/Cargo.toml
+++ b/crates/ra_fmt/Cargo.toml
@@ -9,6 +9,6 @@ publish = false
 doctest = false
 
 [dependencies]
-itertools = "0.8.2"
+itertools = "0.9.0"
 
 ra_syntax = { path = "../ra_syntax" }
diff --git a/crates/ra_hir/Cargo.toml b/crates/ra_hir/Cargo.toml
index 42193b492..ba7b39a19 100644
--- a/crates/ra_hir/Cargo.toml
+++ b/crates/ra_hir/Cargo.toml
@@ -13,7 +13,7 @@ rustc-hash = "1.1.0"
 either = "1.5.3"
 arrayvec = "0.5.1"
 
-itertools = "0.8.2"
+itertools = "0.9.0"
 
 ra_syntax = { path = "../ra_syntax" }
 ra_db = { path = "../ra_db" }
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 45e31095c..c5cfd875f 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -10,7 +10,7 @@ use hir_def::{
     docs::Documentation,
     expr::{BindingAnnotation, Pat, PatId},
     per_ns::PerNs,
-    resolver::HasResolver,
+    resolver::{HasResolver, Resolver},
     type_ref::{Mutability, TypeRef},
     AdtId, AssocContainerId, ConstId, DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule,
     ImplId, LocalEnumVariantId, LocalModuleId, LocalStructFieldId, Lookup, ModuleId, StaticId,
@@ -33,7 +33,11 @@ use ra_syntax::{
 };
 use rustc_hash::FxHashSet;
 
-use crate::{db::HirDatabase, has_source::HasSource, CallableDef, HirDisplay, InFile, Name};
+use crate::{
+    db::{DefDatabase, HirDatabase},
+    has_source::HasSource,
+    CallableDef, HirDisplay, InFile, Name,
+};
 
 /// hir::Crate describes a single crate. It's the main interface with which
 /// a crate's dependencies interact. Mostly, it should be just a proxy for the
@@ -274,20 +278,10 @@ impl Module {
     /// this module, if possible.
     pub fn find_use_path(
         self,
-        db: &dyn HirDatabase,
-        item: ModuleDef,
+        db: &dyn DefDatabase,
+        item: impl Into<ItemInNs>,
     ) -> Option<hir_def::path::ModPath> {
-        // FIXME expose namespace choice
-        hir_def::find_path::find_path(db.upcast(), determine_item_namespace(item), self.into())
-    }
-}
-
-fn determine_item_namespace(module_def: ModuleDef) -> ItemInNs {
-    match module_def {
-        ModuleDef::Static(_) | ModuleDef::Const(_) | ModuleDef::Function(_) => {
-            ItemInNs::Values(module_def.into())
-        }
-        _ => ItemInNs::Types(module_def.into()),
+        hir_def::find_path::find_path(db, item.into(), self.into())
     }
 }
 
@@ -912,10 +906,8 @@ impl Local {
         let def = DefWithBodyId::from(self.parent);
         let infer = db.infer(def);
         let ty = infer[self.pat_id].clone();
-        let resolver = def.resolver(db.upcast());
         let krate = def.module(db.upcast()).krate;
-        let environment = TraitEnvironment::lower(db, &resolver);
-        Type { krate, ty: InEnvironment { value: ty, environment } }
+        Type::new(db, krate, def, ty)
     }
 
     pub fn source(self, db: &dyn HirDatabase) -> InFile<Either<ast::BindPat, ast::SelfParam>> {
@@ -1020,11 +1012,21 @@ impl ImplDef {
 
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct Type {
-    pub(crate) krate: CrateId,
-    pub(crate) ty: InEnvironment<Ty>,
+    krate: CrateId,
+    ty: InEnvironment<Ty>,
 }
 
 impl Type {
+    pub(crate) fn new_with_resolver(
+        db: &dyn HirDatabase,
+        resolver: &Resolver,
+        ty: Ty,
+    ) -> Option<Type> {
+        let krate = resolver.krate()?;
+        let environment = TraitEnvironment::lower(db, &resolver);
+        Some(Type { krate, ty: InEnvironment { value: ty, environment } })
+    }
+
     fn new(db: &dyn HirDatabase, krate: CrateId, lexical_env: impl HasResolver, ty: Ty) -> Type {
         let resolver = lexical_env.resolver(db.upcast());
         let environment = TraitEnvironment::lower(db, &resolver);
@@ -1042,30 +1044,18 @@ impl Type {
     }
 
     pub fn is_bool(&self) -> bool {
-        match &self.ty.value {
-            Ty::Apply(a_ty) => match a_ty.ctor {
-                TypeCtor::Bool => true,
-                _ => false,
-            },
-            _ => false,
-        }
+        matches!(self.ty.value, Ty::Apply(ApplicationTy { ctor: TypeCtor::Bool, .. }))
     }
 
     pub fn is_mutable_reference(&self) -> bool {
-        match &self.ty.value {
-            Ty::Apply(a_ty) => match a_ty.ctor {
-                TypeCtor::Ref(Mutability::Mut) => true,
-                _ => false,
-            },
-            _ => false,
-        }
+        matches!(
+            self.ty.value,
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Ref(Mutability::Mut), .. })
+        )
     }
 
     pub fn is_unknown(&self) -> bool {
-        match &self.ty.value {
-            Ty::Unknown => true,
-            _ => false,
-        }
+        matches!(self.ty.value, Ty::Unknown)
     }
 
     /// Checks that particular type `ty` implements `std::future::Future`.
diff --git a/crates/ra_hir/src/from_id.rs b/crates/ra_hir/src/from_id.rs
index c179b13c6..62fb52e72 100644
--- a/crates/ra_hir/src/from_id.rs
+++ b/crates/ra_hir/src/from_id.rs
@@ -9,8 +9,8 @@ use hir_def::{
 };
 
 use crate::{
-    Adt, AssocItem, AttrDef, DefWithBody, EnumVariant, GenericDef, Local, ModuleDef, StructField,
-    VariantDef,
+    code_model::ItemInNs, Adt, AssocItem, AttrDef, DefWithBody, EnumVariant, GenericDef, Local,
+    MacroDef, ModuleDef, StructField, VariantDef,
 };
 
 macro_rules! from_id {
@@ -228,3 +228,20 @@ impl From<(DefWithBodyId, PatId)> for Local {
         Local { parent, pat_id }
     }
 }
+
+impl From<MacroDef> for ItemInNs {
+    fn from(macro_def: MacroDef) -> Self {
+        ItemInNs::Macros(macro_def.into())
+    }
+}
+
+impl From<ModuleDef> for ItemInNs {
+    fn from(module_def: ModuleDef) -> Self {
+        match module_def {
+            ModuleDef::Static(_) | ModuleDef::Const(_) | ModuleDef::Function(_) => {
+                ItemInNs::Values(module_def.into())
+            }
+            _ => ItemInNs::Types(module_def.into()),
+        }
+    }
+}
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 9f59d590c..713d45f48 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -4,6 +4,18 @@
 //! The principal difference between HIR and syntax trees is that HIR is bound
 //! to a particular crate instance. That is, it has cfg flags and features
 //! applied. So, the relation between syntax and HIR is many-to-one.
+//!
+//! HIR is the public API of the all of the compiler logic above syntax trees.
+//! It is written in "OO" style. Each type is self contained (as in, it knows it's
+//! parents and full context). It should be "clean code".
+//!
+//! `ra_hir_*` crates are the implementation of the compiler logic.
+//! They are written in "ECS" style, with relatively little abstractions.
+//! Many types are not self-contained, and explicitly use local indexes, arenas, etc.
+//!
+//! `ra_hir` is what insulates the "we don't know how to actually write an incremental compiler"
+//! from the ide with completions, hovers, etc. It is a (soft, internal) boundary:
+//! https://www.tedinski.com/2018/02/06/system-boundaries.html.
 
