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Author: JohnTitor

compiler/rustc_lint/src/unused.rs

@@ -162,16 +162,13 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
  if let Some(must_use_op) = must_use_op {
  cx.struct_span_lint(UNUSED_MUST_USE, expr.span, |lint| {
  let mut lint = lint.build(&format!("unused {} that must be used", must_use_op));
- lint.note(&format!("the {} produces a value", must_use_op));
- if let Ok(snippet) = cx.sess().source_map().span_to_snippet(expr.span) {
- lint.span_suggestion(
- expr.span,
- "use `let _ = ...` to ignore it",
- format!("let _ = {}", snippet),
- Applicability::MachineApplicable,
- )
- .emit()
- }
+ lint.span_label(expr.span, &format!("the {} produces a value", must_use_op));
+ lint.span_suggestion_verbose(
+ expr.span.shrink_to_lo(),
+ "use `let _ = ...` to ignore the resulting value",
+ "let _ = ".to_string(),
+ Applicability::MachineApplicable,
+ );
  lint.emit();
  });
  op_warned = true;

src/test/ui/lint/fn_must_use.stderr

@@ -47,17 +47,23 @@ warning: unused comparison that must be used
  --> $DIR/fn_must_use.rs:74:5
  |
 LL | 2 == 3;
- | ^^^^^^ help: use `let _ = ...` to ignore it: `let _ = 2 == 3`
+ | ^^^^^^ the comparison produces a value
  |
- = note: the comparison produces a value
+help: use `let _ = ...` to ignore the resulting value
+ |
+LL | let _ = 2 == 3;
+ | ^^^^^^^
 
 warning: unused comparison that must be used
  --> $DIR/fn_must_use.rs:75:5
  |
 LL | m == n;
- | ^^^^^^ help: use `let _ = ...` to ignore it: `let _ = m == n`
+ | ^^^^^^ the comparison produces a value
+ |
+help: use `let _ = ...` to ignore the resulting value
  |
- = note: the comparison produces a value
+LL | let _ = m == n;
+ | ^^^^^^^
 
 warning: 8 warnings emitted
 

src/test/ui/lint/unused-borrows.stderr

@@ -2,54 +2,72 @@ error: unused borrow that must be used
  --> $DIR/unused-borrows.rs:6:5
  |
 LL | &42;
- | ^^^ help: use `let _ = ...` to ignore it: `let _ = &42`
+ | ^^^ the borrow produces a value
  |
 note: the lint level is defined here
  --> $DIR/unused-borrows.rs:1:9
  |
 LL | #![deny(unused_must_use)]
  | ^^^^^^^^^^^^^^^
- = note: the borrow produces a value
+help: use `let _ = ...` to ignore the resulting value
+ |
+LL | let _ = &42;
+ | ^^^^^^^
 
 error: unused borrow that must be used
  --> $DIR/unused-borrows.rs:9:5
  |
 LL | &mut foo(42);
- | ^^^^^^^^^^^^ help: use `let _ = ...` to ignore it: `let _ = &mut foo(42)`
+ | ^^^^^^^^^^^^ the borrow produces a value
+ |
+help: use `let _ = ...` to ignore the resulting value
  |
- = note: the borrow produces a value
+LL | let _ = &mut foo(42);
+ | ^^^^^^^
 
 error: unused borrow that must be used
  --> $DIR/unused-borrows.rs:12:5
  |
 LL | &&42;
- | ^^^^ help: use `let _ = ...` to ignore it: `let _ = &&42`
+ | ^^^^ the borrow produces a value
+ |
+help: use `let _ = ...` to ignore the resulting value
  |
- = note: the borrow produces a value
+LL | let _ = &&42;
+ | ^^^^^^^
 
 error: unused borrow that must be used
  --> $DIR/unused-borrows.rs:15:5
  |
 LL | &&mut 42;
- | ^^^^^^^^ help: use `let _ = ...` to ignore it: `let _ = &&mut 42`
+ | ^^^^^^^^ the borrow produces a value
  |
- = note: the borrow produces a value
+help: use `let _ = ...` to ignore the resulting value
+ |
+LL | let _ = &&mut 42;
+ | ^^^^^^^
 
 error: unused borrow that must be used
  --> $DIR/unused-borrows.rs:18:5
  |
 LL | &mut &42;
- | ^^^^^^^^ help: use `let _ = ...` to ignore it: `let _ = &mut &42`
+ | ^^^^^^^^ the borrow produces a value
+ |
+help: use `let _ = ...` to ignore the resulting value
  |
- = note: the borrow produces a value
+LL | let _ = &mut &42;
+ | ^^^^^^^
 
 error: unused borrow that must be used
  --> $DIR/unused-borrows.rs:23:5
  |
 LL | && foo(42);
- | ^^^^^^^^^^ help: use `let _ = ...` to ignore it: `let _ = && foo(42)`
+ | ^^^^^^^^^^ the borrow produces a value
+ |
+help: use `let _ = ...` to ignore the resulting value
  |
- = note: the borrow produces a value
+LL | let _ = && foo(42);
+ | ^^^^^^^
 
 error: aborting due to 6 previous errors
 

src/test/ui/lint/unused/issue-85913.stderr

@@ -2,14 +2,17 @@ error: unused logical operation that must be used
  --> $DIR/issue-85913.rs:4:5
  |
 LL | function() && return 1;
- | ^^^^^^^^^^^^^^^^^^^^^^ help: use `let _ = ...` to ignore it: `let _ = function() && return 1`
+ | ^^^^^^^^^^^^^^^^^^^^^^ the logical operation produces a value
  |
 note: the lint level is defined here
  --> $DIR/issue-85913.rs:1:9
  |
 LL | #![deny(unused_must_use)]
  | ^^^^^^^^^^^^^^^
- = note: the logical operation produces a value
+help: use `let _ = ...` to ignore the resulting value
+ |
+LL | let _ = function() && return 1;
+ | ^^^^^^^
 
 error: aborting due to previous error