14 files changed, 331 insertions, 300 deletions

diff --git a/crates/ide_assists/src/handlers/add_explicit_type.rs b/crates/ide_assists/src/handlers/add_explicit_type.rs
index cb1548cef..62db31952 100644
--- a/crates/ide_assists/src/handlers/add_explicit_type.rs
+++ b/crates/ide_assists/src/handlers/add_explicit_type.rs
@@ -34,26 +34,33 @@ pub(crate) fn add_explicit_type(acc: &mut Assists, ctx: &AssistContext) -> Optio
     // The binding must have a name
     let name = pat.name()?;
     let name_range = name.syntax().text_range();
-    let stmt_range = let_stmt.syntax().text_range();
-    let eq_range = let_stmt.eq_token()?.text_range();
+
     // Assist should only be applicable if cursor is between 'let' and '='
-    let let_range = TextRange::new(stmt_range.start(), eq_range.start());
-    let cursor_in_range = let_range.contains_range(ctx.frange.range);
+    let cursor_in_range = {
+        let stmt_range = let_stmt.syntax().text_range();
+        let eq_range = let_stmt.eq_token()?.text_range();
+        let let_range = TextRange::new(stmt_range.start(), eq_range.start());
+        let_range.contains_range(ctx.frange.range)
+    };
     if !cursor_in_range {
+        cov_mark::hit!(add_explicit_type_not_applicable_if_cursor_after_equals);
         return None;
     }
+
     // Assist not applicable if the type has already been specified
     // and it has no placeholders
     let ascribed_ty = let_stmt.ty();
     if let Some(ty) = &ascribed_ty {
         if ty.syntax().descendants().find_map(ast::InferType::cast).is_none() {
+            cov_mark::hit!(add_explicit_type_not_applicable_if_ty_already_specified);
             return None;
         }
     }
+
     // Infer type
     let ty = ctx.sema.type_of_expr(&expr)?;
-
     if ty.contains_unknown() || ty.is_closure() {
+        cov_mark::hit!(add_explicit_type_not_applicable_if_ty_not_inferred);
         return None;
     }
 
@@ -81,17 +88,25 @@ mod tests {
 
     #[test]
     fn add_explicit_type_target() {
-        check_assist_target(add_explicit_type, "fn f() { let a$0 = 1; }", "a");
+        check_assist_target(add_explicit_type, r#"fn f() { let a$0 = 1; }"#, "a");
     }
 
     #[test]
     fn add_explicit_type_works_for_simple_expr() {
-        check_assist(add_explicit_type, "fn f() { let a$0 = 1; }", "fn f() { let a: i32 = 1; }");
+        check_assist(
+            add_explicit_type,
+            r#"fn f() { let a$0 = 1; }"#,
+            r#"fn f() { let a: i32 = 1; }"#,
+        );
     }
 
     #[test]
     fn add_explicit_type_works_for_underscore() {
-        check_assist(add_explicit_type, "fn f() { let a$0: _ = 1; }", "fn f() { let a: i32 = 1; }");
+        check_assist(
+            add_explicit_type,
+            r#"fn f() { let a$0: _ = 1; }"#,
+            r#"fn f() { let a: i32 = 1; }"#,
+        );
     }
 
     #[test]
@@ -99,23 +114,19 @@ mod tests {
         check_assist(
             add_explicit_type,
             r#"
-            enum Option<T> {
-                Some(T),
-                None
-            }
+enum Option<T> { Some(T), None }
 
-            fn f() {
-                let a$0: Option<_> = Option::Some(1);
-            }"#,
+fn f() {
+    let a$0: Option<_> = Option::Some(1);
+}
+"#,
             r#"
-            enum Option<T> {
-                Some(T),
-                None
-            }
+enum Option<T> { Some(T), None }
 
-            fn f() {
-                let a: Option<i32> = Option::Some(1);
-            }"#,
+fn f() {
+    let a: Option<i32> = Option::Some(1);
+}
+"#,
         );
     }
 
@@ -139,24 +150,30 @@ mod tests {
 
     #[test]
     fn add_explicit_type_not_applicable_if_ty_not_inferred() {
-        check_assist_not_applicable(add_explicit_type, "fn f() { let a$0 = None; }");
+        cov_mark::check!(add_explicit_type_not_applicable_if_ty_not_inferred);
+        check_assist_not_applicable(add_explicit_type, r#"fn f() { let a$0 = None; }"#);
     }
 
     #[test]
     fn add_explicit_type_not_applicable_if_ty_already_specified() {
-        check_assist_not_applicable(add_explicit_type, "fn f() { let a$0: i32 = 1; }");
+        cov_mark::check!(add_explicit_type_not_applicable_if_ty_already_specified);
+        check_assist_not_applicable(add_explicit_type, r#"fn f() { let a$0: i32 = 1; }"#);
     }
 
     #[test]
     fn add_explicit_type_not_applicable_if_specified_ty_is_tuple() {
-        check_assist_not_applicable(add_explicit_type, "fn f() { let a$0: (i32, i32) = (3, 4); }");
+        check_assist_not_applicable(
+            add_explicit_type,
+            r#"fn f() { let a$0: (i32, i32) = (3, 4); }"#,
+        );
     }
 
     #[test]
     fn add_explicit_type_not_applicable_if_cursor_after_equals() {
+        cov_mark::check!(add_explicit_type_not_applicable_if_cursor_after_equals);
         check_assist_not_applicable(
             add_explicit_type,
-            "fn f() {let a =$0 match 1 {2 => 3, 3 => 5};}",
+            r#"fn f() {let a =$0 match 1 {2 => 3, 3 => 5};}"#,
         )
     }
 
