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Auto merge of #107614 - compiler-errors:allow-elaborator-to-filter-only-super-traits, r=oli-obk

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Split implied and super predicate queries, then allow elaborator to filter only supertraits

Split the `super_predicates_of` query into a new `implied_predicates_of` query. The former now only returns the *real* supertraits of a trait alias, and the latter now returns the implied predicates (which include all of the `where` clauses of the trait alias). The behavior of these queries is identical for regular traits.

Now that the two queries are split, we can add a new filter method to the elaborator, `filter_only_self()`, which can be used in instances that we need only the *supertrait* predicates, such as during the elaboration used in closure signature deduction. This toggles the usage of `super_predicates_of` instead of `implied_predicates_of` during elaboration of a trait predicate.

This supersedes #104745, and fixes the four independent bugs identified in that PR.
Fixes #104719
Fixes #106238
Fixes #110023
Fixes #109514

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bors 2023-04-12 08:39:19 +00:00
commit 9be9b5e09a
28 changed files with 307 additions and 149 deletions
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5
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@ -505,7 +505,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
let tcx = self.tcx();
let own_bounds: FxIndexSet<_> =
bounds.iter().map(|bound| bound.with_self_ty(tcx, self_ty)).collect();
for assumption in elaborate(tcx, own_bounds.iter().copied()) {
for assumption in elaborate(tcx, own_bounds.iter().copied())
// we only care about bounds that match the `Self` type
.filter_only_self()
{
// FIXME: Predicates are fully elaborated in the object type's existential bounds
// list. We want to only consider these pre-elaborated projections, and not other
// projection predicates that we reach by elaborating the principal trait ref,