Bitfields in class templates cause assertion failures - Regression from 878a24ee244a

[smeenai]

Bugzilla Link	44886
Resolution	FIXED
Resolved on	Feb 13, 2020 00:33
Version	10.0
OS	All
Blocks	#43900
CC	@efriedma-quic,@elizabethandrews,@zmodem,@slacka,@mibintc,@zygoloid,@rnk

Extended Description

$ cat reduced.cpp
template class C {
enum { K = 1 };
int i : K;
unsigned u() { return i; }
};

$ clang -cc1 -fsyntax-only reduced.cpp
clang: /home/smeenai/llvm-project/clang/lib/AST/ExprConstant.cpp:14529: bool clang::Expr::isIntegerConstantExpr(llvm::APSInt &, const clang::ASTContext &, clang::SourceLocation *, bool) const: Assertion `!isValueDependent() && "Expression evaluator can't be called on a de
pendent expression."' failed.

I bisected this to 878a24e, so it's a regression from 9 to 10.

[rnk]

Is this fixed by the pending patch?
https://reviews.llvm.org/D72242

[smeenai]

Yup, it's fixed by that. Thanks for the pointer.

I don't quite understand why the bitfield width in my example ends up being considered value-dependent, since it's an enum constant and should be independent of the templated type, but eh.

[efriedma-quic]

I don't quite understand why the bitfield width in my example ends up being
considered value-dependent

It's a bug (or at least, clang doesn't match the current standard).

The relevant rule here is "An id-expression is value-dependent if [...] it names a static data member that is a dependent member of the current instantiation and is not initialized in a member-declarator[...]". computeDeclRefDependence in clang/lib/AST/Expr.cpp is missing the "is not initialized in a member-declarator" check.

[zmodem]

Is this fixed by the pending patch?
https://reviews.llvm.org/D72242

That landed, and I've cherry-picked it to 10.x as 808f8a6

Please let me know if there are any follow-ups.