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Rollup merge of #103355 - compiler-errors:rpitit-default-check, r=oli-obk

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Handle return-position `impl Trait` in traits properly in `register_hidden_type`

The bounds that we get by calling `bound_explicit_item_bounds` from an RPITIT have projections, not opaques, but when we're *registering* an opaque, we want to treat it like an opaque.

Coincidentally fixes #102688 as well, which makes sense, since that was failing because we were inferring an opaque type to be equal to itself (opaque cycle error => "cannot resolve opaque type").

Fixes #103352

r? ```@oli-obk```
This commit is contained in:
Matthias Krüger 2022-10-23 08:14:31 +02:00 • committed by GitHub
commit ff689a1404
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7 changed files with 63 additions and 14 deletions
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14
compiler/rustc_infer/src/infer/opaque_types.rs
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@ -1,6 +1,7 @@
use crate::errors::OpaqueHiddenTypeDiag;
use crate::infer::{DefiningAnchor, InferCtxt, InferOk};
use crate::traits;
use hir::def::DefKind;
use hir::def_id::{DefId, LocalDefId};
use hir::{HirId, OpaqueTyOrigin};
use rustc_data_structures::sync::Lrc;
@ -549,7 +550,12 @@ impl<'tcx> InferCtxt<'tcx> {
ty_op: |ty| match *ty.kind() {
// We can't normalize associated types from `rustc_infer`,
// but we can eagerly register inference variables for them.
ty::Projection(projection_ty) if !projection_ty.has_escaping_bound_vars() => {
// FIXME(RPITIT): Don't replace RPITITs with inference vars.
ty::Projection(projection_ty)
if !projection_ty.has_escaping_bound_vars()
&& tcx.def_kind(projection_ty.item_def_id)
!= DefKind::ImplTraitPlaceholder =>
{
self.infer_projection(
param_env,
projection_ty,
@ -565,6 +571,12 @@ impl<'tcx> InferCtxt<'tcx> {
{
hidden_ty
}
// FIXME(RPITIT): This can go away when we move to associated types
ty::Projection(proj)
if def_id.to_def_id() == proj.item_def_id && substs == proj.substs =>
{
hidden_ty
}
_ => ty,
},
lt_op: |lt| lt,