 #![recursion_limit = "512"]
 
diff --git a/crates/ra_hir/src/semantics.rs b/crates/ra_hir/src/semantics.rs
index 55e634528..d982f6ffa 100644
--- a/crates/ra_hir/src/semantics.rs
+++ b/crates/ra_hir/src/semantics.rs
@@ -12,7 +12,8 @@ use hir_expand::ExpansionInfo;
 use ra_db::{FileId, FileRange};
 use ra_prof::profile;
 use ra_syntax::{
-    algo::skip_trivia_token, ast, AstNode, Direction, SyntaxNode, SyntaxToken, TextRange, TextUnit,
+    algo::{find_node_at_offset, skip_trivia_token},
+    ast, AstNode, Direction, SyntaxNode, SyntaxToken, TextRange, TextUnit,
 };
 use rustc_hash::{FxHashMap, FxHashSet};
 
@@ -108,6 +109,17 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         token.value
     }
 
+    pub fn descend_node_at_offset<N: ast::AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextUnit,
+    ) -> Option<N> {
+        // Handle macro token cases
+        node.token_at_offset(offset)
+            .map(|token| self.descend_into_macros(token))
+            .find_map(|it| self.ancestors_with_macros(it.parent()).find_map(N::cast))
+    }
+
     pub fn original_range(&self, node: &SyntaxNode) -> FileRange {
         let node = self.find_file(node.clone());
         original_range(self.db, node.as_ref())
@@ -129,6 +141,8 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
             .kmerge_by(|node1, node2| node1.text_range().len() < node2.text_range().len())
     }
 
+    /// Find a AstNode by offset inside SyntaxNode, if it is inside *Macrofile*,
+    /// search up until it is of the target AstNode type
     pub fn find_node_at_offset_with_macros<N: AstNode>(
         &self,
         node: &SyntaxNode,
@@ -137,6 +151,19 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.ancestors_at_offset_with_macros(node, offset).find_map(N::cast)
     }
 
+    /// Find a AstNode by offset inside SyntaxNode, if it is inside *MacroCall*,
+    /// descend it and find again
+    pub fn find_node_at_offset_with_descend<N: AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextUnit,
+    ) -> Option<N> {
+        if let Some(it) = find_node_at_offset(&node, offset) {
+            return Some(it);
+        }
+        self.descend_node_at_offset(&node, offset)
+    }
+
     pub fn type_of_expr(&self, expr: &ast::Expr) -> Option<Type> {
         self.analyze(expr.syntax()).type_of(self.db, &expr)
     }
diff --git a/crates/ra_hir/src/source_analyzer.rs b/crates/ra_hir/src/source_analyzer.rs
index e8afef328..10c12c910 100644
--- a/crates/ra_hir/src/source_analyzer.rs
+++ b/crates/ra_hir/src/source_analyzer.rs
@@ -17,7 +17,7 @@ use hir_def::{
     AsMacroCall, DefWithBodyId,
 };
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
-use hir_ty::{InEnvironment, InferenceResult, TraitEnvironment};
+use hir_ty::InferenceResult;
 use ra_syntax::{
     ast::{self, AstNode},
     SyntaxNode, SyntaxNodePtr, TextUnit,
@@ -103,10 +103,6 @@ impl SourceAnalyzer {
         Some(res)
     }
 
-    fn trait_env(&self, db: &dyn HirDatabase) -> Arc<TraitEnvironment> {
-        TraitEnvironment::lower(db, &self.resolver)
-    }
-
     pub(crate) fn type_of(&self, db: &dyn HirDatabase, expr: &ast::Expr) -> Option<Type> {
         let expr_id = match expr {
             ast::Expr::MacroCall(call) => {
@@ -117,15 +113,13 @@ impl SourceAnalyzer {
         }?;
 
         let ty = self.infer.as_ref()?[expr_id].clone();
-        let environment = self.trait_env(db);
-        Some(Type { krate: self.resolver.krate()?, ty: InEnvironment { value: ty, environment } })
+        Type::new_with_resolver(db, &self.resolver, ty)
     }
 
     pub(crate) fn type_of_pat(&self, db: &dyn HirDatabase, pat: &ast::Pat) -> Option<Type> {
         let pat_id = self.pat_id(pat)?;
         let ty = self.infer.as_ref()?[pat_id].clone();
-        let environment = self.trait_env(db);
-        Some(Type { krate: self.resolver.krate()?, ty: InEnvironment { value: ty, environment } })
+        Type::new_with_resolver(db, &self.resolver, ty)
     }
 
     pub(crate) fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
diff --git a/crates/ra_hir_def/src/body.rs b/crates/ra_hir_def/src/body.rs
index 27a297e8b..5f9d53ecb 100644
--- a/crates/ra_hir_def/src/body.rs
+++ b/crates/ra_hir_def/src/body.rs
@@ -30,6 +30,7 @@ pub(crate) struct Expander {
     hygiene: Hygiene,
     ast_id_map: Arc<AstIdMap>,
     module: ModuleId,
+    recursive_limit: usize,
 }
 
 impl Expander {
@@ -41,7 +42,7 @@ impl Expander {
         let crate_def_map = db.crate_def_map(module.krate);
         let hygiene = Hygiene::new(db.upcast(), current_file_id);
         let ast_id_map = db.ast_id_map(current_file_id);
-        Expander { crate_def_map, current_file_id, hygiene, ast_id_map, module }
+        Expander { crate_def_map, current_file_id, hygiene, ast_id_map, module, recursive_limit: 0 }
     }
 
     pub(crate) fn enter_expand<T: ast::AstNode>(
@@ -50,6 +51,10 @@ impl Expander {
         local_scope: Option<&ItemScope>,
         macro_call: ast::MacroCall,
     ) -> Option<(Mark, T)> {
+        if self.recursive_limit > 1024 {
+            return None;
+        }
+
         let macro_call = InFile::new(self.current_file_id, &macro_call);
 
         if let Some(call_id) = macro_call.as_call_id(db, |path| {
@@ -73,6 +78,7 @@ impl Expander {
                     self.hygiene = Hygiene::new(db.upcast(), file_id);
                     self.current_file_id = file_id;
                     self.ast_id_map = db.ast_id_map(file_id);
+                    self.recursive_limit += 1;
 
                     return Some((mark, expr));
                 }
@@ -88,6 +94,7 @@ impl Expander {
         self.hygiene = Hygiene::new(db.upcast(), mark.file_id);
         self.current_file_id = mark.file_id;
         self.ast_id_map = mem::take(&mut mark.ast_id_map);
+        self.recursive_limit -= 1;
         mark.bomb.defuse();
     }
 
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index e8c58ed32..3cf0c66ea 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -453,7 +453,7 @@ impl ExprCollector<'_> {
                 }
             }
             ast::Expr::MacroCall(e) => {
-                if let Some(name) = is_macro_rules(&e) {
+                if let Some(name) = e.is_macro_rules().map(|it| it.as_name()) {
                     let mac = MacroDefId {
                         krate: Some(self.expander.module.krate),
                         ast_id: Some(self.expander.ast_id(&e)),
@@ -697,16 +697,6 @@ impl ExprCollector<'_> {
     }
 }
 
