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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