@@ -164,7 +181,7 @@ mod tests {
     fn add_explicit_type_not_applicable_if_cursor_before_let() {
         check_assist_not_applicable(
             add_explicit_type,
-            "fn f() $0{let a = match 1 {2 => 3, 3 => 5};}",
+            r#"fn f() $0{let a = match 1 {2 => 3, 3 => 5};}"#,
         )
     }
 
@@ -176,7 +193,8 @@ mod tests {
 fn main() {
     let multiply_by_two$0 = |i| i * 3;
     let six = multiply_by_two(2);
-}"#,
+}
+"#,
         )
     }
 
@@ -185,23 +203,19 @@ fn main() {
         check_assist(
             add_explicit_type,
             r#"
-struct Test<K, T = u8> {
-    k: K,
-    t: T,
-}
+struct Test<K, T = u8> { k: K, t: T }
 
 fn main() {
     let test$0 = Test { t: 23u8, k: 33 };
-}"#,
-            r#"
-struct Test<K, T = u8> {
-    k: K,
-    t: T,
 }
+"#,
+            r#"
+struct Test<K, T = u8> { k: K, t: T }
 
 fn main() {
     let test: Test<i32> = Test { t: 23u8, k: 33 };
-}"#,
+}
+"#,
         );
     }
 }
diff --git a/crates/ide_assists/src/handlers/add_lifetime_to_type.rs b/crates/ide_assists/src/handlers/add_lifetime_to_type.rs
index 844928754..7030d0f97 100644
--- a/crates/ide_assists/src/handlers/add_lifetime_to_type.rs
+++ b/crates/ide_assists/src/handlers/add_lifetime_to_type.rs
@@ -1,5 +1,4 @@
-use ast::FieldList;
-use syntax::ast::{self, AstNode, GenericParamsOwner, NameOwner, RefType, Type};
+use syntax::ast::{self, AstNode, GenericParamsOwner, NameOwner};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -65,8 +64,8 @@ pub(crate) fn add_lifetime_to_type(acc: &mut Assists, ctx: &AssistContext) -> Op
     )
 }
 
-fn fetch_borrowed_types(node: &ast::Adt) -> Option<Vec<RefType>> {
-    let ref_types: Vec<RefType> = match node {
+fn fetch_borrowed_types(node: &ast::Adt) -> Option<Vec<ast::RefType>> {
+    let ref_types: Vec<ast::RefType> = match node {
         ast::Adt::Enum(enum_) => {
             let variant_list = enum_.variant_list()?;
             variant_list
@@ -88,7 +87,7 @@ fn fetch_borrowed_types(node: &ast::Adt) -> Option<Vec<RefType>> {
             record_field_list
                 .fields()
                 .filter_map(|r_field| {
-                    if let Type::RefType(ref_type) = r_field.ty()? {
+                    if let ast::Type::RefType(ref_type) = r_field.ty()? {
                         if ref_type.lifetime().is_none() {
                             return Some(ref_type);
                         }
@@ -107,12 +106,12 @@ fn fetch_borrowed_types(node: &ast::Adt) -> Option<Vec<RefType>> {
     }
 }
 
-fn find_ref_types_from_field_list(field_list: &FieldList) -> Option<Vec<RefType>> {
-    let ref_types: Vec<RefType> = match field_list {
+fn find_ref_types_from_field_list(field_list: &ast::FieldList) -> Option<Vec<ast::RefType>> {
+    let ref_types: Vec<ast::RefType> = match field_list {
         ast::FieldList::RecordFieldList(record_list) => record_list
             .fields()
             .filter_map(|f| {
-                if let Type::RefType(ref_type) = f.ty()? {
+                if let ast::Type::RefType(ref_type) = f.ty()? {
                     if ref_type.lifetime().is_none() {
                         return Some(ref_type);
                     }
@@ -124,7 +123,7 @@ fn find_ref_types_from_field_list(field_list: &FieldList) -> Option<Vec<RefType>
         ast::FieldList::TupleFieldList(tuple_field_list) => tuple_field_list
             .fields()
             .filter_map(|f| {
-                if let Type::RefType(ref_type) = f.ty()? {
+                if let ast::Type::RefType(ref_type) = f.ty()? {
                     if ref_type.lifetime().is_none() {
                         return Some(ref_type);
                     }
@@ -152,76 +151,79 @@ mod tests {
     fn add_lifetime_to_struct() {
         check_assist(
             add_lifetime_to_type,
-            "struct Foo { a: &$0i32 }",
-            "struct Foo<'a> { a: &'a i32 }",
+            r#"struct Foo { a: &$0i32 }"#,
+            r#"struct Foo<'a> { a: &'a i32 }"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "struct Foo { a: &$0i32, b: &usize }",
-            "struct Foo<'a> { a: &'a i32, b: &'a usize }",
+            r#"struct Foo { a: &$0i32, b: &usize }"#,
+            r#"struct Foo<'a> { a: &'a i32, b: &'a usize }"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "struct Foo { a: &$0i32, b: usize }",
-            "struct Foo<'a> { a: &'a i32, b: usize }",
+            r#"struct Foo { a: &$0i32, b: usize }"#,
+            r#"struct Foo<'a> { a: &'a i32, b: usize }"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "struct Foo<T> { a: &$0T, b: usize }",
-            "struct Foo<'a, T> { a: &'a T, b: usize }",
+            r#"struct Foo<T> { a: &$0T, b: usize }"#,
+            r#"struct Foo<'a, T> { a: &'a T, b: usize }"#,
         );
 
-        check_assist_not_applicable(add_lifetime_to_type, "struct Foo<'a> { a: &$0'a i32 }");
-        check_assist_not_applicable(add_lifetime_to_type, "struct Foo { a: &'a$0 i32 }");
+        check_assist_not_applicable(add_lifetime_to_type, r#"struct Foo<'a> { a: &$0'a i32 }"#);
+        check_assist_not_applicable(add_lifetime_to_type, r#"struct Foo { a: &'a$0 i32 }"#);
     }
 