-fn is_macro_rules(m: &ast::MacroCall) -> Option<Name> {
-    let name = m.path()?.segment()?.name_ref()?.as_name();
-
-    if name == name![macro_rules] {
-        Some(m.name()?.as_name())
-    } else {
-        None
-    }
-}
-
 impl From<ast::BinOp> for BinaryOp {
     fn from(ast_op: ast::BinOp) -> Self {
         match ast_op {
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index 246032c13..904080341 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -95,7 +95,7 @@ pub struct Path {
     /// Note that paths like `<Type as Trait>::foo` are desugard to `Trait::<Self=Type>::foo`.
     type_anchor: Option<Box<TypeRef>>,
     mod_path: ModPath,
-    /// Invariant: the same len as self.path.segments
+    /// Invariant: the same len as `self.mod_path.segments`
     generic_args: Vec<Option<Arc<GenericArgs>>>,
 }
 
diff --git a/crates/ra_hir_expand/src/db.rs b/crates/ra_hir_expand/src/db.rs
index d171d2dfd..5a696542f 100644
--- a/crates/ra_hir_expand/src/db.rs
+++ b/crates/ra_hir_expand/src/db.rs
@@ -6,7 +6,7 @@ use mbe::{ExpandResult, MacroRules};
 use ra_db::{salsa, SourceDatabase};
 use ra_parser::FragmentKind;
 use ra_prof::profile;
-use ra_syntax::{AstNode, Parse, SyntaxKind::*, SyntaxNode};
+use ra_syntax::{algo::diff, AstNode, Parse, SyntaxKind::*, SyntaxNode};
 
 use crate::{
     ast_id_map::AstIdMap, BuiltinDeriveExpander, BuiltinFnLikeExpander, EagerCallLoc, EagerMacroId,
@@ -238,7 +238,7 @@ pub fn parse_macro_with_arg(
     } else {
         db.macro_expand(macro_call_id)
     };
-    if let Some(err) = err {
+    if let Some(err) = &err {
         // Note:
         // The final goal we would like to make all parse_macro success,
         // such that the following log will not call anyway.
@@ -272,7 +272,25 @@ pub fn parse_macro_with_arg(
     let fragment_kind = to_fragment_kind(db, macro_call_id);
 
     let (parse, rev_token_map) = mbe::token_tree_to_syntax_node(&tt, fragment_kind).ok()?;
-    Some((parse, Arc::new(rev_token_map)))
+
+    if err.is_none() {
+        Some((parse, Arc::new(rev_token_map)))
+    } else {
+        // FIXME:
+        // In future, we should propagate the actual error with recovery information
+        // instead of ignore the error here.
+
+        // Safe check for recurisve identity macro
+        let node = parse.syntax_node();
+        let file: HirFileId = macro_file.into();
+        let call_node = file.call_node(db)?;
+
+        if !diff(&node, &call_node.value).is_empty() {
+            Some((parse, Arc::new(rev_token_map)))
+        } else {
+            None
+        }
+    }
 }
 
 /// Given a `MacroCallId`, return what `FragmentKind` it belongs to.
diff --git a/crates/ra_hir_expand/src/eager.rs b/crates/ra_hir_expand/src/eager.rs
index 4cbce4df5..687d40294 100644
--- a/crates/ra_hir_expand/src/eager.rs
+++ b/crates/ra_hir_expand/src/eager.rs
@@ -26,8 +26,8 @@ use crate::{
 };
 
 use ra_parser::FragmentKind;
-use ra_syntax::{algo::replace_descendants, SyntaxElement, SyntaxNode};
-use std::{collections::HashMap, sync::Arc};
+use ra_syntax::{algo::SyntaxRewriter, SyntaxNode};
+use std::sync::Arc;
 
 pub fn expand_eager_macro(
     db: &dyn AstDatabase,
@@ -95,10 +95,10 @@ fn eager_macro_recur(
     curr: InFile<SyntaxNode>,
     macro_resolver: &dyn Fn(ast::Path) -> Option<MacroDefId>,
 ) -> Option<SyntaxNode> {
-    let mut original = curr.value.clone();
+    let original = curr.value.clone();
 
     let children = curr.value.descendants().filter_map(ast::MacroCall::cast);
-    let mut replaces: HashMap<SyntaxElement, SyntaxElement> = HashMap::default();
+    let mut rewriter = SyntaxRewriter::default();
 
     // Collect replacement
     for child in children {
@@ -119,12 +119,9 @@ fn eager_macro_recur(
             }
         };
 
-        replaces.insert(child.syntax().clone().into(), insert.into());
+        rewriter.replace(child.syntax(), &insert);
     }
 
-    if !replaces.is_empty() {
-        original = replace_descendants(&original, |n| replaces.get(n).cloned());
-    }
-
-    Some(original)
+    let res = rewriter.rewrite(&original);
+    Some(res)
 }
diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index 69c059ac8..533c6ccfb 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -95,14 +95,14 @@ impl Ty {
         // Types like slice can have inherent impls in several crates, (core and alloc).
         // The corresponding impls are marked with lang items, so we can use them to find the required crates.
         macro_rules! lang_item_crate {
-        ($($name:expr),+ $(,)?) => {{
-            let mut v = ArrayVec::<[LangItemTarget; 2]>::new();
-            $(
-                v.extend(db.lang_item(cur_crate, $name.into()));
-            )+
-            v
-        }};
-    }
+            ($($name:expr),+ $(,)?) => {{
+                let mut v = ArrayVec::<[LangItemTarget; 2]>::new();
+                $(
+                    v.extend(db.lang_item(cur_crate, $name.into()));
+                )+
+                v
+            }};
+        }
 
         let lang_item_targets = match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index 14c8ed3a9..a02e3ee05 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -453,3 +453,34 @@ pub mod str {
     // should be Option<char>, but currently not because of Chalk ambiguity problem
     assert_eq!("(Option<{unknown}>, Option<{unknown}>)", super::type_at_pos(&db, pos));
 }
+
+#[test]
+fn issue_3642_bad_macro_stackover() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs
+#[macro_export]
+macro_rules! match_ast {
+    (match $node:ident { $($tt:tt)* }) => { match_ast!(match ($node) { $($tt)* }) };
+
+    (match ($node:expr) {
+        $( ast::$ast:ident($it:ident) => $res:expr, )*
+        _ => $catch_all:expr $(,)?
+    }) => {{
+        $( if let Some($it) = ast::$ast::cast($node.clone()) { $res } else )*
+        { $catch_all }
+    }};
+}
+
+fn main() {
+    let anchor<|> = match_ast! {
+        match parent {
+            as => {},
+            _ => return None
+        }
+    };
+}"#,
+    );
+
+    assert_eq!("()", super::type_at_pos(&db, pos));
+}
diff --git a/crates/ra_ide/Cargo.toml b/crates/ra_ide/Cargo.toml
index 7235c944c..36eec0e60 100644
--- a/crates/ra_ide/Cargo.toml
+++ b/crates/ra_ide/Cargo.toml
@@ -14,7 +14,7 @@ wasm = []
 either = "1.5.3"
 format-buf = "1.0.0"
 indexmap = "1.3.2"
-itertools = "0.8.2"
+itertools = "0.9.0"
 join_to_string = "0.1.3"
 log = "0.4.8"
 rustc-hash = "1.1.0"
diff --git a/crates/ra_ide/src/completion/complete_postfix.rs b/crates/ra_ide/src/completion/complete_postfix.rs
index 0ba382165..0a00054b2 100644
--- a/crates/ra_ide/src/completion/complete_postfix.rs
+++ b/crates/ra_ide/src/completion/complete_postfix.rs
@@ -1,6 +1,9 @@
 //! FIXME: write short doc here
 
-use ra_syntax::{ast::AstNode, TextRange, TextUnit};
+use ra_syntax::{
+    ast::{self, AstNode},
+    TextRange, TextUnit,
+};
 use ra_text_edit::TextEdit;
 
 use crate::{
@@ -21,13 +24,8 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
         None => return,
     };
 
