The crash was introduced by D83183 (f63e3ea558bb) as far as I can tell.
The problem is that ParenListExprs have a <NULL TYPE> which the
expression evaluation, specifically Expr::EvaluateAsInitializer,
couldn't deal with. One solution would have been to make the evaluation
logic capable of dealing with NULL TYPE, but I rather decided to
harmonize ParenListExprs with InitListExprs, which always have a void
type by default.
Actually I think that the dependent type would not be a bad fit here:
although the type of the contained expression might not be dependent,
the type of the expression itself might be. But this seems like a bigger
change, the assumption that InitListExprs have void type seems to be
baked into quite a few places.