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Rollup merge of #113741 - compiler-errors:rpitit-projects-to-missing-opaque, r=spastorino

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Don't install default projection bound for return-position `impl Trait` in trait methods with no body

This ensures that we never try to project to an opaque type in a trait method that has no body to infer its hidden type, which means we never later call `type_of` on that opaque. This is because opaque types try to reveal their hidden type when proving auto traits.

I thought about this a lot, and I think this is a fix that's less likely to introduce other strange downstream ICEs than #113461.

Fixes #113434

r? `@spastorino`
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Jubilee 2023-07-30 17:50:48 -07:00 • committed by GitHub
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4 changed files with 30 additions and 8 deletions
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8
compiler/rustc_metadata/src/rmeta/encoder.rs
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@ -1144,13 +1144,7 @@ fn should_encode_type(tcx: TyCtxt<'_>, def_id: LocalDefId, def_kind: DefKind) ->
let assoc_item = tcx.associated_item(def_id);
match assoc_item.container {
ty::AssocItemContainer::ImplContainer => true,
// Always encode RPITITs, since we need to be able to project
// from an RPITIT associated item to an opaque when installing
// the default projection predicates in default trait methods
// with RPITITs.
ty::AssocItemContainer::TraitContainer => {
assoc_item.defaultness(tcx).has_value() || assoc_item.is_impl_trait_in_trait()
}
ty::AssocItemContainer::TraitContainer => assoc_item.defaultness(tcx).has_value(),
}
}
DefKind::TyParam => {