1 files changed, 91 insertions, 9 deletions

diff --git a/crates/ra_assists/src/handlers/fill_match_arms.rs b/crates/ra_assists/src/handlers/fill_match_arms.rs
index add82e5b1..8d1af9933 100644
--- a/crates/ra_assists/src/handlers/fill_match_arms.rs
+++ b/crates/ra_assists/src/handlers/fill_match_arms.rs
@@ -1,15 +1,11 @@
-//! FIXME: write short doc here
-
 use std::iter;
 
 use hir::{Adt, HasSource, ModuleDef, Semantics};
 use itertools::Itertools;
 use ra_ide_db::RootDatabase;
+use ra_syntax::ast::{self, make, AstNode, MatchArm, NameOwner, Pat};
 
 use crate::{Assist, AssistCtx, AssistId};
-use ra_syntax::ast::{self, edit::IndentLevel, make, AstNode, NameOwner};
-
-use ast::{MatchArm, Pat};
 
 // Assist: fill_match_arms
 //
@@ -97,10 +93,7 @@ pub(crate) fn fill_match_arms(ctx: AssistCtx) -> Option<Assist> {
     }
 
     ctx.add_assist(AssistId("fill_match_arms"), "Fill match arms", |edit| {
-        arms.extend(missing_arms);
-
-        let indent_level = IndentLevel::from_node(match_arm_list.syntax());
-        let new_arm_list = indent_level.increase_indent(make::match_arm_list(arms));
+        let new_arm_list = match_arm_list.remove_placeholder().append_arms(missing_arms);
 
         edit.target(match_expr.syntax().text_range());
         edit.set_cursor(expr.syntax().text_range().start());
@@ -655,4 +648,93 @@ mod tests {
             "#,
         );
     }
+
+    #[test]
+    fn fill_match_arms_preserves_comments() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match a {
+                    // foo bar baz<|>
+                    A::One => {}
+                    // This is where the rest should be
+                }
+            }
+            "#,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match <|>a {
+                    // foo bar baz
+                    A::One => {}
+                    // This is where the rest should be
+                    A::Two => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_preserves_comments_empty() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match a {
+                    // foo bar baz<|>
+                }
+            }
+            "#,
+            r#"
+            enum A {
+                One,
+                Two,
+            }
+            fn foo(a: A) {
+                match <|>a {
+                    // foo bar baz
+                    A::One => {}
+                    A::Two => {}
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn fill_match_arms_placeholder() {
+        check_assist(
+            fill_match_arms,
+            r#"
+            enum A { One, Two, }
+            fn foo(a: A) {
+                match a<|> {
+                    _ => (),
+                }
+            }
+            "#,
+            r#"
+            enum A { One, Two, }
+            fn foo(a: A) {
+                match <|>a {
+                    A::One => {}
+                    A::Two => {}
+                }
+            }
+            "#,
+        );
+    }
 }