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Add more context to diagnostic
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+96
-18
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2 files changed

+96
-18
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‎src/librustc_infer/infer/error_reporting/nice_region_error/static_impl_trait.rs‎

Lines changed: 64 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -8,8 +8,10 @@ use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorRepor
88
use rustc_hir::def_id::{DefId, LOCAL_CRATE};
99
use rustc_hir::intravisit::{walk_ty, ErasedMap, NestedVisitorMap, Visitor};
1010
use rustc_hir::{self as hir, GenericBound, Item, ItemKind, Lifetime, LifetimeName, Node, TyKind};
11-
use rustc_middle::ty::{self, AssocItemContainer, RegionKind, Ty, TypeFoldable, TypeVisitor};
12-
use rustc_span::Span;
11+
use rustc_middle::ty::{
12+
self, AssocItem, AssocItemContainer, RegionKind, Ty, TypeFoldable, TypeVisitor,
13+
};
14+
use rustc_span::{MultiSpan, Span};
1315

1416
impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
1517
/// Print the error message for lifetime errors when the return type is a static impl Trait.
@@ -51,7 +53,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
5153
cause.span,
5254
"...is captured and required to live as long as `'static` here",
5355
);
54-
if self.find_impl_on_dyn_trait(&mut err, param.param_ty, &assoc.container) {
56+
if self.find_impl_on_dyn_trait(&mut err, param.param_ty, assoc) {
5557
err.emit();
5658
return Some(ErrorReported);
5759
} else {
@@ -131,7 +133,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
131133

132134
if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sup_origin {
133135
if let ObligationCauseCode::UnifyReceiver(assoc) = &cause.code {
134-
self.find_impl_on_dyn_trait(&mut err, param.param_ty, &assoc.container);
136+
self.find_impl_on_dyn_trait(&mut err, param.param_ty, assoc);
135137
}
136138
}
137139

@@ -263,7 +265,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
263265
&self,
264266
err: &mut DiagnosticBuilder<'_>,
265267
ty: Ty<'_>,
266-
container: &AssocItemContainer,
268+
assoc: &AssocItem,
267269
) -> bool {
268270
let tcx = self.tcx();
269271
let mut suggested = false;
@@ -272,7 +274,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
272274
let mut v = TraitObjectVisitor(vec![]);
273275
v.visit_ty(ty);
274276

275-
let container_id = match container {
277+
let container_id = match assoc.container {
276278
// When the obligation comes from an `impl Foo for dyn Bar {}`, we
277279
// have the `DefId` of the `trait` itself, not the relevant `impl`
278280
// block. Because of this, we have to look at all the `trait`s
@@ -284,16 +286,35 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
284286
// have the `DefId` of the relevant `Item`, so we use it directly.
285287
AssocItemContainer::ImplContainer(def_id) => {
286288
if let Some(Node::Item(Item { kind: ItemKind::Impl { self_ty, .. }, .. })) =
287-
tcx.hir().get_if_local(*def_id)
289+
tcx.hir().get_if_local(def_id)
288290
{
289291
for found_did in &v.0 {
290292
let mut hir_v = HirTraitObjectVisitor(vec![], *found_did);
291293
hir_v.visit_ty(self_ty);
292294
if let [span] = &hir_v.0[..] {
295+
let mut multi_span: MultiSpan = vec![*span].into();
296+
multi_span.push_span_label(
297+
*span,
298+
"this trait object has an implicit `'static` lifetime requirement"
299+
.to_string(),
300+
);
301+
multi_span.push_span_label(
302+
assoc.ident.span,
303+
"the `'static` requirement is introduced when calling this method"
304+
.to_string(),
305+
);
306+
err.span_note(
307+
multi_span,
308+
&format!(
309+
"when using method `{}` on `{}`, an implicit `'static` \
310+
requirement is introduced",
311+
assoc.ident,
312+
tcx.def_path_str(*found_did),
313+
),
314+
);
293315
err.span_suggestion_verbose(
294316
span.shrink_to_hi(),
295-
"this `impl` introduces an implicit `'static` requirement, \
296-
consider changing it",
317+
"consider relaxing the implicit `'static` requirement",
297318
" + '_".to_string(),
298319
Applicability::MaybeIncorrect,
299320
);
@@ -316,24 +337,53 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
316337
let impl_did = tcx.hir().local_def_id(*impl_node);
317338
match tcx.hir().get_if_local(impl_did.to_def_id()) {
318339
Some(Node::Item(Item {
319-
kind: ItemKind::Impl { self_ty, of_trait: Some(of_trait), .. },
340+
kind: ItemKind::Impl { self_ty, of_trait: Some(of_trait), items, .. },
320341
..
321-
})) if of_trait.trait_def_id() == Some(*container_id) => Some(self_ty),
342+
})) if of_trait.trait_def_id() == Some(container_id) => Some((
343+
self_ty,
344+
// Get the ident of the method, in order to use its `Span`.
345+
items
346+
.iter()
347+
.filter(|item| item.ident == assoc.ident)
348+
.map(|item| item.ident)
349+
.next()
350+
.unwrap_or(assoc.ident),
351+
)),
322352
_ => None,
323353
}
324354
});
325355

