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When encountering unexpected closure return type, point at return type/expression
``` error[E0271]: expected `{closure@fallback-closure-wrap.rs:18:40}` to be a closure that returns `()`, but it returns `!` --> $DIR/fallback-closure-wrap.rs:19:9 | LL | let error = Closure::wrap(Box::new(move || { | ------- LL | panic!("Can't connect to server."); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `!` | = note: expected unit type `()` found type `!` = note: required for the cast from `Box<{closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47}>` to `Box<dyn FnMut()>` ``` ``` error[E0271]: expected `{closure@dont-ice-for-type-mismatch-in-closure-in-async.rs:6:10}` to be a closure that returns `bool`, but it returns `Option<()>` --> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:16 | LL | call(|| -> Option<()> { | ---- ------^^^^^^^^^^ | | | | | expected `bool`, found `Option<()>` | required by a bound introduced by this call | = note: expected type `bool` found enum `Option<()>` note: required by a bound in `call` --> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:3:25 | LL | fn call(_: impl Fn() -> bool) {} | ^^^^ required by this bound in `call` ``` ``` error[E0271]: expected `{closure@f670.rs:28:13}` to be a closure that returns `Result<(), _>`, but it returns `!` --> f670.rs:28:20 | 28 | let c = |e| -> ! { | -------^ | | | expected `Result<(), _>`, found `!` ... 32 | f().or_else(c); | ------- required by a bound introduced by this call -Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs:1433:28 | = note: expected enum `Result<(), _>` found type `!` note: required by a bound in `Result::<T, E>::or_else` --> /home/gh-estebank/rust/library/core/src/result.rs:1406:39 | 1406 | pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> { | ^^^^^^^^^^^^ required by this bound in `Result::<T, E>::or_else` ```
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11 files changed

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lines changed

‎compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -618,6 +618,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
618618
);
619619
let hir = tcx.hir();
620620
infcx.err_ctxt().note_type_err(
621+
cause.span,
621622
&mut diag,
622623
&cause,
623624
hir.get_if_local(impl_m.def_id)
@@ -1047,6 +1048,7 @@ fn report_trait_method_mismatch<'tcx>(
10471048

10481049
cause.span = impl_err_span;
10491050
infcx.err_ctxt().note_type_err(
1051+
cause.span,
10501052
&mut diag,
10511053
&cause,
10521054
trait_err_span.map(|sp| (sp, Cow::from("type in trait"), false)),
@@ -1844,6 +1846,7 @@ fn compare_const_predicate_entailment<'tcx>(
18441846
});
18451847

18461848
infcx.err_ctxt().note_type_err(
1849+
cause.span,
18471850
&mut diag,
18481851
&cause,
18491852
trait_c_span.map(|span| (span, Cow::from("type in trait"), false)),

‎compiler/rustc_hir_analysis/src/check/mod.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -643,6 +643,7 @@ pub fn check_function_signature<'tcx>(
643643
let failure_code = cause.as_failure_code_diag(err, cause.span, vec![]);
644644
let mut diag = tcx.dcx().create_err(failure_code);
645645
err_ctxt.note_type_err(
646+
cause.span,
646647
&mut diag,
647648
&cause,
648649
None,

‎compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1113,6 +1113,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
11131113
let trace = mk_trace(provided_span, (formal_ty, expected_ty), provided_ty);
11141114
if let Some(e) = error {
11151115
self.err_ctxt().note_type_err(
1116+
trace.cause.span,
11161117
&mut err,
11171118
&trace.cause,
11181119
None,

‎compiler/rustc_passes/src/check_attr.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2334,6 +2334,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
23342334
}
23352335

23362336
infcx.err_ctxt().note_type_err(
2337+
cause.span,
23372338
&mut diag,
23382339
&cause,
23392340
None,

‎compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1142,15 +1142,14 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
11421142
#[instrument(level = "debug", skip(self, diag, secondary_span, prefer_label))]
11431143
pub fn note_type_err(
11441144
&self,
1145+
span: Span,
11451146
diag: &mut Diag<'_>,
11461147
cause: &ObligationCause<'tcx>,
11471148
secondary_span: Option<(Span, Cow<'static, str>, bool)>,
11481149
mut values: Option<ty::ParamEnvAnd<'tcx, ValuePairs<'tcx>>>,
11491150
terr: TypeError<'tcx>,
11501151
prefer_label: bool,
11511152
) {
1152-
let span = cause.span;
1153-
11541153
// For some types of errors, expected-found does not make
11551154
// sense, so just ignore the values we were given.
