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EzrashawEzrashaw
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error-msg: expand suggestion for unused lint
1 parent e84e5ff commit 35103fe

9 files changed

+138
-31
lines changed

‎compiler/rustc_lint/src/lints.rs

+10-12
Original file line numberDiff line numberDiff line change
@@ -1390,7 +1390,7 @@ pub struct UnusedOp<'a> {
13901390
pub op: &'a str,
13911391
#[label]
13921392
pub label: Span,
1393-
#[suggestion(style = "verbose", code = "let _ = ", applicability = "machine-applicable")]
1393+
#[suggestion(style = "verbose", code = "let _ = ", applicability = "maybe-incorrect")]
13941394
pub suggestion: Span,
13951395
}
13961396

@@ -1434,17 +1434,15 @@ pub struct UnusedDef<'a, 'b> {
14341434
}
14351435

14361436
#[derive(Subdiagnostic)]
1437-
pub enum UnusedDefSuggestion {
1438-
#[suggestion(
1439-
lint_suggestion,
1440-
style = "verbose",
1441-
code = "let _ = ",
1442-
applicability = "machine-applicable"
1443-
)]
1444-
Default {
1445-
#[primary_span]
1446-
span: Span,
1447-
},
1437+
#[suggestion(
1438+
lint_suggestion,
1439+
style = "verbose",
1440+
code = "let _ = ",
1441+
applicability = "maybe-incorrect"
1442+
)]
1443+
pub struct UnusedDefSuggestion {
1444+
#[primary_span]
1445+
pub span: Span,
14481446
}
14491447

14501448
// Needed because of def_path_str

‎compiler/rustc_lint/src/unused.rs

+12-19
Original file line numberDiff line numberDiff line change
@@ -123,7 +123,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
123123
let must_use_result = is_ty_must_use(cx, ty, &expr, expr.span);
124124
let type_lint_emitted_or_suppressed = match must_use_result {
125125
Some(path) => {
126-
emit_must_use_untranslated(cx, &path, "", "", 1);
126+
emit_must_use_untranslated(cx, &path, "", "", 1, false);
127127
true
128128
}
129129
None => false,
@@ -358,6 +358,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
358358
descr_pre_path,
359359
descr_post_path,
360360
1,
361+
false,
361362
)
362363
})
363364
.is_some()
@@ -370,27 +371,30 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
370371
descr_pre: &str,
371372
descr_post: &str,
372373
plural_len: usize,
374+
is_inner: bool,
373375
) {
374376
let plural_suffix = pluralize!(plural_len);
375377

376378
match path {
377379
MustUsePath::Suppressed => {}
378380
MustUsePath::Boxed(path) => {
379381
let descr_pre = &format!("{}boxed ", descr_pre);
380-
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
382+
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len, true);
381383
}
382384
MustUsePath::Opaque(path) => {
383385
let descr_pre = &format!("{}implementer{} of ", descr_pre, plural_suffix);
384-
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
386+
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len, true);
385387
}
386388
MustUsePath::TraitObject(path) => {
387389
let descr_post = &format!(" trait object{}{}", plural_suffix, descr_post);
388-
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
390+
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len, true);
389391
}
390392
MustUsePath::TupleElement(elems) => {
391393
for (index, path) in elems {
392394
let descr_post = &format!(" in tuple element {}", index);
393-
emit_must_use_untranslated(cx, path, descr_pre, descr_post, plural_len);
395+
emit_must_use_untranslated(
396+
cx, path, descr_pre, descr_post, plural_len, true,
397+
);
394398
}
395399
}
396400
MustUsePath::Array(path, len) => {
@@ -401,6 +405,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
401405
descr_pre,
402406
descr_post,
403407
plural_len.saturating_add(usize::try_from(*len).unwrap_or(usize::MAX)),
408+
true,
404409
);
405410
}
406411
MustUsePath::Closure(span) => {
@@ -418,19 +423,6 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
418423
);
419424
}
420425
MustUsePath::Def(span, def_id, reason) => {
421-
let suggestion = if matches!(
422-
cx.tcx.get_diagnostic_name(*def_id),
423-
Some(sym::add)
424-
| Some(sym::sub)
425-
| Some(sym::mul)
426-
| Some(sym::div)
427-
| Some(sym::rem)
428-
| Some(sym::neg),
429-
) {
430-
Some(UnusedDefSuggestion::Default { span: span.shrink_to_lo() })
431-
} else {
432-
None
433-
};
434426
cx.emit_spanned_lint(
435427
UNUSED_MUST_USE,
436428
*span,
@@ -440,7 +432,8 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
440432
cx,
441433
def_id: *def_id,
442434
note: *reason,
443-
suggestion,
435+
suggestion: (!is_inner)
436+
.then_some(UnusedDefSuggestion { span: span.shrink_to_lo() }),
444437
},
445438
);
446439
}

