diff options
3 files changed, 52 insertions, 9 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs index 7ca33ae41c0..16e44c0006a 100644 --- a/compiler/rustc_trait_selection/src/traits/coherence.rs +++ b/compiler/rustc_trait_selection/src/traits/coherence.rs @@ -408,7 +408,7 @@ fn impl_intersection_has_negative_obligation( // Equate the headers to find their intersection (the general type, with infer vars, // that may apply both impls). - let Some(_equate_obligations) = + let Some(equate_obligations) = equate_impl_headers(infcx, param_env, &impl1_header, &impl2_header) else { return false; @@ -416,6 +416,13 @@ fn impl_intersection_has_negative_obligation( plug_infer_with_placeholders(infcx, universe, (impl1_header.impl_args, impl2_header.impl_args)); + // FIXME(with_negative_coherence): the infcx has constraints from equating + // the impl headers. We should use these constraints as assumptions, not as + // requirements, when proving the negated where clauses below. + drop(equate_obligations); + drop(infcx.take_registered_region_obligations()); + drop(infcx.take_and_reset_region_constraints()); + util::elaborate(tcx, tcx.predicates_of(impl2_def_id).instantiate(tcx, impl2_header.impl_args)) .any(|(clause, _)| try_prove_negated_where_clause(infcx, clause, param_env)) } @@ -541,14 +548,6 @@ fn try_prove_negated_where_clause<'tcx>( return false; }; - // FIXME(with_negative_coherence): the infcx has region contraints from equating - // the impl headers as requirements. Given that the only region constraints we - // get are involving inference regions in the root, it shouldn't matter, but - // still sus. - // - // We probably should just throw away the region obligations registered up until - // now, or ideally use them as assumptions when proving the region obligations - // that we get from proving the negative predicate below. let ref infcx = root_infcx.fork(); let ocx = ObligationCtxt::new(infcx); diff --git a/tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.explicit.stderr b/tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.explicit.stderr new file mode 100644 index 00000000000..34f3904443c --- /dev/null +++ b/tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.explicit.stderr @@ -0,0 +1,19 @@ +error: conflicting implementations of trait `FnMarker` for type `fn(&_)` + --> $DIR/negative-coherence-placeholder-region-constraints-on-unification.rs:21:1 + | +LL | impl<T: ?Sized + Marker> FnMarker for fn(T) {} + | ------------------------------------------- first implementation here +LL | impl<T: ?Sized> FnMarker for fn(&T) {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `fn(&_)` + | + = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! + = note: for more information, see issue #56105 <https://github.com/rust-lang/rust/issues/56105> + = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details +note: the lint level is defined here + --> $DIR/negative-coherence-placeholder-region-constraints-on-unification.rs:4:11 + | +LL | #![forbid(coherence_leak_check)] + | ^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to previous error + diff --git a/tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.rs b/tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.rs new file mode 100644 index 00000000000..26d9d84d8f0 --- /dev/null +++ b/tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.rs @@ -0,0 +1,25 @@ +// revisions: explicit implicit +//[implicit] check-pass + +#![forbid(coherence_leak_check)] +#![feature(negative_impls, with_negative_coherence)] + +pub trait Marker {} + +#[cfg(implicit)] +impl<T: ?Sized> !Marker for &T {} + +#[cfg(explicit)] +impl<'a, T: ?Sized + 'a> !Marker for &'a T {} + +trait FnMarker {} + +// Unifying these two impls below results in a `T: '!0` obligation +// that we shouldn't need to care about. Ideally, we'd treat that +// as an assumption when proving `&'!0 T: Marker`... +impl<T: ?Sized + Marker> FnMarker for fn(T) {} +impl<T: ?Sized> FnMarker for fn(&T) {} +//[explicit]~^ ERROR conflicting implementations of trait `FnMarker` for type `fn(&_)` +//[explicit]~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! + +fn main() {} |