     #[test]
     fn add_lifetime_to_enum() {
         check_assist(
             add_lifetime_to_type,
-            "enum Foo { Bar { a: i32 }, Other, Tuple(u32, &$0u32)}",
-            "enum Foo<'a> { Bar { a: i32 }, Other, Tuple(u32, &'a u32)}",
+            r#"enum Foo { Bar { a: i32 }, Other, Tuple(u32, &$0u32)}"#,
+            r#"enum Foo<'a> { Bar { a: i32 }, Other, Tuple(u32, &'a u32)}"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "enum Foo { Bar { a: &$0i32 }}",
-            "enum Foo<'a> { Bar { a: &'a i32 }}",
+            r#"enum Foo { Bar { a: &$0i32 }}"#,
+            r#"enum Foo<'a> { Bar { a: &'a i32 }}"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "enum Foo<T> { Bar { a: &$0i32, b: &T }}",
-            "enum Foo<'a, T> { Bar { a: &'a i32, b: &'a T }}",
+            r#"enum Foo<T> { Bar { a: &$0i32, b: &T }}"#,
+            r#"enum Foo<'a, T> { Bar { a: &'a i32, b: &'a T }}"#,
         );
 
-        check_assist_not_applicable(add_lifetime_to_type, "enum Foo<'a> { Bar { a: &$0'a i32 }}");
-        check_assist_not_applicable(add_lifetime_to_type, "enum Foo { Bar, $0Misc }");
+        check_assist_not_applicable(
+            add_lifetime_to_type,
+            r#"enum Foo<'a> { Bar { a: &$0'a i32 }}"#,
+        );
+        check_assist_not_applicable(add_lifetime_to_type, r#"enum Foo { Bar, $0Misc }"#);
     }
 
     #[test]
     fn add_lifetime_to_union() {
         check_assist(
             add_lifetime_to_type,
-            "union Foo { a: &$0i32 }",
-            "union Foo<'a> { a: &'a i32 }",
+            r#"union Foo { a: &$0i32 }"#,
+            r#"union Foo<'a> { a: &'a i32 }"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "union Foo { a: &$0i32, b: &usize }",
-            "union Foo<'a> { a: &'a i32, b: &'a usize }",
+            r#"union Foo { a: &$0i32, b: &usize }"#,
+            r#"union Foo<'a> { a: &'a i32, b: &'a usize }"#,
         );
 
         check_assist(
             add_lifetime_to_type,
-            "union Foo<T> { a: &$0T, b: usize }",
-            "union Foo<'a, T> { a: &'a T, b: usize }",
+            r#"union Foo<T> { a: &$0T, b: usize }"#,
+            r#"union Foo<'a, T> { a: &'a T, b: usize }"#,
         );
 
-        check_assist_not_applicable(add_lifetime_to_type, "struct Foo<'a> { a: &'a $0i32 }");
+        check_assist_not_applicable(add_lifetime_to_type, r#"struct Foo<'a> { a: &'a $0i32 }"#);
     }
 }
diff --git a/crates/ide_assists/src/handlers/add_missing_impl_members.rs b/crates/ide_assists/src/handlers/add_missing_impl_members.rs
index 63cea754d..0148635f9 100644
--- a/crates/ide_assists/src/handlers/add_missing_impl_members.rs
+++ b/crates/ide_assists/src/handlers/add_missing_impl_members.rs
@@ -3,9 +3,9 @@ use syntax::ast::{self, AstNode};
 
 use crate::{
     assist_context::{AssistContext, Assists},
-    utils::add_trait_assoc_items_to_impl,
-    utils::DefaultMethods,
-    utils::{filter_assoc_items, render_snippet, Cursor},
+    utils::{
+        add_trait_assoc_items_to_impl, filter_assoc_items, render_snippet, Cursor, DefaultMethods,
+    },
     AssistId, AssistKind,
 };
 
diff --git a/crates/ide_assists/src/handlers/convert_comment_block.rs b/crates/ide_assists/src/handlers/convert_comment_block.rs
index cdc45fc42..d202a85f9 100644
--- a/crates/ide_assists/src/handlers/convert_comment_block.rs
+++ b/crates/ide_assists/src/handlers/convert_comment_block.rs
@@ -1,14 +1,6 @@
 use itertools::Itertools;
-use std::convert::identity;
 use syntax::{
-    ast::{
-        self,
-        edit::IndentLevel,
-        Comment, CommentKind,
-        CommentPlacement::{Inner, Outer},
-        CommentShape::{self, Block, Line},
-        Whitespace,
-    },
+    ast::{self, edit::IndentLevel, Comment, CommentKind, CommentShape, Whitespace},
     AstToken, Direction, SyntaxElement, TextRange,
 };
 
@@ -30,21 +22,18 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 ///   */
 /// ```
 pub(crate) fn convert_comment_block(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
-    if let Some(comment) = ctx.find_token_at_offset::<ast::Comment>() {
-        // Only allow comments which are alone on their line
-        if let Some(prev) = comment.syntax().prev_token() {
-            if Whitespace::cast(prev).filter(|w| w.text().contains('\n')).is_none() {
-                return None;
-            }
+    let comment = ctx.find_token_at_offset::<ast::Comment>()?;
+    // Only allow comments which are alone on their line
+    if let Some(prev) = comment.syntax().prev_token() {
+        if Whitespace::cast(prev).filter(|w| w.text().contains('\n')).is_none() {
+            return None;
         }
-
-        return match comment.kind().shape {
-            ast::CommentShape::Block => block_to_line(acc, comment),
-            ast::CommentShape::Line => line_to_block(acc, comment),
-        };
     }
 