11561155
if let TypeError::CyclicTy(_) = terr {
@@ -1801,6 +1800,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
18011800
);
18021801
let mut diag = self.dcx().create_err(failure_code);
18031802
self.note_type_err(
1803+
span,
18041804
&mut diag,
18051805
&trace.cause,
18061806
None,

‎compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

Lines changed: 76 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -718,6 +718,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
718718
);
719719

720720
self.note_type_err(
721+
span,
721722
&mut diag,
722723
&obligation.cause,
723724
None,
@@ -910,12 +911,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
910911
}
911912
}
912913
let hir_id = self.tcx.local_def_id_to_hir_id(obligation.cause.body_id);
913-
let body_id = match self.tcx.hir_node(hir_id) {
914-
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. }) => body_id,
915-
_ => return false,
916-
};
917-
let ControlFlow::Break(expr) = (FindMethodSubexprOfTry { search_span: span })
918-
.visit_body(self.tcx.hir().body(*body_id))
914+
let Some(body_id) = self.tcx.hir_node(hir_id).body_id() else { return false };
915+
let ControlFlow::Break(expr) =
916+
(FindMethodSubexprOfTry { search_span: span }).visit_body(self.tcx.hir().body(body_id))
919917
else {
920918
return false;
921919
};
@@ -1366,22 +1364,50 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
13661364
_ => (None, error.err),
13671365
};
13681366

1369-
let msg = values
1367+
let (msg, span, closure_span) = values
13701368
.and_then(|(predicate, normalized_term, expected_term)| {
1371-
self.maybe_detailed_projection_msg(predicate, normalized_term, expected_term)
1369+
self.maybe_detailed_projection_msg(
1370+
obligation.cause.span,
1371+
predicate,
1372+
normalized_term,
1373+
expected_term,
1374+
)
13721375
})
13731376
.unwrap_or_else(|| {
13741377
let mut cx = FmtPrinter::new_with_limit(
13751378
self.tcx,
13761379
Namespace::TypeNS,
13771380
rustc_session::Limit(10),
13781381
);
1379-
with_forced_trimmed_paths!(format!("type mismatch resolving `{}`", {
1380-
self.resolve_vars_if_possible(predicate).print(&mut cx).unwrap();
1381-
cx.into_buffer()
1382-
}))
1382+
(
1383+
with_forced_trimmed_paths!(format!("type mismatch resolving `{}`", {
1384+
self.resolve_vars_if_possible(predicate).print(&mut cx).unwrap();
1385+
cx.into_buffer()
1386+
})),
1387+
obligation.cause.span,
1388+
None,
1389+
)
13831390
});
1384-
let mut diag = struct_span_code_err!(self.dcx(), obligation.cause.span, E0271, "{msg}");
1391+
let mut diag = struct_span_code_err!(self.dcx(), span, E0271, "{msg}");
1392+
if let Some(span) = closure_span {
1393+
// Mark the closure decl so that it is seen even if we are pointing at the return
1394+
// type or expression.
1395+
//
1396+
// error[E0271]: expected `{closure@foo.rs:41:16}` to be a closure that returns
1397+
// `Unit3`, but it returns `Unit4`
1398+
// --> $DIR/foo.rs:43:17
1399+
// |
1400+
// LL | let v = Unit2.m(
1401+
// | - required by a bound introduced by this call
1402+
// ...
1403+
// LL | f: |x| {
1404+
// | --- /* this span */
1405+
// LL | drop(x);
1406+
// LL | Unit4
1407+
// | ^^^^^ expected `Unit3`, found `Unit4`
1408+
// |
1409+
diag.span_label(span, "");
1410+
}
13851411

13861412
let secondary_span = (|| {
13871413
let ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)) =
@@ -1441,6 +1467,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
14411467
})();
14421468

14431469
self.note_type_err(
1470+
span,
14441471
&mut diag,
14451472
&obligation.cause,
14461473
secondary_span,
@@ -1461,34 +1488,63 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
14611488

14621489
fn maybe_detailed_projection_msg(
14631490
&self,
1491+
mut span: Span,
14641492
projection_term: ty::AliasTerm<'tcx>,
14651493
normalized_ty: ty::Term<'tcx>,
14661494
expected_ty: ty::Term<'tcx>,
1467-
) -> Option<String> {
1495+
) -> Option<(String, Span, Option<Span>)> {
14681496
let trait_def_id = projection_term.trait_def_id(self.tcx);
14691497
let self_ty = projection_term.self_ty();
14701498

14711499
with_forced_trimmed_paths! {
14721500
if self.tcx.is_lang_item(projection_term.def_id, LangItem::FnOnceOutput) {
14731501
let fn_kind = self_ty.prefix_string(self.tcx);
1502+
let (span, closure_span) = if let ty::Closure(def_id, _) = self_ty.kind() {
1503+
let def_span = self.tcx.def_span(def_id);
1504+
let node = self.tcx.hir_node_by_def_id(def_id.as_local().unwrap());
1505+
if let Some(fn_decl) = node.fn_decl() {
1506+
span = match fn_decl.output {
1507+
hir::FnRetTy::Return(ty) => ty.span,
1508+
hir::FnRetTy::DefaultReturn(_) => {
1509+
let body = self.tcx.hir().body(node.body_id().unwrap());
1510+
match body.value.kind {
1511+
hir::ExprKind::Block(
1512+
hir::Block { expr: Some(expr), .. },
1513+
_,
1514+
) => expr.span,
1515+
hir::ExprKind::Block(
1516+
hir::Block {
1517+
expr: None, stmts: [.., last], ..
