Merging rr285370:

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r285370 | rtrieu | 2016-10-27 17:15:24 -0700 (Thu, 27 Oct 2016) | 10 lines

Fix a crash on invalid code.

The diagnostic was attempting to access the QualType of a TypeDecl by calling
TypeDecl::getTypeForDecl.  However, the Type pointer stored there is lazily
loaded by functions in ASTContext.  In most cases, the pointer is loaded and
this does not cause a problem.  However, when more that 50 or so unknown types
are seen beforehand, this causes the Type to not be loaded, passing a null
Type to the diagnostics, leading to the crash.  Using
ASTContext::getTypeDeclType will give a proper QualType for all cases.

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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_39@286923 91177308-0d34-0410-b5e6-96231b3b80d8