-    return None;
+    match comment.kind().shape {
+        ast::CommentShape::Block => block_to_line(acc, comment),
+        ast::CommentShape::Line => line_to_block(acc, comment),
+    }
 }
 
 fn block_to_line(acc: &mut Assists, comment: ast::Comment) -> Option<()> {
@@ -56,8 +45,7 @@ fn block_to_line(acc: &mut Assists, comment: ast::Comment) -> Option<()> {
         target,
         |edit| {
             let indentation = IndentLevel::from_token(comment.syntax());
-            let line_prefix =
-                comment_kind_prefix(CommentKind { shape: CommentShape::Line, ..comment.kind() });
+            let line_prefix = CommentKind { shape: CommentShape::Line, ..comment.kind() }.prefix();
 
             let text = comment.text();
             let text = &text[comment.prefix().len()..(text.len() - "*/".len())].trim();
@@ -106,7 +94,7 @@ fn line_to_block(acc: &mut Assists, comment: ast::Comment) -> Option<()> {
                 comments.into_iter().map(|c| line_comment_text(indentation, c)).join("\n");
 
             let block_prefix =
-                comment_kind_prefix(CommentKind { shape: CommentShape::Block, ..comment.kind() });
+                CommentKind { shape: CommentShape::Block, ..comment.kind() }.prefix();
 
             let output =
                 format!("{}\n{}\n{}*/", block_prefix, block_comment_body, indentation.to_string());
@@ -140,7 +128,7 @@ fn relevant_line_comments(comment: &ast::Comment) -> Vec<Comment> {
         .filter(|s| !skippable(s))
         .map(|not| not.into_token().and_then(Comment::cast).filter(same_prefix))
         .take_while(|opt_com| opt_com.is_some())
-        .filter_map(identity)
+        .flatten()
         .skip(1); // skip the first element so we don't duplicate it in next_comments
 
     let next_comments = comment
@@ -149,7 +137,7 @@ fn relevant_line_comments(comment: &ast::Comment) -> Vec<Comment> {
         .filter(|s| !skippable(s))
         .map(|not| not.into_token().and_then(Comment::cast).filter(same_prefix))
         .take_while(|opt_com| opt_com.is_some())
-        .filter_map(identity);
+        .flatten();
 
     let mut comments: Vec<_> = prev_comments.collect();
     comments.reverse();
@@ -183,17 +171,6 @@ fn line_comment_text(indentation: IndentLevel, comm: ast::Comment) -> String {
     }
 }
 
-fn comment_kind_prefix(ck: ast::CommentKind) -> &'static str {
-    match (ck.shape, ck.doc) {
-        (Line, Some(Inner)) => "//!",
-        (Line, Some(Outer)) => "///",
-        (Line, None) => "//",
-        (Block, Some(Inner)) => "/*!",
-        (Block, Some(Outer)) => "/**",
-        (Block, None) => "/*",
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use crate::tests::{check_assist, check_assist_not_applicable};
diff --git a/crates/ide_assists/src/handlers/early_return.rs b/crates/ide_assists/src/handlers/early_return.rs
index 9e0918477..c66f8c05d 100644
--- a/crates/ide_assists/src/handlers/early_return.rs
+++ b/crates/ide_assists/src/handlers/early_return.rs
@@ -56,7 +56,11 @@ pub(crate) fn convert_to_guarded_return(acc: &mut Assists, ctx: &AssistContext)
             match path.qualifier() {
                 None => {
                     let bound_ident = pat.fields().next().unwrap();
-                    Some((path, bound_ident))
+                    if ast::IdentPat::can_cast(bound_ident.syntax().kind()) {
+                        Some((path, bound_ident))
+                    } else {
+                        return None;
+                    }
                 }
                 Some(_) => return None,
             }
@@ -143,10 +147,7 @@ pub(crate) fn convert_to_guarded_return(acc: &mut Assists, ctx: &AssistContext)
                         make::expr_match(cond_expr, make::match_arm_list(vec![happy_arm, sad_arm]))
                     };
 
-                    let let_stmt = make::let_stmt(
-                        make::ident_pat(make::name(&bound_ident.syntax().to_string())).into(),
-                        Some(match_expr),
-                    );
+                    let let_stmt = make::let_stmt(bound_ident, Some(match_expr));
                     let let_stmt = let_stmt.indent(if_indent_level);
                     replace(let_stmt.syntax(), &then_block, &parent_block, &if_expr)
                 }
@@ -203,7 +204,7 @@ mod tests {
                 if$0 true {
                     foo();
 
-                    //comment
+                    // comment
                     bar();
                 }
             }
@@ -216,7 +217,7 @@ mod tests {
                 }
                 foo();
 
-                //comment
+                // comment
                 bar();
             }
             "#,
@@ -233,7 +234,7 @@ mod tests {
                 if$0 let Some(n) = n {
                     foo(n);
 
-                    //comment
+                    // comment
                     bar();
                 }
             }
@@ -247,7 +248,7 @@ mod tests {
                 };
                 foo(n);
 
-                //comment
+                // comment
                 bar();
             }
             "#,
@@ -284,10 +285,10 @@ mod tests {
             r#"
             fn main(n: Option<String>) {
                 bar();
-                if$0 let Ok(n) = n {
+                if$0 let Some(n) = n {
                     foo(n);
 
-                    //comment
+                    // comment
                     bar();
                 }
             }
@@ -296,12 +297,74 @@ mod tests {
             fn main(n: Option<String>) {
                 bar();
                 let n = match n {
-                    Ok(it) => it,
+                    Some(it) => it,
+                    _ => return,
+                };
+                foo(n);
+
+                // comment
+                bar();
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_let_mut_ok_inside_fn() {
+        check_assist(
+            convert_to_guarded_return,
+            r#"
+            fn main(n: Option<String>) {
+                bar();
+                if$0 let Some(mut n) = n {
+                    foo(n);
+
+                    // comment
+                    bar();
+                }
+            }
+            "#,
+            r#"
+            fn main(n: Option<String>) {
+                bar();
+                let mut n = match n {
+                    Some(it) => it,
+                    _ => return,
+                };
+                foo(n);
+
+                // comment
+                bar();
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_let_ref_ok_inside_fn() {
+        check_assist(
+            convert_to_guarded_return,
+            r#"
+            fn main(n: Option<&str>) {
+                bar();
+                if$0 let Some(ref n) = n {
+                    foo(n);
+
+                    // comment
+                    bar();
+                }
+            }
+            "#,
+            r#"
+            fn main(n: Option<&str>) {
+                bar();
+                let ref n = match n {
+                    Some(it) => it,
                     _ => return,
                 };
                 foo(n);
 