1518+
},
1519+
_,
1520+
) => last.span,
1521+
_ => body.value.span,
1522+
}
1523+
}
1524+
};
1525+
}
1526+
(span, Some(def_span))
1527+
} else {
1528+
(span, None)
1529+
};
14741530
let item = match self_ty.kind() {
14751531
ty::FnDef(def, _) => self.tcx.item_name(*def).to_string(),
14761532
_ => self_ty.to_string(),
14771533
};
1478-
Some(format!(
1534+
Some((format!(
14791535
"expected `{item}` to be a {fn_kind} that returns `{expected_ty}`, but it \
14801536
returns `{normalized_ty}`",
1481-
))
1537+
), span, closure_span))
14821538
} else if self.tcx.is_lang_item(trait_def_id, LangItem::Future) {
1483-
Some(format!(
1539+
Some((format!(
14841540
"expected `{self_ty}` to be a future that resolves to `{expected_ty}`, but it \
14851541
resolves to `{normalized_ty}`"
1486-
))
1542+
), span, None))
14871543
} else if Some(trait_def_id) == self.tcx.get_diagnostic_item(sym::Iterator) {
1488-
Some(format!(
1544+
Some((format!(
14891545
"expected `{self_ty}` to be an iterator that yields `{expected_ty}`, but it \
14901546
yields `{normalized_ty}`"
1491-
))
1547+
), span, None))
14921548
} else {
14931549
None
14941550
}

‎tests/ui/async-await/dont-ice-for-type-mismatch-in-closure-in-async.stderr

Lines changed: 6 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -21,19 +21,13 @@ LL | true
2121
found type `bool`
2222

2323
error[E0271]: expected `{closure@dont-ice-for-type-mismatch-in-closure-in-async.rs:6:10}` to be a closure that returns `bool`, but it returns `Option<()>`
24-
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:10
24+
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:16
2525
|
26-
LL | call(|| -> Option<()> {
27-
| _____----_^
28-
| | |
29-
| | required by a bound introduced by this call
30-
LL | |
31-
LL | | if true {
32-
LL | | false
33-
... |
34-
LL | |
35-
LL | | })
36-
| |_____^ expected `bool`, found `Option<()>`
26+
LL | call(|| -> Option<()> {
27+
| ---- ------^^^^^^^^^^
28+
| | |
29+
| | expected `bool`, found `Option<()>`
30+
| required by a bound introduced by this call
3731
|
3832
= note: expected type `bool`
3933
found enum `Option<()>`

‎tests/ui/higher-ranked/trait-bounds/issue-62203-hrtb-ice.rs

Lines changed: 2 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -36,12 +36,10 @@ trait Ty<'a> {
3636

3737
fn main() {
3838
let v = Unit2.m(
39-
L {
40-
//~^ ERROR to be a closure that returns `Unit3`, but it returns `Unit4`
41-
//~| ERROR type mismatch
39+
L { //~ ERROR type mismatch
4240
f: |x| {
4341
drop(x);
44-
Unit4
42+
Unit4 //~ ERROR to be a closure that returns `Unit3`, but it returns `Unit4`
4543
},
4644
},
4745
);

‎tests/ui/higher-ranked/trait-bounds/issue-62203-hrtb-ice.stderr

Lines changed: 17 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -1,16 +1,15 @@
1-
error[E0271]: type mismatch resolving `<L<{closure@issue-62203-hrtb-ice.rs:42:16}> as T0<'r, (&u8,)>>::O == <_ as Ty<'r>>::V`
1+
error[E0271]: type mismatch resolving `<L<{closure@issue-62203-hrtb-ice.rs:40:16}> as T0<'r, (&u8,)>>::O == <_ as Ty<'r>>::V`
22
--> $DIR/issue-62203-hrtb-ice.rs:39:9
33
|
44
LL | let v = Unit2.m(
55
| - required by a bound introduced by this call
66
LL | / L {
7-
LL | |
8-
LL | |
97
LL | | f: |x| {
10-
... |
8+
LL | | drop(x);
9+
LL | | Unit4
1110
LL | | },
