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Rollup merge of #109896 - Nilstrieb:integers-are-not-fn-ptrs-remember-this-dear-transmuter, r=compiler-errors

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Never consider int and float vars for `FnPtr` candidates

This solves a regression where `0.0.cmp()` was ambiguous when a custom trait with a `cmp` method was in scope.

For integers it shouldn't be a problem in practice so I wasn't able to add a test.

I'm not sure whether there could be more issues hidden in the shadows as mentioned in the issue, but this should at least fix the problematic regression immediately.

fixes #109892

r? oli-obk
This commit is contained in:
Yuki Okushi 2023-04-04 05:52:35 +09:00 committed by GitHub
commit 7d3207be97
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3 changed files with 24 additions and 8 deletions
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10
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View File

@ -998,8 +998,14 @@ fn assemble_candidates_for_fn_ptr_trait(
| ty::Alias(..) | ty::Alias(..)
| ty::Param(..) | ty::Param(..)
| ty::Bound(..) | ty::Bound(..)
| ty::Error(_) => {} | ty::Error(_)
ty::Infer(_) => { | ty::Infer(
ty::InferTy::IntVar(_)
| ty::InferTy::FloatVar(_)
| ty::InferTy::FreshIntTy(_)
| ty::InferTy::FreshFloatTy(_),
) => {}
ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)) => {
candidates.ambiguous = true; candidates.ambiguous = true;
} }
} }

12
compiler/rustc_trait_selection/src/traits/select/mod.rs
View File

@ -177,14 +177,14 @@ struct TraitObligationStack<'prev, 'tcx> {
} }
struct SelectionCandidateSet<'tcx> { struct SelectionCandidateSet<'tcx> {
// A list of candidates that definitely apply to the current /// A list of candidates that definitely apply to the current
// obligation (meaning: types unify). /// obligation (meaning: types unify).
vec: Vec<SelectionCandidate<'tcx>>, vec: Vec<SelectionCandidate<'tcx>>,
// If `true`, then there were candidates that might or might /// If `true`, then there were candidates that might or might
// not have applied, but we couldn't tell. This occurs when some /// not have applied, but we couldn't tell. This occurs when some
// of the input types are type variables, in which case there are /// of the input types are type variables, in which case there are
// various "builtin" rules that might or might not trigger. /// various "builtin" rules that might or might not trigger.
ambiguous: bool, ambiguous: bool,
} }

10
tests/ui/fn/fn-ptr-trait-int-float-infer-var.rs Normal file
View File

@ -0,0 +1,10 @@
// check-pass
trait MyCmp {
fn cmp(&self) {}
}
impl MyCmp for f32 {}
fn main() {
// Ensure that `impl<F: FnPtr> Ord for F` is never considered for int and float infer vars.
0.0.cmp();
}