-                //comment
+                // comment
                 bar();
             }
             "#,
diff --git a/crates/ide_assists/src/handlers/expand_glob_import.rs b/crates/ide_assists/src/handlers/expand_glob_import.rs
index 83aa11d52..98389e4f7 100644
--- a/crates/ide_assists/src/handlers/expand_glob_import.rs
+++ b/crates/ide_assists/src/handlers/expand_glob_import.rs
@@ -136,18 +136,13 @@ impl Refs {
                 .into_iter()
                 .filter(|r| {
                     if let Def::ModuleDef(ModuleDef::Trait(tr)) = r.def {
-                        if tr
-                            .items(ctx.db())
-                            .into_iter()
-                            .find(|ai| {
-                                if let AssocItem::Function(f) = *ai {
-                                    Def::ModuleDef(ModuleDef::Function(f)).is_referenced_in(ctx)
-                                } else {
-                                    false
-                                }
-                            })
-                            .is_some()
-                        {
+                        if tr.items(ctx.db()).into_iter().any(|ai| {
+                            if let AssocItem::Function(f) = ai {
+                                Def::ModuleDef(ModuleDef::Function(f)).is_referenced_in(ctx)
+                            } else {
+                                false
+                            }
+                        }) {
                             return true;
                         }
                     }
diff --git a/crates/ide_assists/src/handlers/merge_imports.rs b/crates/ide_assists/src/handlers/merge_imports.rs
index 7bd7e1e36..8e0794218 100644
--- a/crates/ide_assists/src/handlers/merge_imports.rs
+++ b/crates/ide_assists/src/handlers/merge_imports.rs
@@ -1,8 +1,5 @@
 use ide_db::helpers::insert_use::{try_merge_imports, try_merge_trees, MergeBehavior};
-use syntax::{
-    algo::{neighbor, SyntaxRewriter},
-    ast, AstNode,
-};
+use syntax::{algo::neighbor, ast, ted, AstNode};
 
 use crate::{
     assist_context::{AssistContext, Assists},
@@ -24,33 +21,23 @@ use crate::{
 // ```
 pub(crate) fn merge_imports(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let tree: ast::UseTree = ctx.find_node_at_offset()?;
-    let mut rewriter = SyntaxRewriter::default();
-    let mut offset = ctx.offset();
 
+    let mut imports = None;
+    let mut uses = None;
     if let Some(use_item) = tree.syntax().parent().and_then(ast::Use::cast) {
-        let (merged, to_delete) =
+        let (merged, to_remove) =
             next_prev().filter_map(|dir| neighbor(&use_item, dir)).find_map(|use_item2| {
                 try_merge_imports(&use_item, &use_item2, MergeBehavior::Full).zip(Some(use_item2))
             })?;
 
-        rewriter.replace_ast(&use_item, &merged);
-        rewriter += to_delete.remove();
-
-        if to_delete.syntax().text_range().end() < offset {
-            offset -= to_delete.syntax().text_range().len();
-        }
+        imports = Some((use_item, merged, to_remove));
     } else {
-        let (merged, to_delete) =
+        let (merged, to_remove) =
             next_prev().filter_map(|dir| neighbor(&tree, dir)).find_map(|use_tree| {
                 try_merge_trees(&tree, &use_tree, MergeBehavior::Full).zip(Some(use_tree))
             })?;
 
-        rewriter.replace_ast(&tree, &merged);
-        rewriter += to_delete.remove();
-
-        if to_delete.syntax().text_range().end() < offset {
-            offset -= to_delete.syntax().text_range().len();
-        }
+        uses = Some((tree.clone(), merged, to_remove))
     };
 
     let target = tree.syntax().text_range();
@@ -59,7 +46,21 @@ pub(crate) fn merge_imports(acc: &mut Assists, ctx: &AssistContext) -> Option<()
         "Merge imports",
         target,
         |builder| {
-            builder.rewrite(rewriter);
+            if let Some((to_replace, replacement, to_remove)) = imports {
+                let to_replace = builder.make_ast_mut(to_replace);
+                let to_remove = builder.make_ast_mut(to_remove);
+
+                ted::replace(to_replace.syntax(), replacement.syntax());
+                to_remove.remove();
+            }
+
+            if let Some((to_replace, replacement, to_remove)) = uses {
+                let to_replace = builder.make_ast_mut(to_replace);
+                let to_remove = builder.make_ast_mut(to_remove);
+
+                ted::replace(to_replace.syntax(), replacement.syntax());
+                to_remove.remove()
+            }
         },
     )
 }
diff --git a/crates/ide_assists/src/handlers/move_bounds.rs b/crates/ide_assists/src/handlers/move_bounds.rs
index b5dec8014..011a28d44 100644
--- a/crates/ide_assists/src/handlers/move_bounds.rs
+++ b/crates/ide_assists/src/handlers/move_bounds.rs
@@ -21,7 +21,7 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // }
 // ```
 pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
-    let type_param_list = ctx.find_node_at_offset::<ast::GenericParamList>()?.clone_for_update();
+    let type_param_list = ctx.find_node_at_offset::<ast::GenericParamList>()?;
 