-    let receiver_text = if ctx.dot_receiver_is_ambiguous_float_literal {
-        let text = dot_receiver.syntax().text();
-        let without_dot = ..text.len() - TextUnit::of_char('.');
-        text.slice(without_dot).to_string()
-    } else {
-        dot_receiver.syntax().text().to_string()
-    };
+    let receiver_text =
+        get_receiver_text(dot_receiver, ctx.dot_receiver_is_ambiguous_float_literal);
 
     let receiver_ty = match ctx.sema.type_of_expr(&dot_receiver) {
         Some(it) => it,
@@ -35,10 +33,17 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
     };
 
     if receiver_ty.is_bool() || receiver_ty.is_unknown() {
-        postfix_snippet(ctx, "if", "if expr {}", &format!("if {} {{$0}}", receiver_text))
-            .add_to(acc);
         postfix_snippet(
             ctx,
+            &dot_receiver,
+            "if",
+            "if expr {}",
+            &format!("if {} {{$0}}", receiver_text),
+        )
+        .add_to(acc);
+        postfix_snippet(
+            ctx,
+            &dot_receiver,
             "while",
             "while expr {}",
             &format!("while {} {{\n$0\n}}", receiver_text),
@@ -46,28 +51,70 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
         .add_to(acc);
     }
 
-    postfix_snippet(ctx, "not", "!expr", &format!("!{}", receiver_text)).add_to(acc);
+    // !&&&42 is a compiler error, ergo process it before considering the references
+    postfix_snippet(ctx, &dot_receiver, "not", "!expr", &format!("!{}", receiver_text)).add_to(acc);
 
-    postfix_snippet(ctx, "ref", "&expr", &format!("&{}", receiver_text)).add_to(acc);
-    postfix_snippet(ctx, "refm", "&mut expr", &format!("&mut {}", receiver_text)).add_to(acc);
+    postfix_snippet(ctx, &dot_receiver, "ref", "&expr", &format!("&{}", receiver_text)).add_to(acc);
+    postfix_snippet(ctx, &dot_receiver, "refm", "&mut expr", &format!("&mut {}", receiver_text))
+        .add_to(acc);
+
+    // The rest of the postfix completions create an expression that moves an argument,
+    // so it's better to consider references now to avoid breaking the compilation
+    let dot_receiver = include_references(dot_receiver);
+    let receiver_text =
+        get_receiver_text(&dot_receiver, ctx.dot_receiver_is_ambiguous_float_literal);
 
     postfix_snippet(
         ctx,
+        &dot_receiver,
         "match",
         "match expr {}",
         &format!("match {} {{\n    ${{1:_}} => {{$0\\}},\n}}", receiver_text),
     )
     .add_to(acc);
 
-    postfix_snippet(ctx, "dbg", "dbg!(expr)", &format!("dbg!({})", receiver_text)).add_to(acc);
+    postfix_snippet(
+        ctx,
+        &dot_receiver,
+        "box",
+        "Box::new(expr)",
+        &format!("Box::new({})", receiver_text),
+    )
+    .add_to(acc);
 
-    postfix_snippet(ctx, "box", "Box::new(expr)", &format!("Box::new({})", receiver_text))
+    postfix_snippet(ctx, &dot_receiver, "dbg", "dbg!(expr)", &format!("dbg!({})", receiver_text))
         .add_to(acc);
 }
 
-fn postfix_snippet(ctx: &CompletionContext, label: &str, detail: &str, snippet: &str) -> Builder {
+fn get_receiver_text(receiver: &ast::Expr, receiver_is_ambiguous_float_literal: bool) -> String {
+    if receiver_is_ambiguous_float_literal {
+        let text = receiver.syntax().text();
+        let without_dot = ..text.len() - TextUnit::of_char('.');
+        text.slice(without_dot).to_string()
+    } else {
+        receiver.to_string()
+    }
+}
+
+fn include_references(initial_element: &ast::Expr) -> ast::Expr {
+    let mut resulting_element = initial_element.clone();
+    while let Some(parent_ref_element) =
+        resulting_element.syntax().parent().and_then(ast::RefExpr::cast)
+    {
+        resulting_element = ast::Expr::from(parent_ref_element);
+    }
+    resulting_element
+}
+
+fn postfix_snippet(
+    ctx: &CompletionContext,
+    receiver: &ast::Expr,
+    label: &str,
+    detail: &str,
+    snippet: &str,
+) -> Builder {
     let edit = {
-        let receiver_syntax = ctx.dot_receiver.as_ref().expect("no receiver available").syntax();
+        let receiver_syntax = receiver.syntax();
         let receiver_range = ctx.sema.original_range(receiver_syntax).range;
         let delete_range = TextRange::from_to(receiver_range.start(), ctx.source_range().end());
         TextEdit::replace(delete_range, snippet.to_string())
@@ -340,4 +387,63 @@ mod tests {
         "###
         );
     }
+
+    #[test]
+    fn postfix_completion_for_references() {
+        assert_debug_snapshot!(
+            do_postfix_completion(
+                r#"
+                fn main() {
+                    &&&&42.<|>
+                }
+                "#,
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "box",
+                source_range: [56; 56),
+                delete: [49; 56),
+                insert: "Box::new(&&&&42)",
+                detail: "Box::new(expr)",
+            },
+            CompletionItem {
+                label: "dbg",
+                source_range: [56; 56),
+                delete: [49; 56),
+                insert: "dbg!(&&&&42)",
+                detail: "dbg!(expr)",
+            },
+            CompletionItem {
+                label: "match",
+                source_range: [56; 56),
+                delete: [49; 56),
+                insert: "match &&&&42 {\n    ${1:_} => {$0\\},\n}",
+                detail: "match expr {}",
+            },
+            CompletionItem {
+                label: "not",
+                source_range: [56; 56),
+                delete: [53; 56),
+                insert: "!42",
+                detail: "!expr",
+            },
+            CompletionItem {
+                label: "ref",
+                source_range: [56; 56),
+                delete: [53; 56),
+                insert: "&42",
+                detail: "&expr",
+            },
+            CompletionItem {
+                label: "refm",
+                source_range: [56; 56),
+                delete: [53; 56),
+                insert: "&mut 42",
+                detail: "&mut expr",
+            },
+        ]
+        "###
+        );
+    }
 }
diff --git a/crates/ra_ide/src/completion/complete_record_literal.rs b/crates/ra_ide/src/completion/complete_record_literal.rs
index 83ed1d52c..e4e764f58 100644
--- a/crates/ra_ide/src/completion/complete_record_literal.rs
+++ b/crates/ra_ide/src/completion/complete_record_literal.rs
@@ -1,6 +1,7 @@
 //! 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) {
@@ -11,8 +12,24 @@ pub(super) fn complete_record_literal(acc: &mut Completions, ctx: &CompletionCon
         _ => 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) {
-        acc.add_field(ctx, field, &field_ty);
+        if !already_present_names.contains(&SmolStr::from(field.name(ctx.db).to_string())) {
+            acc.add_field(ctx, field, &field_ty);
+        }
     }
 }
 
@@ -178,4 +195,47 @@ mod tests {
         ]
         "###);
     }
+
+    #[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_trait_impl.rs b/crates/ra_ide/src/completion/complete_trait_impl.rs
index 7fefa2c7a..ded1ff3bc 100644
--- a/crates/ra_ide/src/completion/complete_trait_impl.rs
+++ b/crates/ra_ide/src/completion/complete_trait_impl.rs
@@ -193,7 +193,7 @@ fn add_const_impl(
 }
 
 fn make_const_compl_syntax(const_: &ast::ConstDef) -> String {
-    let const_ = edit::strip_attrs_and_docs(const_);
+    let const_ = edit::remove_attrs_and_docs(const_);
 
     let const_start = const_.syntax().text_range().start();
     let const_end = const_.syntax().text_range().end();
diff --git a/crates/ra_ide/src/expand_macro.rs b/crates/ra_ide/src/expand_macro.rs
index e58526f31..f536ba3e7 100644
--- a/crates/ra_ide/src/expand_macro.rs
+++ b/crates/ra_ide/src/expand_macro.rs
@@ -3,10 +3,9 @@
 use hir::Semantics;
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
-    algo::{find_node_at_offset, replace_descendants},
-    ast, AstNode, NodeOrToken, SyntaxElement, SyntaxKind, SyntaxNode, WalkEvent, T,
+    algo::{find_node_at_offset, SyntaxRewriter},
+    ast, AstNode, NodeOrToken, SyntaxKind, SyntaxNode, WalkEvent, T,
 };
-use rustc_hash::FxHashMap;
 
 use crate::FilePosition;
 