1211
LL | | },
13-
| |_________^ type mismatch resolving `<L<{closure@issue-62203-hrtb-ice.rs:42:16}> as T0<'r, (&u8,)>>::O == <_ as Ty<'r>>::V`
12+
| |_________^ type mismatch resolving `<L<{closure@issue-62203-hrtb-ice.rs:40:16}> as T0<'r, (&u8,)>>::O == <_ as Ty<'r>>::V`
1413
|
1514
note: expected this to be `<_ as Ty<'_>>::V`
1615
--> $DIR/issue-62203-hrtb-ice.rs:21:14
@@ -30,21 +29,19 @@ LL | where
3029
LL | F: for<'r> T0<'r, (<Self as Ty<'r>>::V,), O = <B as Ty<'r>>::V>,
3130
| ^^^^^^^^^^^^^^^^^^^^ required by this bound in `T1::m`
3231

33-
error[E0271]: expected `{closure@issue-62203-hrtb-ice.rs:42:16}` to be a closure that returns `Unit3`, but it returns `Unit4`
34-
--> $DIR/issue-62203-hrtb-ice.rs:39:9
35-
|
36-
LL | let v = Unit2.m(
37-
| - required by a bound introduced by this call
38-
LL | / L {
39-
LL | |
40-
LL | |
41-
LL | | f: |x| {
42-
... |
43-
LL | | },
44-
LL | | },
45-
| |_________^ expected `Unit3`, found `Unit4`
46-
|
47-
note: required for `L<{closure@$DIR/issue-62203-hrtb-ice.rs:42:16: 42:19}>` to implement `for<'r> T0<'r, (&'r u8,)>`
32+
error[E0271]: expected `{closure@issue-62203-hrtb-ice.rs:40:16}` to be a closure that returns `Unit3`, but it returns `Unit4`
33+
--> $DIR/issue-62203-hrtb-ice.rs:42:17
34+
|
35+
LL | let v = Unit2.m(
36+
| - required by a bound introduced by this call
37+
LL | L {
38+
LL | f: |x| {
39+
| ---
40+
LL | drop(x);
41+
LL | Unit4
42+
| ^^^^^ expected `Unit3`, found `Unit4`
43+
|
44+
note: required for `L<{closure@$DIR/issue-62203-hrtb-ice.rs:40:16: 40:19}>` to implement `for<'r> T0<'r, (&'r u8,)>`
4845
--> $DIR/issue-62203-hrtb-ice.rs:17:16
4946
|
5047
LL | impl<'a, A, T> T0<'a, A> for L<T>

‎tests/ui/never_type/fallback-closure-wrap.fallback.stderr

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1,16 +1,15 @@
11
error[E0271]: expected `{closure@fallback-closure-wrap.rs:18:40}` to be a closure that returns `()`, but it returns `!`
2-
--> $DIR/fallback-closure-wrap.rs:18:31
2+
--> $DIR/fallback-closure-wrap.rs:19:9
33
|
4-
LL | let error = Closure::wrap(Box::new(move || {
5-
| _______________________________^
6-
LL | |
7-
LL | | panic!("Can't connect to server.");
8-
LL | | }) as Box<dyn FnMut()>);
9-
| |______^ expected `()`, found `!`
4+
LL | let error = Closure::wrap(Box::new(move || {
5+
| -------
6+
LL | panic!("Can't connect to server.");
7+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `!`
108
|
119
= note: expected unit type `()`
1210
found type `!`
1311
= note: required for the cast from `Box<{closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47}>` to `Box<dyn FnMut()>`
12+
= note: this error originates in the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
1413

1514
error: aborting due to 1 previous error
1615

‎tests/ui/never_type/fallback-closure-wrap.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,8 +16,8 @@ use std::marker::PhantomData;
1616

1717
fn main() {
1818
let error = Closure::wrap(Box::new(move || {
19-
//[fallback]~^ to be a closure that returns `()`, but it returns `!`
2019
panic!("Can't connect to server.");
20+
//[fallback]~^ to be a closure that returns `()`, but it returns `!`
2121
}) as Box<dyn FnMut()>);
2222
}
2323

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