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Rollup merge of #92248 - compiler-errors:normalize-type-for-pointee, r=jackh726

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Normalize struct tail type when checking Pointee trait

Let's go ahead and implement the FIXMEs by properly normalizing the struct-tail type when satisfying a Pointee obligation. This should fix the ICE when we try to calculate a layout depending on `<Ty as Pointee>::Metadata` later.
Fixes #92128
Fixes #92577

Additionally, mark the obligation as ambiguous if there are any infer types in that struct-tail type. This has the effect of causing `<_ as Pointee>::Metadata` to be properly replaced with an infer variable ([here](https://github.com/rust-lang/rust/blob/master/compiler/rustc_trait_selection/src/traits/project.rs#L813)) and registered as an obligation... this turns out to be very important in unifying function parameters with formals that are assoc types.

Fixes #91446
This commit is contained in:
Matthias Krüger 2022-01-10 11:03:03 +01:00 • committed by GitHub
commit 6466f89fc5
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4 changed files with 61 additions and 10 deletions
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38
compiler/rustc_trait_selection/src/traits/project.rs
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@ -1400,8 +1400,17 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
// Any type with multiple potential metadata types is therefore not eligible.
let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty());
// FIXME: should this normalize?
let tail = selcx.tcx().struct_tail_without_normalization(self_ty);
let tail = selcx.tcx().struct_tail_with_normalize(self_ty, |ty| {
normalize_with_depth(
selcx,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
ty,
)
.value
});
match tail.kind() {
ty::Bool
| ty::Char
@ -1435,7 +1444,12 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
| ty::Bound(..)
| ty::Placeholder(..)
| ty::Infer(..)
| ty::Error(_) => false,
| ty::Error(_) => {
if tail.has_infer_types() {
candidate_set.mark_ambiguous();
}
false
},
}
}
super::ImplSource::Param(..) => {
@ -1640,18 +1654,30 @@ fn confirm_pointee_candidate<'cx, 'tcx>(
_: ImplSourcePointeeData,
) -> Progress<'tcx> {
let tcx = selcx.tcx();
let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty());
let substs = tcx.mk_substs([self_ty.into()].iter());
let mut obligations = vec![];
let metadata_ty = self_ty.ptr_metadata_ty(tcx, |ty| {
normalize_with_depth_to(
selcx,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
ty,
&mut obligations,
)
});
let substs = tcx.mk_substs([self_ty.into()].iter());
let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, None);
let predicate = ty::ProjectionPredicate {
projection_ty: ty::ProjectionTy { substs, item_def_id: metadata_def_id },
ty: self_ty.ptr_metadata_ty(tcx),
ty: metadata_ty,
};
confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
.with_addl_obligations(obligations)
}
fn confirm_fn_pointer_candidate<'cx, 'tcx>(