     let mut type_params = type_param_list.type_params();
     if type_params.all(|p| p.type_bound_list().is_none()) {
@@ -29,7 +29,6 @@ pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext
     }
 
     let parent = type_param_list.syntax().parent()?;
-    let original_parent_range = parent.text_range();
 
     let target = type_param_list.syntax().text_range();
     acc.add(
@@ -37,6 +36,9 @@ pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext
         "Move to where clause",
         target,
         |edit| {
+            let type_param_list = edit.make_ast_mut(type_param_list);
+            let parent = edit.make_mut(parent);
+
             let where_clause: ast::WhereClause = match_ast! {
                 match parent {
                     ast::Fn(it) => it.get_or_create_where_clause(),
@@ -56,8 +58,6 @@ pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext
                     tbl.remove()
                 }
             }
-
-            edit.replace(original_parent_range, parent.to_string())
         },
     )
 }
diff --git a/crates/ide_assists/src/handlers/qualify_path.rs b/crates/ide_assists/src/handlers/qualify_path.rs
index e7444f7db..f91770a76 100644
--- a/crates/ide_assists/src/handlers/qualify_path.rs
+++ b/crates/ide_assists/src/handlers/qualify_path.rs
@@ -536,6 +536,7 @@ fn main() {
     }
 
     #[test]
+    #[ignore = "FIXME: non-trait assoc items completion is unsupported yet, see FIXME in the import_assets.rs for more details"]
     fn associated_struct_const_unqualified() {
         check_assist(
             qualify_path,
diff --git a/crates/ide_assists/src/handlers/reorder_fields.rs b/crates/ide_assists/src/handlers/reorder_fields.rs
index 794c89323..383ca6c47 100644
--- a/crates/ide_assists/src/handlers/reorder_fields.rs
+++ b/crates/ide_assists/src/handlers/reorder_fields.rs
@@ -1,9 +1,6 @@
-use itertools::Itertools;
 use rustc_hash::FxHashMap;
 
-use hir::{Adt, ModuleDef, PathResolution, Semantics, Struct};
-use ide_db::RootDatabase;
-use syntax::{algo, ast, match_ast, AstNode, SyntaxKind, SyntaxKind::*, SyntaxNode};
+use syntax::{algo, ast, match_ast, AstNode, SyntaxKind::*, SyntaxNode};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -23,26 +20,39 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // ```
 //
 pub(crate) fn reorder_fields(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
-    reorder::<ast::RecordExpr>(acc, ctx).or_else(|| reorder::<ast::RecordPat>(acc, ctx))
-}
+    let record = ctx
+        .find_node_at_offset::<ast::RecordExpr>()
+        .map(|it| it.syntax().clone())
+        .or_else(|| ctx.find_node_at_offset::<ast::RecordPat>().map(|it| it.syntax().clone()))?;
 
-fn reorder<R: AstNode>(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
-    let record = ctx.find_node_at_offset::<R>()?;
-    let path = record.syntax().children().find_map(ast::Path::cast)?;
+    let path = record.children().find_map(ast::Path::cast)?;
 
     let ranks = compute_fields_ranks(&path, &ctx)?;
 
-    let fields = get_fields(&record.syntax());
-    let sorted_fields = sorted_by_rank(&fields, |node| {
-        *ranks.get(&get_field_name(node)).unwrap_or(&usize::max_value())
-    });
+    let fields: Vec<SyntaxNode> = {
+        let field_kind = match record.kind() {
+            RECORD_EXPR => RECORD_EXPR_FIELD,
+            RECORD_PAT => RECORD_PAT_FIELD,
+            _ => {
+                stdx::never!();
+                return None;
+            }
+        };
+        record.children().flat_map(|n| n.children()).filter(|n| n.kind() == field_kind).collect()
+    };
+
+    let sorted_fields = {
+        let mut fields = fields.clone();
+        fields.sort_by_key(|node| *ranks.get(&get_field_name(node)).unwrap_or(&usize::max_value()));
+        fields
+    };
 
     if sorted_fields == fields {
         cov_mark::hit!(reorder_sorted_fields);
         return None;
     }
 
-    let target = record.syntax().text_range();
+    let target = record.text_range();
     acc.add(
         AssistId("reorder_fields", AssistKind::RefactorRewrite),
         "Reorder record fields",
@@ -57,14 +67,6 @@ fn reorder<R: AstNode>(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     )
 }
 
-fn get_fields_kind(node: &SyntaxNode) -> Vec<SyntaxKind> {
-    match node.kind() {
-        RECORD_EXPR => vec![RECORD_EXPR_FIELD],
-        RECORD_PAT => vec![RECORD_PAT_FIELD, IDENT_PAT],
-        _ => vec![],
-    }
-}
-
 fn get_field_name(node: &SyntaxNode) -> String {
     let res = match_ast! {
         match node {
@@ -76,34 +78,20 @@ fn get_field_name(node: &SyntaxNode) -> String {
     res.unwrap_or_default()
 }
 
-fn get_fields(record: &SyntaxNode) -> Vec<SyntaxNode> {
-    let kinds = get_fields_kind(record);
-    record.children().flat_map(|n| n.children()).filter(|n| kinds.contains(&n.kind())).collect()
-}
-
-fn sorted_by_rank(
-    fields: &[SyntaxNode],
-    get_rank: impl Fn(&SyntaxNode) -> usize,
-) -> Vec<SyntaxNode> {
-    fields.iter().cloned().sorted_by_key(get_rank).collect()
-}
+fn compute_fields_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashMap<String, usize>> {
+    let strukt = match ctx.sema.resolve_path(path) {
+        Some(hir::PathResolution::Def(hir::ModuleDef::Adt(hir::Adt::Struct(it)))) => it,
+        _ => return None,
+    };
 