@@ -37,7 +36,7 @@ fn expand_macro_recur(
     let mut expanded = sema.expand(macro_call)?;
 
     let children = expanded.descendants().filter_map(ast::MacroCall::cast);
-    let mut replaces: FxHashMap<SyntaxElement, SyntaxElement> = FxHashMap::default();
+    let mut rewriter = SyntaxRewriter::default();
 
     for child in children.into_iter() {
         if let Some(new_node) = expand_macro_recur(sema, &child) {
@@ -47,12 +46,13 @@ fn expand_macro_recur(
             if expanded == *child.syntax() {
                 expanded = new_node;
             } else {
-                replaces.insert(child.syntax().clone().into(), new_node.into());
+                rewriter.replace(child.syntax(), &new_node)
             }
         }
     }
 
-    Some(replace_descendants(&expanded, |n| replaces.get(n).cloned()))
+    let res = rewriter.rewrite(&expanded);
+    Some(res)
 }
 
 // FIXME: It would also be cool to share logic here and in the mbe tests,
diff --git a/crates/ra_ide/src/references.rs b/crates/ra_ide/src/references.rs
index 3ea0ac230..746cc86ba 100644
--- a/crates/ra_ide/src/references.rs
+++ b/crates/ra_ide/src/references.rs
@@ -94,12 +94,16 @@ pub(crate) fn find_all_refs(
     let sema = Semantics::new(db);
     let syntax = sema.parse(position.file_id).syntax().clone();
 
-    let (opt_name, search_kind) =
-        if let Some(name) = get_struct_def_name_for_struct_literal_search(&syntax, position) {
-            (Some(name), ReferenceKind::StructLiteral)
-        } else {
-            (find_node_at_offset::<ast::Name>(&syntax, position.offset), ReferenceKind::Other)
-        };
+    let (opt_name, search_kind) = if let Some(name) =
+        get_struct_def_name_for_struct_literal_search(&sema, &syntax, position)
+    {
+        (Some(name), ReferenceKind::StructLiteral)
+    } else {
+        (
+            sema.find_node_at_offset_with_descend::<ast::Name>(&syntax, position.offset),
+            ReferenceKind::Other,
+        )
+    };
 
     let RangeInfo { range, info: def } = find_name(&sema, &syntax, position, opt_name)?;
 
@@ -131,7 +135,8 @@ fn find_name(
         let range = name.syntax().text_range();
         return Some(RangeInfo::new(range, def));
     }
-    let name_ref = find_node_at_offset::<ast::NameRef>(&syntax, position.offset)?;
+    let name_ref =
+        sema.find_node_at_offset_with_descend::<ast::NameRef>(&syntax, position.offset)?;
     let def = classify_name_ref(sema, &name_ref)?.definition();
     let range = name_ref.syntax().text_range();
     Some(RangeInfo::new(range, def))
@@ -157,6 +162,7 @@ fn decl_access(def: &Definition, syntax: &SyntaxNode, range: TextRange) -> Optio
 }
 
 fn get_struct_def_name_for_struct_literal_search(
+    sema: &Semantics<RootDatabase>,
     syntax: &SyntaxNode,
     position: FilePosition,
 ) -> Option<ast::Name> {
@@ -164,10 +170,18 @@ fn get_struct_def_name_for_struct_literal_search(
         if right.kind() != SyntaxKind::L_CURLY && right.kind() != SyntaxKind::L_PAREN {
             return None;
         }
-        if let Some(name) = find_node_at_offset::<ast::Name>(&syntax, left.text_range().start()) {
+        if let Some(name) =
+            sema.find_node_at_offset_with_descend::<ast::Name>(&syntax, left.text_range().start())
+        {
             return name.syntax().ancestors().find_map(ast::StructDef::cast).and_then(|l| l.name());
         }
-        if find_node_at_offset::<ast::TypeParamList>(&syntax, left.text_range().start()).is_some() {
+        if sema
+            .find_node_at_offset_with_descend::<ast::TypeParamList>(
+                &syntax,
+                left.text_range().start(),
+            )
+            .is_some()
+        {
             return left.ancestors().find_map(ast::StructDef::cast).and_then(|l| l.name());
         }
     }
diff --git a/crates/ra_ide/src/references/rename.rs b/crates/ra_ide/src/references/rename.rs
index 7d1190af9..9acc6158a 100644
--- a/crates/ra_ide/src/references/rename.rs
+++ b/crates/ra_ide/src/references/rename.rs
@@ -250,6 +250,63 @@ mod tests {
     }
 
     #[test]
+    fn test_rename_for_macro_args_rev() {
+        test_rename(
+            r#"
+    macro_rules! foo {($i:ident) => {$i} }
+    fn main() {
+        let a = "test";
+        foo!(a<|>);
+    }"#,
+            "b",
+            r#"
+    macro_rules! foo {($i:ident) => {$i} }
+    fn main() {
+        let b = "test";
+        foo!(b);
+    }"#,
+        );
+    }
+
+    #[test]
+    fn test_rename_for_macro_define_fn() {
+        test_rename(
+            r#"
+    macro_rules! define_fn {($id:ident) => { fn $id{} }}
+    define_fn!(foo);
+    fn main() {
+        fo<|>o();
+    }"#,
+            "bar",
+            r#"
+    macro_rules! define_fn {($id:ident) => { fn $id{} }}
+    define_fn!(bar);
+    fn main() {
+        bar();
+    }"#,
+        );
+    }
+
+    #[test]
+    fn test_rename_for_macro_define_fn_rev() {
+        test_rename(
+            r#"
+    macro_rules! define_fn {($id:ident) => { fn $id{} }}
+    define_fn!(fo<|>o);
+    fn main() {
+        foo();
+    }"#,
+            "bar",
+            r#"
+    macro_rules! define_fn {($id:ident) => { fn $id{} }}
+    define_fn!(bar);
+    fn main() {
+        bar();
+    }"#,
+        );
+    }
+
+    #[test]
     fn test_rename_for_param_inside() {
         test_rename(
             r#"
diff --git a/crates/ra_ide_db/Cargo.toml b/crates/ra_ide_db/Cargo.toml
index de4f5bce0..c3921bd40 100644
--- a/crates/ra_ide_db/Cargo.toml
+++ b/crates/ra_ide_db/Cargo.toml
@@ -17,6 +17,7 @@ fst = { version = "0.4", default-features = false }
 rustc-hash = "1.1.0"
 superslice = "1.0.0"
 once_cell = "1.3.1"
+either = "1.5.3"
 
 ra_syntax = { path = "../ra_syntax" }
 ra_text_edit = { path = "../ra_text_edit" }
diff --git a/crates/ra_ide_db/src/imports_locator.rs b/crates/ra_ide_db/src/imports_locator.rs
index c96351982..bf0d8db60 100644
--- a/crates/ra_ide_db/src/imports_locator.rs
+++ b/crates/ra_ide_db/src/imports_locator.rs
@@ -1,7 +1,7 @@
 //! This module contains an import search funcionality that is provided to the ra_assists module.
 //! Later, this should be moved away to a separate crate that is accessible from the ra_assists module.
 
