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Auto merge of #118120 - compiler-errors:closure-kind, r=lcnr

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Remove `PredicateKind::ClosureKind`

We don't need the `ClosureKind` predicate kind -- instead, `Fn`-family trait goals are left as ambiguous, and we only need to make progress on `FnOnce` projection goals for inference purposes.

This is similar to how we do confirmation of `Fn`-family trait and projection goals in the new trait solver, which also doesn't use the `ClosureKind` predicate.

Some hacky logic is added in the second commit so that we can keep the error messages the same.
This commit is contained in:
bors 2023-11-22 21:09:01 +00:00
commit 1e9dda77b5
19 changed files with 53 additions and 102 deletions
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12
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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@ -821,11 +821,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
&mut self,
obligation: &PolyTraitObligation<'tcx>,
) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
let kind = self
.tcx()
.fn_trait_kind_from_def_id(obligation.predicate.def_id())
.unwrap_or_else(|| bug!("closure candidate for non-fn trait {:?}", obligation));
// Okay to skip binder because the args on closure types never
// touch bound regions, they just capture the in-scope
// type/region parameters.
@ -835,15 +830,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
};
let trait_ref = self.closure_trait_ref_unnormalized(obligation, args);
let mut nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
debug!(?closure_def_id, ?trait_ref, ?nested, "confirm closure candidate obligations");
nested.push(obligation.with(
self.tcx(),
ty::Binder::dummy(ty::PredicateKind::ClosureKind(closure_def_id, args, kind)),
));
Ok(nested)
}