-fn struct_definition(path: &ast::Path, sema: &Semantics<RootDatabase>) -> Option<Struct> {
-    match sema.resolve_path(path) {
-        Some(PathResolution::Def(ModuleDef::Adt(Adt::Struct(s)))) => Some(s),
-        _ => None,
-    }
-}
+    let res = strukt
+        .fields(ctx.db())
+        .iter()
+        .enumerate()
+        .map(|(idx, field)| (field.name(ctx.db()).to_string(), idx))
+        .collect();
 
-fn compute_fields_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashMap<String, usize>> {
-    Some(
-        struct_definition(path, &ctx.sema)?
-            .fields(ctx.db())
-            .iter()
-            .enumerate()
-            .map(|(idx, field)| (field.name(ctx.db()).to_string(), idx))
-            .collect(),
-    )
+    Some(res)
 }
 
 #[cfg(test)]
@@ -118,11 +106,7 @@ mod tests {
         check_assist_not_applicable(
             reorder_fields,
             r#"
-struct Foo {
-    foo: i32,
-    bar: i32,
-}
-
+struct Foo { foo: i32, bar: i32 }
 const test: Foo = $0Foo { foo: 0, bar: 0 };
 "#,
         )
@@ -133,8 +117,8 @@ const test: Foo = $0Foo { foo: 0, bar: 0 };
         check_assist_not_applicable(
             reorder_fields,
             r#"
-struct Foo {};
-const test: Foo = $0Foo {}
+struct Foo {}
+const test: Foo = $0Foo {};
 "#,
         )
     }
@@ -144,12 +128,12 @@ const test: Foo = $0Foo {}
         check_assist(
             reorder_fields,
             r#"
-struct Foo {foo: i32, bar: i32};
-const test: Foo = $0Foo {bar: 0, foo: 1}
+struct Foo { foo: i32, bar: i32 }
+const test: Foo = $0Foo { bar: 0, foo: 1 };
 "#,
             r#"
-struct Foo {foo: i32, bar: i32};
-const test: Foo = Foo {foo: 1, bar: 0}
+struct Foo { foo: i32, bar: i32 }
+const test: Foo = Foo { foo: 1, bar: 0 };
 "#,
         )
     }
@@ -186,10 +170,7 @@ fn f(f: Foo) -> {
         check_assist(
             reorder_fields,
             r#"
-struct Foo {
-    foo: String,
-    bar: String,
-}
+struct Foo { foo: String, bar: String }
 
 impl Foo {
     fn new() -> Foo {
@@ -203,10 +184,7 @@ impl Foo {
 }
 "#,
             r#"
-struct Foo {
-    foo: String,
-    bar: String,
-}
+struct Foo { foo: String, bar: String }
 
 impl Foo {
     fn new() -> Foo {
diff --git a/crates/ide_assists/src/handlers/reorder_impl.rs b/crates/ide_assists/src/handlers/reorder_impl.rs
index edf4b0bfe..f976e73ad 100644
--- a/crates/ide_assists/src/handlers/reorder_impl.rs
+++ b/crates/ide_assists/src/handlers/reorder_impl.rs
@@ -95,7 +95,7 @@ fn compute_method_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashM
                 _ => None,
             })
             .enumerate()
-            .map(|(idx, func)| ((func.name(ctx.db()).to_string(), idx)))
+            .map(|(idx, func)| (func.name(ctx.db()).to_string(), idx))
             .collect(),
     )
 }
diff --git a/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs b/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs
index 88fe2fe90..4f0ef52ca 100644
--- a/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs
+++ b/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs
@@ -1,5 +1,5 @@
 use hir::ModuleDef;
-use ide_db::helpers::mod_path_to_ast;
+use ide_db::helpers::{import_assets::NameToImport, mod_path_to_ast};
 use ide_db::items_locator;
 use itertools::Itertools;
 use syntax::{
@@ -65,20 +65,24 @@ pub(crate) fn replace_derive_with_manual_impl(
     let current_module = ctx.sema.scope(annotated_name.syntax()).module()?;
     let current_crate = current_module.krate();
 
-    let found_traits =
-        items_locator::with_exact_name(&ctx.sema, current_crate, trait_token.text().to_string())
-            .into_iter()
-            .filter_map(|item| match ModuleDef::from(item.as_module_def_id()?) {
-                ModuleDef::Trait(trait_) => Some(trait_),
-                _ => None,
-            })
-            .flat_map(|trait_| {
-                current_module
-                    .find_use_path(ctx.sema.db, hir::ModuleDef::Trait(trait_))
-                    .as_ref()
-                    .map(mod_path_to_ast)
-                    .zip(Some(trait_))
-            });
+    let found_traits = items_locator::items_with_name(
+        &ctx.sema,
+        current_crate,
+        NameToImport::Exact(trait_token.text().to_string()),
+        items_locator::AssocItemSearch::Exclude,
+        Some(items_locator::DEFAULT_QUERY_SEARCH_LIMIT),
+    )
+    .filter_map(|item| match ModuleDef::from(item.as_module_def_id()?) {
+        ModuleDef::Trait(trait_) => Some(trait_),
+        _ => None,
+    })
+    .flat_map(|trait_| {
+        current_module
+            .find_use_path(ctx.sema.db, hir::ModuleDef::Trait(trait_))
+            .as_ref()
+            .map(mod_path_to_ast)
+            .zip(Some(trait_))
+    });
 
     let mut no_traits_found = true;
     for (trait_path, trait_) in found_traits.inspect(|_| no_traits_found = false) {
diff --git a/crates/ide_assists/src/handlers/unmerge_use.rs b/crates/ide_assists/src/handlers/unmerge_use.rs
index 616af7c2e..8d271e056 100644
--- a/crates/ide_assists/src/handlers/unmerge_use.rs
+++ b/crates/ide_assists/src/handlers/unmerge_use.rs
@@ -1,6 +1,6 @@
 use syntax::{
-    algo::SyntaxRewriter,
-    ast::{self, edit::AstNodeEdit, VisibilityOwner},
+    ast::{self, VisibilityOwner},
+    ted::{self, Position},
     AstNode, SyntaxKind,
 };
 
