match_like_matches_macro: strip refs in suggestion

fixes rust-lang#6503

changelog: match_like_matches_macro: strip refs in suggestion (rust-lang#6503)

clippy_lints/src/matches.rs

@@ -1185,6 +1185,14 @@ fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr
  } else {
  pat
  };
+
+ // strip potential borrows (#6503), but only if the type is a reference
+ let mut ex_new = ex;
+ if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind {
+ if let ty::Ref(..) = cx.typeck_results().expr_ty(&ex_inner).kind() {
+ ex_new = ex_inner;
+ }
+ };
  span_lint_and_sugg(
  cx,
  MATCH_LIKE_MATCHES_MACRO,
@@ -1194,7 +1202,7 @@ fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr
  format!(
  "{}matches!({}, {})",
  if b0 { "" } else { "!" },
- snippet_with_applicability(cx, ex.span, "..", &mut applicability),
+ snippet_with_applicability(cx, ex_new.span, "..", &mut applicability),
  pat_and_guard,
  ),
  applicability,

tests/ui/match_expr_like_matches_macro.fixed

@@ -99,4 +99,44 @@ fn main() {
  _ => false,
  };
  }
+
+ {
+ // should print "z" in suggestion (#6503)
+ let z = &Some(3);
+ let _z = matches!(z, Some(3));
+ }
+
+ {
+ // this could also print "z" in suggestion..?
+ let z = Some(3);
+ let _z = matches!(&z, Some(3));
+ }
+
+ {
+ enum AnEnum {
+ X,
+ Y,
+ }
+
+ fn foo(_x: AnEnum) {}
+
+ fn main() {
+ let z = AnEnum::X;
+ // we can't remove the reference here!
+ let _ = matches!(&z, AnEnum::X);
+ foo(z);
+ }
+ }
+
+ {
+ struct S(i32);
+
+ fn fun(_val: Option<S>) {}
+
+ let val = Some(S(42));
+
+ let _res = matches!(&val, &Some(ref _a));
+
+ fun(val);
+ }
 }

tests/ui/match_expr_like_matches_macro.rs

@@ -119,4 +119,56 @@ fn main() {
  _ => false,
  };
  }
+
+ {
+ // should print "z" in suggestion (#6503)
+ let z = &Some(3);
+ let _z = match &z {
+ Some(3) => true,
+ _ => false,
+ };
+ }
+
+ {
+ // this could also print "z" in suggestion..?
+ let z = Some(3);
+ let _z = match &z {
+ Some(3) => true,
+ _ => false,
+ };
+ }
+
+ {
+ enum AnEnum {
+ X,
+ Y,
+ }
+
+ fn foo(_x: AnEnum) {}
+
+ fn main() {
+ let z = AnEnum::X;
+ // we can't remove the reference here!
+ let _ = match &z {
+ AnEnum::X => true,
+ _ => false,
+ };
+ foo(z);
+ }
+ }
+
+ {
+ struct S(i32);
+
+ fn fun(_val: Option<S>) {}
+
+ let val = Some(S(42));
+
+ let _res = match &val {
+ &Some(ref _a) => true,
+ _ => false,
+ };
+
+ fun(val);
+ }
 }

tests/ui/match_expr_like_matches_macro.stderr

@@ -70,5 +70,62 @@ LL | | _ => true,
 LL | | };
  | |_________^ help: try this: `!matches!(x, E::B(_) | E::C)`
 
-error: aborting due to 7 previous errors
+error: match expression looks like `matches!` macro
+ --> $DIR/match_expr_like_matches_macro.rs:126:18
+ |
+LL | let _z = match &z {
+ | __________________^
+LL | | Some(3) => true,
+LL | | _ => false,
+LL | | };
+ | |_________^ help: try this: `matches!(z, Some(3))`
+
+error: match expression looks like `matches!` macro
+ --> $DIR/match_expr_like_matches_macro.rs:135:18
+ |
+LL | let _z = match &z {
+ | __________________^
+LL | | Some(3) => true,
+LL | | _ => false,
+LL | | };
+ | |_________^ help: try this: `matches!(&z, Some(3))`
+
+error: match expression looks like `matches!` macro
+ --> $DIR/match_expr_like_matches_macro.rs:152:21
+ |
+LL | let _ = match &z {
+ | _____________________^
+LL | | AnEnum::X => true,
+LL | | _ => false,
+LL | | };
+ | |_____________^ help: try this: `matches!(&z, AnEnum::X)`
+
+error: match expression looks like `matches!` macro
+ --> $DIR/match_expr_like_matches_macro.rs:167:20
+ |
+LL | let _res = match &val {
+ | ____________________^
+LL | | &Some(ref _a) => true,
+LL | | _ => false,
+LL | | };
+ | |_________^ help: try this: `matches!(&val, &Some(ref _a))`
+
+error: you don't need to add `&` to both the expression and the patterns
+ --> $DIR/match_expr_like_matches_macro.rs:167:20
+ |
+LL | let _res = match &val {
+ | ____________________^
+LL | | &Some(ref _a) => true,
+LL | | _ => false,
+LL | | };
+ | |_________^
+ |
+ = note: `-D clippy::match-ref-pats` implied by `-D warnings`
+help: try
+ |
+LL | let _res = match val {
+LL | Some(ref _a) => true,
+ |
+
+error: aborting due to 12 previous errors