-use hir::{ModuleDef, Semantics};
+use hir::{MacroDef, ModuleDef, Semantics};
 use ra_prof::profile;
 use ra_syntax::{ast, AstNode, SyntaxKind::NAME};
 
@@ -10,6 +10,7 @@ use crate::{
     symbol_index::{self, FileSymbol, Query},
     RootDatabase,
 };
+use either::Either;
 
 pub struct ImportsLocator<'a> {
     sema: Semantics<'a, RootDatabase>,
@@ -20,7 +21,7 @@ impl<'a> ImportsLocator<'a> {
         Self { sema: Semantics::new(db) }
     }
 
-    pub fn find_imports(&mut self, name_to_import: &str) -> Vec<ModuleDef> {
+    pub fn find_imports(&mut self, name_to_import: &str) -> Vec<Either<ModuleDef, MacroDef>> {
         let _p = profile("search_for_imports");
         let db = self.sema.db;
 
@@ -43,7 +44,8 @@ impl<'a> ImportsLocator<'a> {
             .chain(lib_results.into_iter())
             .filter_map(|import_candidate| self.get_name_definition(&import_candidate))
             .filter_map(|name_definition_to_import| match name_definition_to_import {
-                Definition::ModuleDef(module_def) => Some(module_def),
+                Definition::ModuleDef(module_def) => Some(Either::Left(module_def)),
+                Definition::Macro(macro_def) => Some(Either::Right(macro_def)),
                 _ => None,
             })
             .collect()
diff --git a/crates/ra_ide_db/src/search.rs b/crates/ra_ide_db/src/search.rs
index cf78d3e41..117454695 100644
--- a/crates/ra_ide_db/src/search.rs
+++ b/crates/ra_ide_db/src/search.rs
@@ -10,9 +10,7 @@ use hir::{DefWithBody, HasSource, ModuleSource, Semantics};
 use once_cell::unsync::Lazy;
 use ra_db::{FileId, FileRange, SourceDatabaseExt};
 use ra_prof::profile;
-use ra_syntax::{
-    algo::find_node_at_offset, ast, match_ast, AstNode, TextRange, TextUnit, TokenAtOffset,
-};
+use ra_syntax::{ast, match_ast, AstNode, TextRange, TextUnit};
 use rustc_hash::FxHashMap;
 use test_utils::tested_by;
 
@@ -219,21 +217,11 @@ impl Definition {
                     continue;
                 }
 
-                let name_ref =
-                    if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(&tree, offset) {
+                let name_ref: ast::NameRef =
+                    if let Some(name_ref) = sema.find_node_at_offset_with_descend(&tree, offset) {
                         name_ref
                     } else {
-                        // Handle macro token cases
-                        let token = match tree.token_at_offset(offset) {
-                            TokenAtOffset::None => continue,
-                            TokenAtOffset::Single(t) => t,
-                            TokenAtOffset::Between(_, t) => t,
-                        };
-                        let expanded = sema.descend_into_macros(token);
-                        match ast::NameRef::cast(expanded.parent()) {
-                            Some(name_ref) => name_ref,
-                            _ => continue,
-                        }
+                        continue;
                     };
 
                 // FIXME: reuse sb
diff --git a/crates/ra_ide_db/src/symbol_index.rs b/crates/ra_ide_db/src/symbol_index.rs
index 884359ee3..0f46f93c1 100644
--- a/crates/ra_ide_db/src/symbol_index.rs
+++ b/crates/ra_ide_db/src/symbol_index.rs
@@ -362,6 +362,13 @@ fn to_symbol(node: &SyntaxNode) -> Option<(SmolStr, SyntaxNodePtr, TextRange)> {
             ast::TypeAliasDef(it) => { decl(it) },
             ast::ConstDef(it) => { decl(it) },
             ast::StaticDef(it) => { decl(it) },
+            ast::MacroCall(it) => {
+                if it.is_macro_rules().is_some() {
+                    decl(it)
+                } else {
+                    None
+                }
+            },
             _ => None,
         }
     }
diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index c2857dbfc..c7f9bd873 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -6,7 +6,7 @@ use std::{
 };
 
 use anyhow::{Context, Result};
-use cargo_metadata::{CargoOpt, Message, MetadataCommand, PackageId};
+use cargo_metadata::{BuildScript, CargoOpt, Message, MetadataCommand, PackageId};
 use ra_arena::{Arena, Idx};
 use ra_cargo_watch::run_cargo;
 use ra_db::Edition;
@@ -254,7 +254,7 @@ pub fn load_out_dirs(
         "check".to_string(),
         "--message-format=json".to_string(),
         "--manifest-path".to_string(),
-        format!("{}", cargo_toml.display()),
+        cargo_toml.display().to_string(),
     ];
 
     if cargo_features.all_features {
@@ -263,19 +263,15 @@ pub fn load_out_dirs(
         // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
         // https://github.com/oli-obk/cargo_metadata/issues/79
         args.push("--no-default-features".to_string());
-    } else if !cargo_features.features.is_empty() {
-        for feature in &cargo_features.features {
-            args.push(feature.clone());
-        }
+    } else {
+        args.extend(cargo_features.features.iter().cloned());
     }
 
-    let mut res = FxHashMap::default();
-    let mut child = run_cargo(&args, cargo_toml.parent(), &mut |message| {
+    let mut acc = FxHashMap::default();
+    let res = run_cargo(&args, cargo_toml.parent(), &mut |message| {
         match message {
-            Message::BuildScriptExecuted(message) => {
-                let package_id = message.package_id;
-                let out_dir = message.out_dir;
-                res.insert(package_id, out_dir);
+            Message::BuildScriptExecuted(BuildScript { package_id, out_dir, .. }) => {
+                acc.insert(package_id, out_dir);
             }
 
             Message::CompilerArtifact(_) => (),
@@ -285,6 +281,9 @@ pub fn load_out_dirs(
         true
     });
 
-    let _ = child.wait();
-    res
+    if let Err(err) = res {
+        log::error!("Failed to load outdirs: {:?}", err);
+    }
+
+    acc
 }
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index b500a74fb..a3ef9acdc 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -336,7 +336,7 @@ impl ProjectWorkspace {
                                 extern_source,
                             );
                             if cargo[tgt].kind == TargetKind::Lib {
-                                lib_tgt = Some(crate_id);
+                                lib_tgt = Some((crate_id, cargo[tgt].name.clone()));
                                 pkg_to_lib_crate.insert(pkg, crate_id);
                             }
                             if cargo[tgt].is_proc_macro {
@@ -363,7 +363,7 @@ impl ProjectWorkspace {
 
                     // Set deps to the core, std and to the lib target of the current package
                     for &from in pkg_crates.get(&pkg).into_iter().flatten() {
-                        if let Some(to) = lib_tgt {
+                        if let Some((to, name)) = lib_tgt.clone() {
                             if to != from
                                 && crate_graph
                                     .add_dep(
@@ -371,7 +371,7 @@ impl ProjectWorkspace {
                                         // For root projects with dashes in their name,
                                         // cargo metadata does not do any normalization,
                                         // so we do it ourselves currently
-                                        CrateName::normalize_dashes(&cargo[pkg].name),
+                                        CrateName::normalize_dashes(&name),
                                         to,
                                     )
                                     .is_err()
diff --git a/crates/ra_syntax/Cargo.toml b/crates/ra_syntax/Cargo.toml
index 8efc6b368..6fccc2303 100644
--- a/crates/ra_syntax/Cargo.toml
+++ b/crates/ra_syntax/Cargo.toml
@@ -11,7 +11,7 @@ repository = "https://github.com/rust-analyzer/rust-analyzer"
 doctest = false
 
 [dependencies]
-itertools = "0.8.2"
+itertools = "0.9.0"
 rowan = "0.9.1"
 rustc_lexer = "0.1.0"
 rustc-hash = "1.1.0"
diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index 344cf0fbe..4d463a3ef 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -1,6 +1,9 @@
 //! FIXME: write short doc here
 
-use std::ops::RangeInclusive;
+use std::{
+    fmt,
+    ops::{self, RangeInclusive},
+};
 
 use itertools::Itertools;
 use ra_text_edit::TextEditBuilder;
@@ -95,6 +98,10 @@ impl TreeDiff {
             builder.replace(from.text_range(), to.to_string())
         }
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.replacements.is_empty()
+    }
 }
 
