[PATCH] D132918: [clang] Fix a crash in constant evaluation

[Ilya Biryukov via Phabricator via cfe-commits]

ilya-biryukov added a comment.

I was just passing by, but wanted to add more context from our investigation with @kadircet.
If variables with incomplete types appear inside non-template `constexpr` function this gets detected by a call to `CheckConstexprFunctionDefinition` inside `ActOnFinishFunctionBody`:

  if (!IsInstantiation && FD && FD->isConstexpr() && !FD->isInvalidDecl() &&
      !CheckConstexprFunctionDefinition(FD, CheckConstexprKind::Diagnose))
    FD->setInvalidDecl();

So the resulting `constexpr` function is marked as invalid and Clang does not attempt to evaluate its body.
However, `CheckConstexprFunctionDefinition` does not run for template function instantiation, so the `VarDecl` marked invalid ends up inside a valid `constexpr` function and Clang does run the evaluation.


Repository:
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  https://reviews.llvm.org/D132918/new/

https://reviews.llvm.org/D132918