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Prefer object candidates over impl candidates in new selection

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This commit is contained in:
Michael Goulet 2023-07-06 04:48:33 +00:00
parent bd8aabef31
commit 3acaa568c2
2 changed files with 21 additions and 0 deletions
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8
compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
View File

@ -173,10 +173,18 @@ fn candidate_should_be_dropped_in_favor_of<'tcx>(
victim_idx >= other_idx
}
(_, CandidateSource::ParamEnv(_)) => true,
(
CandidateSource::BuiltinImpl(BuiltinImplSource::Object),
CandidateSource::BuiltinImpl(BuiltinImplSource::Object),
) => false,
(_, CandidateSource::BuiltinImpl(BuiltinImplSource::Object)) => true,
(CandidateSource::Impl(victim_def_id), CandidateSource::Impl(other_def_id)) => {
tcx.specializes((other_def_id, victim_def_id))
&& other.result.value.certainty == Certainty::Yes
}
_ => false,
}
}

13
tests/ui/traits/new-solver/dyn-any-dont-prefer-impl.rs Normal file
View File

@ -0,0 +1,13 @@
// compile-flags: -Ztrait-solver=next
// check-pass
use std::any::Any;
fn needs_usize(_: &usize) {}
fn main() {
let x: &dyn Any = &1usize;
if let Some(x) = x.downcast_ref::<usize>() {
needs_usize(x);
}
}