fix: Unresolved type variables shouldn't escape impl selection - #23072
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ChayimFriedman2 merged 1 commit intoAug 10, 2026
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I encountered this panic when trying to generate SCIP for the rhai crate. |
ChayimFriedman2
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find_matching_impl() called resolve_vars_if_possible(), but we rely on unresolved region inference variables not escaping. Ensure that we substitute these variables. Without this fix, we can panic when trying to resolve the variable in the wrong inference context. See the new unit test. This seems to have always been wrong, but the panic only started occurring due when libcore changed in rust-lang/rust#136006. AI disclosure: Code partly written by GPT-5 Codex. I've bisected and confirmed the repro, and reviewed all the code, but possibly there's a nicer place to fix this logic.
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Added a FIXME which I think describes the your comment accurately. |
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find_matching_impl() called resolve_vars_if_possible(), but we rely on unresolved region inference variables not escaping. Ensure that we substitute these variables.
Without this fix, we can panic when trying to resolve the variable in the wrong inference context. See the new unit test.
This seems to have always been wrong, but the panic only started occurring due when libcore changed in
rust-lang/rust#136006.
AI disclosure: Code partly written by GPT-5 Codex. I've bisected and confirmed the repro, and reviewed all the code, but possibly there's a nicer place to fix this logic.