[Sema] Don't permit dependent alignments on non-dependent typedef-names
A dependent alignment attribute (like __attribute__((aligned(...))) or
__declspec(align(...))) on a non-dependent typedef or using declaration
poses a considerable challenge: the type is _not_ dependent, the size
_may_ be dependent if the type is used as an array type, the alignment
_is_ dependent.
It is reasonable for a compiler to be able to query the size and
alignment of a complete type. Let's help that become an invariant.
This fixes PR22042.
Differential Revision: http://reviews.llvm.org/D8693
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@234280
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