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This isn't the correct way to fix that. It should be fixed during MIR lowering, see the corresponding code in rustc: https://github.com/rust-lang/rust/blob/e71c0f1e3395b10a8c331317be1a5c107bdf7b2e/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs#L125-L163.
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When an enum variant discriminant initializer references another variant via a cast, e.g. `B = Foo::A as isize + 1` the previous implementation would lower `Foo::A` as a place and then extract its discriminant via `Rvalue::Discriminant`. This caused infinite recursion during consteval because evaluating the discriminant of one variant requires evaluating another. # Conflicts: # crates/hir-ty/src/mir/lower.rs
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This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
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Single-variant enum incorrectly evaluated to 0.
Previously enum-to-int casts were lowered as a plain
Rvalue::Cast, causing single-variant enums to evaluate to 0 instead of their corresponding discriminant value.Fixes enum discriminant handling in MIR lowering by extracting the discriminant before performing the integer cast. Prevents recursion in MIR evaluation by reading discriminant bytes directly when the owner is a variant of the same enum in
Rvalue::Discriminantbranch.Fixes #23148