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Auto merge of #95315 - compiler-errors:pointee-fix, r=pnkfelix

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when checking pointee metadata, canonicalize the `Sized` check

Use `infcx.predicate_must_hold_modulo_regions` with a `Sized` obligation instead of just calling `ty.is_sized`, because the latter does not canonicalize region and type vars (and in the test case I added in this PR, there's a region var in the `ParamEnv`).

Fixes #95311
This commit is contained in:
bors 2022-04-14 14:37:34 +00:00
commit e7575f9670
2 changed files with 30 additions and 1 deletions
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12
compiler/rustc_trait_selection/src/traits/project.rs
View File

@ -19,6 +19,7 @@ use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey};
use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
use crate::traits::error_reporting::InferCtxtExt as _;
use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use crate::traits::select::ProjectionMatchesProjection;
use rustc_data_structures::sso::SsoHashSet;
use rustc_data_structures::stack::ensure_sufficient_stack;
@ -1562,7 +1563,16 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
// type parameters, opaques, and unnormalized projections have pointer
// metadata if they're known (e.g. by the param_env) to be sized
ty::Param(_) | ty::Projection(..) | ty::Opaque(..)
if tail.is_sized(selcx.tcx().at(obligation.cause.span), obligation.param_env) =>
if selcx.infcx().predicate_must_hold_modulo_regions(
&obligation.with(
ty::Binder::dummy(ty::TraitRef::new(
selcx.tcx().require_lang_item(LangItem::Sized, None),
selcx.tcx().mk_substs_trait(self_ty, &[]),
))
.without_const()
.to_predicate(selcx.tcx()),
),
) =>
{
true
}

19
src/test/ui/traits/issue-95311.rs Normal file
View File

@ -0,0 +1,19 @@
// check-pass
// Test to check that pointee trait doesn't let region variables escape into the cache
#![feature(ptr_metadata)]
trait Bar: Sized + 'static {}
struct Foo<B: Bar> {
marker: std::marker::PhantomData<B>,
}
impl<B: Bar> Foo<B> {
fn foo<T: ?Sized>(value: &T) {
std::ptr::metadata(value);
}
}
fn main() {}