 /// Finds minimal the diff, which, applied to `from`, will result in `to`.
@@ -218,44 +225,121 @@ fn _replace_children(
     with_children(parent, new_children)
 }
 
-/// Replaces descendants in the node, according to the mapping.
-///
-/// This is a type-unsafe low-level editing API, if you need to use it, prefer
-/// to create a type-safe abstraction on top of it instead.
-pub fn replace_descendants(
-    parent: &SyntaxNode,
-    map: impl Fn(&SyntaxElement) -> Option<SyntaxElement>,
-) -> SyntaxNode {
-    _replace_descendants(parent, &map)
+#[derive(Default)]
+pub struct SyntaxRewriter<'a> {
+    f: Option<Box<dyn Fn(&SyntaxElement) -> Option<SyntaxElement> + 'a>>,
+    //FIXME: add debug_assertions that all elements are in fact from the same file.
+    replacements: FxHashMap<SyntaxElement, Replacement>,
 }
 
-fn _replace_descendants(
-    parent: &SyntaxNode,
-    map: &dyn Fn(&SyntaxElement) -> Option<SyntaxElement>,
-) -> SyntaxNode {
-    //  FIXME: this could be made much faster.
-    let new_children = parent.children_with_tokens().map(|it| go(map, it)).collect::<Vec<_>>();
-    return with_children(parent, new_children);
+impl fmt::Debug for SyntaxRewriter<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("SyntaxRewriter").field("replacements", &self.replacements).finish()
+    }
+}
 
-    fn go(
-        map: &dyn Fn(&SyntaxElement) -> Option<SyntaxElement>,
-        element: SyntaxElement,
-    ) -> NodeOrToken<rowan::GreenNode, rowan::GreenToken> {
-        if let Some(replacement) = map(&element) {
+impl<'a> SyntaxRewriter<'a> {
+    pub fn from_fn(f: impl Fn(&SyntaxElement) -> Option<SyntaxElement> + 'a) -> SyntaxRewriter<'a> {
+        SyntaxRewriter { f: Some(Box::new(f)), replacements: FxHashMap::default() }
+    }
+    pub fn delete<T: Clone + Into<SyntaxElement>>(&mut self, what: &T) {
+        let what = what.clone().into();
+        let replacement = Replacement::Delete;
+        self.replacements.insert(what, replacement);
+    }
+    pub fn replace<T: Clone + Into<SyntaxElement>>(&mut self, what: &T, with: &T) {
+        let what = what.clone().into();
+        let replacement = Replacement::Single(with.clone().into());
+        self.replacements.insert(what, replacement);
+    }
+    pub fn replace_ast<T: AstNode>(&mut self, what: &T, with: &T) {
+        self.replace(what.syntax(), with.syntax())
+    }
+
+    pub fn rewrite(&self, node: &SyntaxNode) -> SyntaxNode {
+        if self.f.is_none() && self.replacements.is_empty() {
+            return node.clone();
+        }
+        self.rewrite_children(node)
+    }
+
+    pub fn rewrite_ast<N: AstNode>(self, node: &N) -> N {
+        N::cast(self.rewrite(node.syntax())).unwrap()
+    }
+
+    pub fn rewrite_root(&self) -> Option<SyntaxNode> {
+        assert!(self.f.is_none());
+        self.replacements
+            .keys()
+            .map(|element| match element {
+                SyntaxElement::Node(it) => it.clone(),
+                SyntaxElement::Token(it) => it.parent(),
+            })
+            .fold1(|a, b| least_common_ancestor(&a, &b).unwrap())
+    }
+
+    fn replacement(&self, element: &SyntaxElement) -> Option<Replacement> {
+        if let Some(f) = &self.f {
+            assert!(self.replacements.is_empty());
+            return f(element).map(Replacement::Single);
+        }
+        self.replacements.get(element).cloned()
+    }
+
+    fn rewrite_children(&self, node: &SyntaxNode) -> SyntaxNode {
+        //  FIXME: this could be made much faster.
+        let new_children =
+            node.children_with_tokens().flat_map(|it| self.rewrite_self(&it)).collect::<Vec<_>>();
+        with_children(node, new_children)
+    }
+
+    fn rewrite_self(
+        &self,
+        element: &SyntaxElement,
+    ) -> Option<NodeOrToken<rowan::GreenNode, rowan::GreenToken>> {
+        if let Some(replacement) = self.replacement(&element) {
             return match replacement {
-                NodeOrToken::Node(it) => NodeOrToken::Node(it.green().clone()),
-                NodeOrToken::Token(it) => NodeOrToken::Token(it.green().clone()),
+                Replacement::Single(NodeOrToken::Node(it)) => {
+                    Some(NodeOrToken::Node(it.green().clone()))
+                }
+                Replacement::Single(NodeOrToken::Token(it)) => {
+                    Some(NodeOrToken::Token(it.green().clone()))
+                }
+                Replacement::Delete => None,
             };
         }
-        match element {
+        let res = match element {
             NodeOrToken::Token(it) => NodeOrToken::Token(it.green().clone()),
-            NodeOrToken::Node(it) => {
-                NodeOrToken::Node(_replace_descendants(&it, map).green().clone())
-            }
-        }
+            NodeOrToken::Node(it) => NodeOrToken::Node(self.rewrite_children(it).green().clone()),
+        };
+        Some(res)
     }
 }
 
+impl<'a> ops::AddAssign for SyntaxRewriter<'_> {
+    fn add_assign(&mut self, rhs: SyntaxRewriter) {
+        assert!(rhs.f.is_none());
+        self.replacements.extend(rhs.replacements)
+    }
+}
+
+#[derive(Clone, Debug)]
+enum Replacement {
+    Delete,
+    Single(SyntaxElement),
+}
+
+/// Replaces descendants in the node, according to the mapping.
+///
+/// This is a type-unsafe low-level editing API, if you need to use it, prefer
+/// to create a type-safe abstraction on top of it instead.
+pub fn _replace_descendants(
+    parent: &SyntaxNode,
+    map: impl Fn(&SyntaxElement) -> Option<SyntaxElement>,
+) -> SyntaxNode {
+    SyntaxRewriter::from_fn(map).rewrite(parent)
+}
+
 fn with_children(
     parent: &SyntaxNode,
     new_children: Vec<NodeOrToken<rowan::GreenNode, rowan::GreenToken>>,
diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
index 68dae008f..f74c9f9c6 100644
--- a/crates/ra_syntax/src/ast/edit.rs
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -4,7 +4,6 @@
 use std::{iter, ops::RangeInclusive};
 
 use arrayvec::ArrayVec;
-use rustc_hash::FxHashMap;
 
 use crate::{
     algo,
@@ -17,6 +16,7 @@ use crate::{
     SyntaxKind::{ATTR, COMMENT, WHITESPACE},
     SyntaxNode, SyntaxToken, T,
 };
+use algo::{neighbor, SyntaxRewriter};
 
 impl ast::BinExpr {
     #[must_use]
@@ -255,6 +255,28 @@ impl ast::UseItem {
         }
         self.clone()
     }
+
+    pub fn remove(&self) -> SyntaxRewriter<'static> {
+        let mut res = SyntaxRewriter::default();
+        res.delete(self.syntax());
+        let next_ws = self
+            .syntax()
+            .next_sibling_or_token()
+            .and_then(|it| it.into_token())
+            .and_then(ast::Whitespace::cast);
+        if let Some(next_ws) = next_ws {
+            let ws_text = next_ws.syntax().text();
+            if ws_text.starts_with('\n') {
+                let rest = &ws_text[1..];
+                if rest.is_empty() {
+                    res.delete(next_ws.syntax())
+                } else {
+                    res.replace(next_ws.syntax(), &make::tokens::whitespace(rest));
+                }
+            }
+        }
+        res
+    }
 }
 
 impl ast::UseTree {
@@ -293,14 +315,30 @@ impl ast::UseTree {
             Some(res)
         }
     }
+
+    pub fn remove(&self) -> SyntaxRewriter<'static> {
+        let mut res = SyntaxRewriter::default();
+        res.delete(self.syntax());
+        for &dir in [Direction::Next, Direction::Prev].iter() {
+            if let Some(nb) = neighbor(self, dir) {
+                self.syntax()
+                    .siblings_with_tokens(dir)
+                    .skip(1)
+                    .take_while(|it| it.as_node() != Some(nb.syntax()))
+                    .for_each(|el| res.delete(&el));
+                return res;
+            }
+        }
+        res
+    }
 }
 