‎tests/ui/conditional-compilation/cfg-attr-multi-true.stderr

+4
Original file line numberDiff line numberDiff line change
@@ -35,6 +35,10 @@ note: the lint level is defined here
3535
|
3636
LL | #![warn(unused_must_use)]
3737
| ^^^^^^^^^^^^^^^
38+
help: use `let _ = ...` to ignore the resulting value
39+
|
40+
LL | let _ = MustUseDeprecated::new();
41+
| +++++++
3842

3943
warning: 5 warnings emitted
4044

‎tests/ui/lint/fn_must_use.stderr

+28
Original file line numberDiff line numberDiff line change
@@ -10,12 +10,21 @@ note: the lint level is defined here
1010
|
1111
LL | #![warn(unused_must_use)]
1212
| ^^^^^^^^^^^^^^^
13+
help: use `let _ = ...` to ignore the resulting value
14+
|
15+
LL | let _ = need_to_use_this_value();
16+
| +++++++
1317

1418
warning: unused return value of `MyStruct::need_to_use_this_method_value` that must be used
1519
--> $DIR/fn_must_use.rs:60:5
1620
|
1721
LL | m.need_to_use_this_method_value();
1822
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
23+
|
24+
help: use `let _ = ...` to ignore the resulting value
25+
|
26+
LL | let _ = m.need_to_use_this_method_value();
27+
| +++++++
1928

2029
warning: unused return value of `EvenNature::is_even` that must be used
2130
--> $DIR/fn_must_use.rs:61:5
@@ -24,24 +33,43 @@ LL | m.is_even(); // trait method!
2433
| ^^^^^^^^^^^
2534
|
2635
= note: no side effects
36+
help: use `let _ = ...` to ignore the resulting value
37+
|
38+
LL | let _ = m.is_even(); // trait method!
39+
| +++++++
2740

2841
warning: unused return value of `MyStruct::need_to_use_this_associated_function_value` that must be used
2942
--> $DIR/fn_must_use.rs:64:5
3043
|
3144
LL | MyStruct::need_to_use_this_associated_function_value();
3245
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
46+
|
47+
help: use `let _ = ...` to ignore the resulting value
48+
|
49+
LL | let _ = MyStruct::need_to_use_this_associated_function_value();
50+
| +++++++
3351

3452
warning: unused return value of `std::cmp::PartialEq::eq` that must be used
3553
--> $DIR/fn_must_use.rs:70:5
3654
|
3755
LL | 2.eq(&3);
3856
| ^^^^^^^^
57+
|
58+
help: use `let _ = ...` to ignore the resulting value
59+
|
60+
LL | let _ = 2.eq(&3);
61+
| +++++++
3962

4063
warning: unused return value of `std::cmp::PartialEq::eq` that must be used
4164
--> $DIR/fn_must_use.rs:71:5
4265
|
4366
LL | m.eq(&n);
4467
| ^^^^^^^^
68+
|
69+
help: use `let _ = ...` to ignore the resulting value
70+
|
71+
LL | let _ = m.eq(&n);
72+
| +++++++
4573

4674
warning: unused comparison that must be used
4775
--> $DIR/fn_must_use.rs:74:5

‎tests/ui/lint/unused/must-use-box-from-raw.stderr

+4
Original file line numberDiff line numberDiff line change
@@ -10,6 +10,10 @@ note: the lint level is defined here
1010
|
1111
LL | #![warn(unused_must_use)]
1212
| ^^^^^^^^^^^^^^^
13+
help: use `let _ = ...` to ignore the resulting value
14+
|
15+
LL | let _ = Box::from_raw(ptr);
16+
| +++++++
1317

