match_single_binding: Fix invalid suggestion when match scrutinee has…

… side effects

clippy_lints/src/matches.rs

@@ -1479,15 +1479,34 @@ fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[A
  );
  },
  PatKind::Wild => {
- span_lint_and_sugg(
- cx,
- MATCH_SINGLE_BINDING,
- expr.span,
- "this match could be replaced by its body itself",
- "consider using the match body instead",
- snippet_body,
- Applicability::MachineApplicable,
- );
+ if ex.can_have_side_effects() {
+ let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
+ let sugg = format!(
+ "{};\n{}{}",
+ snippet_with_applicability(cx, ex.span, "..", &mut applicability),
+ indent,
+ snippet_body
+ );
+ span_lint_and_sugg(
+ cx,
+ MATCH_SINGLE_BINDING,
+ expr.span,
+ "this match could be replaced by its scrutinee and body",
+ "consider using the scrutinee and body instead",
+ sugg,
+ applicability,
+ )
+ } else {
+ span_lint_and_sugg(
+ cx,
+ MATCH_SINGLE_BINDING,
+ expr.span,
+ "this match could be replaced by its body itself",
+ "consider using the match body instead",
+ snippet_body,
+ Applicability::MachineApplicable,
+ );
+ }
  },
  _ => (),
  }

tests/ui/match_single_binding.fixed

@@ -94,10 +94,7 @@ fn main() {
  0 => println!("Disabled branch"),
  _ => println!("Enabled branch"),
  }
- // Lint
- let x = 1;
- let y = 1;
- println!("Single branch");
+
  // Ok
  let x = 1;
  let y = 1;

tests/ui/match_single_binding.rs

@@ -106,15 +106,7 @@ fn main() {
  0 => println!("Disabled branch"),
  _ => println!("Enabled branch"),
  }
- // Lint
- let x = 1;
- let y = 1;
- match match y {
- 0 => 1,
- _ => 2,
- } {
- _ => println!("Single branch"),
- }
+
  // Ok
  let x = 1;
  let y = 1;

tests/ui/match_single_binding.stderr

@@ -167,16 +167,5 @@ LL | unwrapped
 LL | })
  |
 
-error: this match could be replaced by its body itself
- --> $DIR/match_single_binding.rs:112:5
- |
-LL | / match match y {
-LL | | 0 => 1,
-LL | | _ => 2,
-LL | | } {
-LL | | _ => println!("Single branch"),
-LL | | }
- | |_____^ help: consider using the match body instead: `println!("Single branch");`
-
-error: aborting due to 12 previous errors
+error: aborting due to 11 previous errors
 

tests/ui/match_single_binding2.fixed

@@ -34,4 +34,20 @@ fn main() {
  },
  None => println!("nothing"),
  }
+
+ fn side_effects() {}
+
+ // Lint (scrutinee has side effects)
+ // issue #7094
+ side_effects();
+ println!("Side effects");
+
+ // Lint (scrutinee has side effects)
+ // issue #7094
+ let x = 1;
+ match x {
+ 0 => 1,
+ _ => 2,
+ };
+ println!("Single branch");
 }

tests/ui/match_single_binding2.rs

@@ -34,4 +34,22 @@ fn main() {
  },
  None => println!("nothing"),
  }
+
+ fn side_effects() {}
+
+ // Lint (scrutinee has side effects)
+ // issue #7094
+ match side_effects() {
+ _ => println!("Side effects"),
+ }
+
+ // Lint (scrutinee has side effects)
+ // issue #7094
+ let x = 1;
+ match match x {
+ 0 => 1,
+ _ => 2,
+ } {
+ _ => println!("Single branch"),
+ }
 }

tests/ui/match_single_binding2.stderr

@@ -30,5 +30,39 @@ LL | let (a, b) = get_tup();
 LL | println!("a {:?} and b {:?}", a, b);
  |
 
-error: aborting due to 2 previous errors
+error: this match could be replaced by its scrutinee and body
+ --> $DIR/match_single_binding2.rs:42:5
+ |
+LL | / match side_effects() {
+LL | | _ => println!("Side effects"),
+LL | | }
+ | |_____^
+ |
+help: consider using the scrutinee and body instead
+ |
+LL | side_effects();
+LL | println!("Side effects");
+ |
+
+error: this match could be replaced by its scrutinee and body
+ --> $DIR/match_single_binding2.rs:49:5
+ |
+LL | / match match x {
+LL | | 0 => 1,
+LL | | _ => 2,
+LL | | } {
+LL | | _ => println!("Single branch"),
+LL | | }
+ | |_____^
+ |
+help: consider using the scrutinee and body instead
+ |
+LL | match x {
+LL | 0 => 1,
+LL | _ => 2,
+LL | };
+LL | println!("Single branch");
+ |
+
+error: aborting due to 4 previous errors