@@ -22,7 +22,7 @@ use crate::{
 // use std::fmt::Display;
 // ```
 pub(crate) fn unmerge_use(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
-    let tree: ast::UseTree = ctx.find_node_at_offset()?;
+    let tree: ast::UseTree = ctx.find_node_at_offset::<ast::UseTree>()?.clone_for_update();
 
     let tree_list = tree.syntax().parent().and_then(ast::UseTreeList::cast)?;
     if tree_list.use_trees().count() < 2 {
@@ -33,6 +33,9 @@ pub(crate) fn unmerge_use(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
     let use_: ast::Use = tree_list.syntax().ancestors().find_map(ast::Use::cast)?;
     let path = resolve_full_path(&tree)?;
 
+    let old_parent_range = use_.syntax().parent()?.text_range();
+    let new_parent = use_.syntax().parent()?;
+
     let target = tree.syntax().text_range();
     acc.add(
         AssistId("unmerge_use", AssistKind::RefactorRewrite),
@@ -47,20 +50,13 @@ pub(crate) fn unmerge_use(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
                     tree.rename(),
                     tree.star_token().is_some(),
                 ),
-            );
-
-            let mut rewriter = SyntaxRewriter::default();
-            rewriter += tree.remove();
-            rewriter.insert_after(use_.syntax(), &ast::make::tokens::single_newline());
-            if let ident_level @ 1..=usize::MAX = use_.indent_level().0 as usize {
-                rewriter.insert_after(
-                    use_.syntax(),
-                    &ast::make::tokens::whitespace(&" ".repeat(4 * ident_level)),
-                );
-            }
-            rewriter.insert_after(use_.syntax(), new_use.syntax());
-
-            builder.rewrite(rewriter);
+            )
+            .clone_for_update();
+
+            tree.remove();
+            ted::insert(Position::after(use_.syntax()), new_use.syntax());
+
+            builder.replace(old_parent_range, new_parent.to_string());
         },
     )
 }
diff --git a/crates/ide_assists/src/handlers/unwrap_block.rs b/crates/ide_assists/src/handlers/unwrap_block.rs
index 440639322..d3c3da018 100644
--- a/crates/ide_assists/src/handlers/unwrap_block.rs
+++ b/crates/ide_assists/src/handlers/unwrap_block.rs
@@ -186,7 +186,7 @@ fn main() {
     if true {$0
         foo();
 
-        //comment
+        // comment
         bar();
     } else {
         println!("bar");
@@ -198,7 +198,7 @@ fn main() {
     bar();
     foo();
 
-    //comment
+    // comment
     bar();
 }
 "#,
@@ -215,7 +215,7 @@ fn main() {
     if true {
         foo();
 
-        //comment
+        // comment
         bar();
     } else {$0
         println!("bar");
@@ -228,7 +228,7 @@ fn main() {
     if true {
         foo();
 
-        //comment
+        // comment
         bar();
     }
     println!("bar");
@@ -243,12 +243,12 @@ fn main() {
             unwrap_block,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {$0
         println!("bar");
     } else {
@@ -258,12 +258,12 @@ fn main() {
 "#,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     }
     println!("bar");
 }
@@ -277,12 +277,12 @@ fn main() {
             unwrap_block,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {
         println!("bar");
     } else if true {$0
@@ -292,12 +292,12 @@ fn main() {
 "#,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {
         println!("bar");
     }
@@ -313,12 +313,12 @@ fn main() {
             unwrap_block,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {
         println!("bar");
     } else if true {
@@ -330,12 +330,12 @@ fn main() {
 "#,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {
         println!("bar");
     } else if true {
@@ -353,12 +353,12 @@ fn main() {
             unwrap_block,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {
         println!("bar");
     } else if true {$0
@@ -370,12 +370,12 @@ fn main() {
 "#,
             r#"
 fn main() {
-    //bar();
+    // bar();
     if true {
         println!("true");
 
-        //comment
-        //bar();
+        // comment
+        // bar();
     } else if false {
         println!("bar");
     }
@@ -395,7 +395,7 @@ fn main() {
     if true {
         foo();
 
-        //comment
+        // comment
         bar();
     } else {
         println!("bar");
@@ -415,7 +415,7 @@ fn main() {
         if true {
             foo();
 
-            //comment
+            // comment
             bar();
         } else {
             println!("bar");
@@ -428,7 +428,7 @@ fn main() {
     if true {
         foo();
 
-        //comment
+        // comment
         bar();
     } else {
         println!("bar");
@@ -448,7 +448,7 @@ fn main() {
         if true {$0
             foo();
 
-            //comment
+            // comment
             bar();
         } else {
             println!("bar");
@@ -461,7 +461,7 @@ fn main() {
     for i in 0..5 {
         foo();
 
-        //comment
+        // comment
         bar();
     }
 }
@@ -479,7 +479,7 @@ fn main() {
         if true {
             foo();
 
-            //comment
+            // comment
             bar();
         } else {
             println!("bar");
@@ -492,7 +492,7 @@ fn main() {
     if true {
         foo();
 
-        //comment
+        // comment
         bar();
     } else {
         println!("bar");
@@ -512,7 +512,7 @@ fn main() {
         if true {
             foo();
 
-            //comment
+            // comment
             bar();
         } else {
             println!("bar");
@@ -525,7 +525,7 @@ fn main() {
     if true {
         foo();
 
-        //comment
+        // comment
         bar();
     } else {
         println!("bar");
@@ -569,7 +569,7 @@ fn main() {
         if true {
             foo();$0
 
-            //comment
+            // comment
             bar();
         } else {
             println!("bar");