1418
warning: 1 warning emitted
1519

‎tests/ui/lint/unused/must_use-unit.stderr

+9
Original file line numberDiff line numberDiff line change
@@ -9,12 +9,21 @@ note: the lint level is defined here
99
|
1010
LL | #![deny(unused_must_use)]
1111
| ^^^^^^^^^^^^^^^
12+
help: use `let _ = ...` to ignore the resulting value
13+
|
14+
LL | let _ = foo();
15+
| +++++++
1216

1317
error: unused return value of `bar` that must be used
1418
--> $DIR/must_use-unit.rs:15:5
1519
|
1620
LL | bar();
1721
| ^^^^^
22+
|
23+
help: use `let _ = ...` to ignore the resulting value
24+
|
25+
LL | let _ = bar();
26+
| +++++++
1827

1928
error: aborting due to 2 previous errors
2029

‎tests/ui/lint/unused/unused-async.stderr

+20
Original file line numberDiff line numberDiff line change
@@ -16,12 +16,22 @@ error: unused return value of `foo` that must be used
1616
|
1717
LL | foo();
1818
| ^^^^^
19+
|
20+
help: use `let _ = ...` to ignore the resulting value
21+
|
22+
LL | let _ = foo();
23+
| +++++++
1924

2025
error: unused output of future returned by `foo` that must be used
2126
--> $DIR/unused-async.rs:33:5
2227
|
2328
LL | foo().await;
2429
| ^^^^^^^^^^^
30+
|
31+
help: use `let _ = ...` to ignore the resulting value
32+
|
33+
LL | let _ = foo().await;
34+
| +++++++
2535

2636
error: unused implementer of `Future` that must be used
2737
--> $DIR/unused-async.rs:34:5
@@ -36,12 +46,22 @@ error: unused return value of `bar` that must be used
3646
|
3747
LL | bar();
3848
| ^^^^^
49+
|
50+
help: use `let _ = ...` to ignore the resulting value
51+
|
52+
LL | let _ = bar();
53+
| +++++++
3954

4055
error: unused output of future returned by `bar` that must be used
4156
--> $DIR/unused-async.rs:36:5
4257
|
4358
LL | bar().await;
4459
| ^^^^^^^^^^^
60+
|
61+
help: use `let _ = ...` to ignore the resulting value
62+
|
63+
LL | let _ = bar().await;
64+
| +++++++
4565

4666
error: unused implementer of `Future` that must be used
4767
--> $DIR/unused-async.rs:37:5

‎tests/ui/lint/unused/unused-result.stderr

+17
Original file line numberDiff line numberDiff line change
@@ -9,6 +9,10 @@ note: the lint level is defined here
99
|
1010
LL | #![deny(unused_results, unused_must_use)]
1111
| ^^^^^^^^^^^^^^^
12+
help: use `let _ = ...` to ignore the resulting value
13+
|
14+
LL | let _ = foo::<MustUse>();
15+
| +++++++
1216

1317
error: unused `MustUseMsg` that must be used
1418
--> $DIR/unused-result.rs:22:5
@@ -17,6 +21,10 @@ LL | foo::<MustUseMsg>();
1721
| ^^^^^^^^^^^^^^^^^^^
1822
|
1923
= note: some message
24+
help: use `let _ = ...` to ignore the resulting value
25+
|
26+
LL | let _ = foo::<MustUseMsg>();
27+
| +++++++
2028

2129
error: unused result of type `isize`
2230
--> $DIR/unused-result.rs:34:5
@@ -35,6 +43,11 @@ error: unused `MustUse` that must be used
3543
|
3644
LL | foo::<MustUse>();
3745
| ^^^^^^^^^^^^^^^^
46+
|
47+
help: use `let _ = ...` to ignore the resulting value
48+
|
49+
LL | let _ = foo::<MustUse>();
50+
| +++++++
3851

3952
error: unused `MustUseMsg` that must be used
4053
--> $DIR/unused-result.rs:36:5
@@ -43,6 +56,10 @@ LL | foo::<MustUseMsg>();
4356
| ^^^^^^^^^^^^^^^^^^^
4457
|
4558
= note: some message
59+
help: use `let _ = ...` to ignore the resulting value
60+
|
61+
LL | let _ = foo::<MustUseMsg>();
62+
| +++++++
4663

4764
error: aborting due to 5 previous errors
4865

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