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Auto merge of #117878 - gavinleroy:proper-depth-check, r=lcnr

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Fix depth check in ProofTreeVisitor.

The hack to cutoff overflows and cycles in the new trait solver was incorrect. We want to inspect everything with depth [0..10].

This fix exposed a previously unseen bug, which caused the compiler to ICE when invoking `trait_ref` on a non-assoc type projection. I simply added the guard in the `AmbiguityCausesVisitor`, and updated the expected output for the `auto-trait-coherence` test which now includes the extra note:
```text
   |
   = note: upstream crates may add a new impl of trait `std::marker::Send` for type `OpaqueType` in future versions
```

r? `@lcnr`
This commit is contained in:
bors 2023-11-15 18:53:04 +00:00
commit 6b771f6b5a
3 changed files with 10 additions and 2 deletions
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2
compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
View File

@ -58,7 +58,7 @@ impl<'a, 'tcx> InspectCandidate<'a, 'tcx> {
visitor: &mut V,
) -> ControlFlow<V::BreakTy> {
// HACK: An arbitrary cutoff to avoid dealing with overflow and cycles.
if self.goal.depth >= 10 {
if self.goal.depth <= 10 {
let infcx = self.goal.infcx;
infcx.probe(|_| {
let mut instantiated_goals = vec![];

8
compiler/rustc_trait_selection/src/traits/coherence.rs
View File

@ -20,6 +20,7 @@ use crate::traits::{
};
use rustc_data_structures::fx::FxIndexSet;
use rustc_errors::Diagnostic;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LOCAL_CRATE};
use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, TyCtxtInferExt};
use rustc_infer::traits::{util, TraitEngine};
@ -1002,7 +1003,12 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a> {
// and then prove the resulting predicate as a nested goal.
let trait_ref = match predicate.kind().no_bound_vars() {
Some(ty::PredicateKind::Clause(ty::ClauseKind::Trait(tr))) => tr.trait_ref,
Some(ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj))) => {
Some(ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)))
if matches!(
infcx.tcx.def_kind(proj.projection_ty.def_id),
DefKind::AssocTy | DefKind::AssocConst
) =>
{
proj.projection_ty.trait_ref(infcx.tcx)
}
_ => return ControlFlow::Continue(()),

2
tests/ui/impl-trait/auto-trait-coherence.next.stderr
View File

@ -6,6 +6,8 @@ LL | impl<T: Send> AnotherTrait for T {}
...
LL | impl AnotherTrait for D<OpaqueType> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `D<OpaqueType>`
|
= note: upstream crates may add a new impl of trait `std::marker::Send` for type `OpaqueType` in future versions
error: aborting due to previous error