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rust-timerrust-timer
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Unrolled build for rust-lang#124690
Rollup merge of rust-lang#124690 - compiler-errors:only-ambig-if-ambig, r=lcnr Only consider ambiguous goals when finding best obligation for ambiguities We don't care about ambiguous goals when reporting true errors, and vice versa for ambiguities. r? lcnr
2 parents d568423 + 6714216 commit e73398a

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3 files changed

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‎compiler/rustc_trait_selection/src/solve/fulfill.rs

+11-9
Original file line numberDiff line numberDiff line change
@@ -137,7 +137,7 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
137137
.collect();
138138

139139
errors.extend(self.obligations.overflowed.drain(..).map(|obligation| FulfillmentError {
140-
obligation: find_best_leaf_obligation(infcx, &obligation),
140+
obligation: find_best_leaf_obligation(infcx, &obligation, true),
141141
code: FulfillmentErrorCode::Ambiguity { overflow: Some(true) },
142142
root_obligation: obligation,
143143
}));
@@ -198,7 +198,7 @@ fn fulfillment_error_for_no_solution<'tcx>(
198198
infcx: &InferCtxt<'tcx>,
199199
root_obligation: PredicateObligation<'tcx>,
200200
) -> FulfillmentError<'tcx> {
201-
let obligation = find_best_leaf_obligation(infcx, &root_obligation);
201+
let obligation = find_best_leaf_obligation(infcx, &root_obligation, false);
202202

203203
let code = match obligation.predicate.kind().skip_binder() {
204204
ty::PredicateKind::Clause(ty::ClauseKind::Projection(_)) => {
@@ -266,7 +266,7 @@ fn fulfillment_error_for_stalled<'tcx>(
266266
});
267267

268268
FulfillmentError {
269-
obligation: find_best_leaf_obligation(infcx, &obligation),
269+
obligation: find_best_leaf_obligation(infcx, &obligation, true),
270270
code,
271271
root_obligation: obligation,
272272
}
@@ -275,19 +275,21 @@ fn fulfillment_error_for_stalled<'tcx>(
275275
fn find_best_leaf_obligation<'tcx>(
276276
infcx: &InferCtxt<'tcx>,
277277
obligation: &PredicateObligation<'tcx>,
278+
consider_ambiguities: bool,
278279
) -> PredicateObligation<'tcx> {
279280
let obligation = infcx.resolve_vars_if_possible(obligation.clone());
280281
infcx
281282
.visit_proof_tree(
282283
obligation.clone().into(),
283-
&mut BestObligation { obligation: obligation.clone() },
284+
&mut BestObligation { obligation: obligation.clone(), consider_ambiguities },
284285
)
285286
.break_value()
286287
.unwrap_or(obligation)
287288
}
288289

289290
struct BestObligation<'tcx> {
290291
obligation: PredicateObligation<'tcx>,
292+
consider_ambiguities: bool,
291293
}
292294

293295
impl<'tcx> BestObligation<'tcx> {
@@ -355,11 +357,11 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
355357
}
356358
}
357359

358-
// Skip nested goals that hold.
359-
//FIXME: We should change the max allowed certainty based on if we're
360-
// visiting an ambiguity or error obligation.
361-
if matches!(nested_goal.result(), Ok(Certainty::Yes)) {
362-
continue;
360+
// Skip nested goals that aren't the *reason* for our goal's failure.
361+
match self.consider_ambiguities {
362+
true if matches!(nested_goal.result(), Ok(Certainty::Maybe(_))) => {}
363+
false if matches!(nested_goal.result(), Err(_)) => {}
364+
_ => continue,
363365
}
364366

365367
self.with_derived_obligation(obligation, |this| nested_goal.visit_with(this))?;

‎tests/ui/traits/next-solver/cycles/coinduction/incompleteness-unstable-result.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -61,7 +61,7 @@ where
6161
// entering the cycle from `A` fails, but would work if we were to use the cache
6262
// result of `B<X>`.
6363
impls_trait::<A<X>, _, _, _>();
64-
//~^ ERROR the trait bound `X: IncompleteGuidance<_, _>` is not satisfied
64+
//~^ ERROR the trait bound `A<X>: Trait<i32, u8, u8>` is not satisfied
6565
}
6666

6767
fn main() {

‎tests/ui/traits/next-solver/cycles/coinduction/incompleteness-unstable-result.stderr

+12-10
Original file line numberDiff line numberDiff line change
@@ -1,26 +1,28 @@
1-
error[E0277]: the trait bound `X: IncompleteGuidance<_, _>` is not satisfied
1+
error[E0277]: the trait bound `A<X>: Trait<i32, u8, u8>` is not satisfied
22
--> $DIR/incompleteness-unstable-result.rs:63:19
33
|
44
LL | impls_trait::<A<X>, _, _, _>();
5-
| ^^^^ the trait `IncompleteGuidance<_, _>` is not implemented for `X`, which is required by `A<X>: Trait<_, _, _>`
5+
| ^^^^ the trait `Trait<i32, u8, u8>` is not implemented for `A<X>`, which is required by `A<X>: Trait<_, _, _>`
66
|
7-
= help: the following other types implement trait `IncompleteGuidance<T, V>`:
8-
<T as IncompleteGuidance<U, i16>>
9-
<T as IncompleteGuidance<U, i8>>
10-
<T as IncompleteGuidance<U, u8>>
11-
note: required for `A<X>` to implement `Trait<_, _, u8>`
7+
note: required for `A<X>` to implement `Trait<i32, u8, u8>`
128
--> $DIR/incompleteness-unstable-result.rs:32:50
139
|
1410
LL | impl<T: ?Sized, U: ?Sized, V: ?Sized, D: ?Sized> Trait<U, V, D> for A<T>
1511
| ^^^^^^^^^^^^^^ ^^^^
16-
LL | where
17-
LL | T: IncompleteGuidance<U, V>,
18-
| ------------------------ unsatisfied trait bound introduced here
12+
...
13+
LL | A<T>: Trait<U, D, V>,
14+
| -------------- unsatisfied trait bound introduced here
15+
= note: 8 redundant requirements hidden
16+
= note: required for `A<X>` to implement `Trait<i32, u8, u8>`
1917
note: required by a bound in `impls_trait`
2018
--> $DIR/incompleteness-unstable-result.rs:51:28
2119
|
2220
LL | fn impls_trait<T: ?Sized + Trait<U, V, D>, U: ?Sized, V: ?Sized, D: ?Sized>() {}
2321
| ^^^^^^^^^^^^^^ required by this bound in `impls_trait`
22+
help: consider extending the `where` clause, but there might be an alternative better way to express this requirement
23+
|
24+
LL | X: IncompleteGuidance<u32, i16>, A<X>: Trait<i32, u8, u8>
25+
| ~~~~~~~~~~~~~~~~~~~~~~~~~~
2426

2527
error: aborting due to 1 previous error
2628

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