326356
// Given all the `impl`s of the relevant `trait`, look for those that are implemented for
327357
// the trait object in the `fn` parameter type.
328-
for self_ty in impl_self_tys {
358+
for (self_ty, method) in impl_self_tys {
329359
for found_did in &v.0 {
330360
let mut hir_v = HirTraitObjectVisitor(vec![], *found_did);
331361
hir_v.visit_ty(self_ty);
332362
if let [span] = &hir_v.0[..] {
363+
let mut multi_span: MultiSpan = vec![*span].into();
364+
multi_span.push_span_label(
365+
*span,
366+
"this trait object has an implicit `'static` lifetime requirement"
367+
.to_string(),
368+
);
369+
multi_span.push_span_label(
370+
method.span,
371+
"the `'static` requirement is introduced when calling this method"
372+
.to_string(),
373+
);
374+
err.span_note(
375+
multi_span,
376+
&format!(
377+
"when using method `{}` of trait `{}` on `{}`, an implicit `'static` \
378+
requirement is introduced",
379+
method,
380+
tcx.def_path_str(container_id),
381+
tcx.def_path_str(*found_did),
382+
),
383+
);
333384
err.span_suggestion_verbose(
334385
span.shrink_to_hi(),
335-
"this `impl` introduces an implicit `'static` requirement, \
336-
consider changing it",
386+
"consider relaxing the implicit `'static` requirement",
337387
" + '_".to_string(),
338388
Applicability::MaybeIncorrect,
339389
);

‎src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.stderr‎

Lines changed: 32 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,14 @@ LL | fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
66
LL | val.use_self()
77
| ^^^^^^^^ ...is captured and required to live as long as `'static` here
88
|
9-
help: this `impl` introduces an implicit `'static` requirement, consider changing it
9+
note: when using method `use_self` of trait `foo::MyTrait` on `foo::ObjectTrait`, an implicit `'static` requirement is introduced
10+
--> $DIR/impl-on-dyn-trait-with-implicit-static-bound.rs:14:26
11+
|
12+
LL | impl MyTrait for dyn ObjectTrait {
13+
| ^^^^^^^^^^^ this trait object has an implicit `'static` lifetime requirement
14+
LL | fn use_self(&self) -> &() { panic!() }
15+
| -------- the `'static` requirement is introduced when calling this method
16+
help: consider relaxing the implicit `'static` requirement
1017
|
1118
LL | impl MyTrait for dyn ObjectTrait + '_ {
1219
| ^^^^
@@ -19,7 +26,14 @@ LL | fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
1926
LL | val.use_self()
2027
| ^^^^^^^^ ...is captured and required to live as long as `'static` here
2128
|
22-
help: this `impl` introduces an implicit `'static` requirement, consider changing it
29+
note: when using method `use_self` on `bat::ObjectTrait`, an implicit `'static` requirement is introduced
30+
--> $DIR/impl-on-dyn-trait-with-implicit-static-bound.rs:64:14
31+
|
32+
LL | impl dyn ObjectTrait {
33+
| ^^^^^^^^^^^ this trait object has an implicit `'static` lifetime requirement
34+
LL | fn use_self(&self) -> &() { panic!() }
35+
| -------- the `'static` requirement is introduced when calling this method
36+
help: consider relaxing the implicit `'static` requirement
2337
|
2438
LL | impl dyn ObjectTrait + '_ {
2539
| ^^^^
@@ -32,7 +46,14 @@ LL | fn use_it<'a>(val: &'a dyn ObjectTrait) -> &'a () {
3246
LL | val.use_self()
3347
| ^^^^^^^^ ...is captured and required to live as long as `'static` here
3448
|
35-
help: this `impl` introduces an implicit `'static` requirement, consider changing it
49+
note: when using method `use_self` of trait `bar::MyTrait` on `bar::ObjectTrait`, an implicit `'static` requirement is introduced
50+
--> $DIR/impl-on-dyn-trait-with-implicit-static-bound.rs:31:26
51+
|
52+
LL | impl MyTrait for dyn ObjectTrait {
53+
| ^^^^^^^^^^^ this trait object has an implicit `'static` lifetime requirement
54+
LL | fn use_self(&self) -> &() { panic!() }
55+
| -------- the `'static` requirement is introduced when calling this method
56+
help: consider relaxing the implicit `'static` requirement
3657
|
3758
LL | impl MyTrait for dyn ObjectTrait + '_ {
3859
| ^^^^
@@ -45,7 +66,14 @@ LL | fn use_it<'a>(val: &'a Box<dyn ObjectTrait + 'a>) -> &'a () {
4566
LL | val.use_self()
4667
| ^^^^^^^^ ...is captured and required to live as long as `'static` here
4768
|
48-
help: this `impl` introduces an implicit `'static` requirement, consider changing it
69+
note: when using method `use_self` of trait `baz::MyTrait` on `baz::ObjectTrait`, an implicit `'static` requirement is introduced
70+
--> $DIR/impl-on-dyn-trait-with-implicit-static-bound.rs:48:30
71+
|
72+
LL | impl MyTrait for Box<dyn ObjectTrait> {
73+
| ^^^^^^^^^^^ this trait object has an implicit `'static` lifetime requirement
74+
LL | fn use_self(&self) -> &() { panic!() }
75+
| -------- the `'static` requirement is introduced when calling this method
76+
help: consider relaxing the implicit `'static` requirement
4977
|
5078
LL | impl MyTrait for Box<dyn ObjectTrait + '_> {
5179
| ^^^^

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