 #[must_use]
-pub fn strip_attrs_and_docs<N: ast::AttrsOwner>(node: &N) -> N {
-    N::cast(strip_attrs_and_docs_inner(node.syntax().clone())).unwrap()
+pub fn remove_attrs_and_docs<N: ast::AttrsOwner>(node: &N) -> N {
+    N::cast(remove_attrs_and_docs_inner(node.syntax().clone())).unwrap()
 }
 
-fn strip_attrs_and_docs_inner(mut node: SyntaxNode) -> SyntaxNode {
+fn remove_attrs_and_docs_inner(mut node: SyntaxNode) -> SyntaxNode {
     while let Some(start) =
         node.children_with_tokens().find(|it| it.kind() == ATTR || it.kind() == COMMENT)
     {
@@ -343,28 +381,24 @@ impl IndentLevel {
     }
 
     fn _increase_indent(self, node: SyntaxNode) -> SyntaxNode {
-        let replacements: FxHashMap<SyntaxElement, SyntaxElement> = node
-            .descendants_with_tokens()
+        let mut rewriter = SyntaxRewriter::default();
+        node.descendants_with_tokens()
             .filter_map(|el| el.into_token())
             .filter_map(ast::Whitespace::cast)
             .filter(|ws| {
                 let text = ws.syntax().text();
                 text.contains('\n')
             })
-            .map(|ws| {
-                (
-                    ws.syntax().clone().into(),
-                    make::tokens::whitespace(&format!(
-                        "{}{:width$}",
-                        ws.syntax().text(),
-                        "",
-                        width = self.0 as usize * 4
-                    ))
-                    .into(),
-                )
-            })
-            .collect();
-        algo::replace_descendants(&node, |n| replacements.get(n).cloned())
+            .for_each(|ws| {
+                let new_ws = make::tokens::whitespace(&format!(
+                    "{}{:width$}",
+                    ws.syntax().text(),
+                    "",
+                    width = self.0 as usize * 4
+                ));
+                rewriter.replace(ws.syntax(), &new_ws)
+            });
+        rewriter.rewrite(&node)
     }
 
     pub fn decrease_indent<N: AstNode>(self, node: N) -> N {
@@ -372,27 +406,21 @@ impl IndentLevel {
     }
 
     fn _decrease_indent(self, node: SyntaxNode) -> SyntaxNode {
-        let replacements: FxHashMap<SyntaxElement, SyntaxElement> = node
-            .descendants_with_tokens()
+        let mut rewriter = SyntaxRewriter::default();
+        node.descendants_with_tokens()
             .filter_map(|el| el.into_token())
             .filter_map(ast::Whitespace::cast)
             .filter(|ws| {
                 let text = ws.syntax().text();
                 text.contains('\n')
             })
-            .map(|ws| {
-                (
-                    ws.syntax().clone().into(),
-                    make::tokens::whitespace(
-                        &ws.syntax()
-                            .text()
-                            .replace(&format!("\n{:1$}", "", self.0 as usize * 4), "\n"),
-                    )
-                    .into(),
-                )
-            })
-            .collect();
-        algo::replace_descendants(&node, |n| replacements.get(n).cloned())
+            .for_each(|ws| {
+                let new_ws = make::tokens::whitespace(
+                    &ws.syntax().text().replace(&format!("\n{:1$}", "", self.0 as usize * 4), "\n"),
+                );
+                rewriter.replace(ws.syntax(), &new_ws)
+            });
+        rewriter.rewrite(&node)
     }
 }
 
@@ -442,12 +470,11 @@ pub trait AstNodeEdit: AstNode + Sized {
         &self,
         replacement_map: impl IntoIterator<Item = (D, D)>,
     ) -> Self {
-        let map = replacement_map
-            .into_iter()
-            .map(|(from, to)| (from.syntax().clone().into(), to.syntax().clone().into()))
-            .collect::<FxHashMap<SyntaxElement, _>>();
-        let new_syntax = algo::replace_descendants(self.syntax(), |n| map.get(n).cloned());
-        Self::cast(new_syntax).unwrap()
+        let mut rewriter = SyntaxRewriter::default();
+        for (from, to) in replacement_map {
+            rewriter.replace(from.syntax(), to.syntax())
+        }
+        rewriter.rewrite_ast(self)
     }
 }
 
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index c3ae8f90e..392731dac 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -4,7 +4,7 @@
 use itertools::Itertools;
 
 use crate::{
-    ast::{self, child_opt, children, AstNode, AttrInput, SyntaxNode},
+    ast::{self, child_opt, children, AstNode, AttrInput, NameOwner, SyntaxNode},
     SmolStr, SyntaxElement,
     SyntaxKind::*,
     SyntaxToken, T,
@@ -514,3 +514,14 @@ impl ast::Visibility {
         self.syntax().children_with_tokens().any(|it| it.kind() == T![super])
     }
 }
+
+impl ast::MacroCall {
+    pub fn is_macro_rules(&self) -> Option<ast::Name> {
+        let name_ref = self.path()?.segment()?.name_ref()?;
+        if name_ref.text() == "macro_rules" {
+            self.name()
+        } else {
+            None
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index 9f6f1cc53..1145b69e8 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -87,6 +87,9 @@ pub fn block_from_expr(e: ast::Expr) -> ast::Block {
 pub fn expr_unit() -> ast::Expr {
     expr_from_text("()")
 }
+pub fn expr_empty_block() -> ast::Expr {
+    expr_from_text("{}")
+}
 pub fn expr_unimplemented() -> ast::Expr {
     expr_from_text("unimplemented!()")
 }
@@ -136,6 +139,20 @@ pub fn placeholder_pat() -> ast::PlaceholderPat {
     }
 }
 
+/// Creates a tuple of patterns from an interator of patterns.
+///
+/// Invariant: `pats` must be length > 1
+///
+/// FIXME handle `pats` length == 1
+pub fn tuple_pat(pats: impl IntoIterator<Item = ast::Pat>) -> ast::TuplePat {
+    let pats_str = pats.into_iter().map(|p| p.to_string()).join(", ");
+    return from_text(&format!("({})", pats_str));
+
+    fn from_text(text: &str) -> ast::TuplePat {
+        ast_from_text(&format!("fn f({}: ())", text))
+    }
+}
+
 pub fn tuple_struct_pat(
     path: ast::Path,
     pats: impl IntoIterator<Item = ast::Pat>,
diff --git a/crates/rust-analyzer/Cargo.toml b/crates/rust-analyzer/Cargo.toml
index d44f0ef1d..e071e9b8d 100644
--- a/crates/rust-analyzer/Cargo.toml
+++ b/crates/rust-analyzer/Cargo.toml
@@ -17,7 +17,7 @@ anyhow = "1.0.26"
 crossbeam-channel = "0.4.0"
 env_logger = { version = "0.7.1", default-features = false }
 globset = "0.4.4"
-itertools = "0.8.2"
+itertools = "0.9.0"
 jod-thread = "0.1.0"
 log = "0.4.8"
 lsp-types = { version = "0.73.0", features = ["proposed"] }