Fix parsing of type-specifier-seq's. Types are syntactically allowed to be
defined here, but not semantically, so

  new struct S {};

is always ill-formed, even if there is a struct S in scope.

We also had a couple of bugs in ParseOptionalTypeSpecifier caused by it being
under-loved (due to it only being used in a few places) so merge it into
ParseDeclarationSpecifiers with a new DeclSpecContext. To avoid regressing, this
required improving ParseDeclarationSpecifiers' diagnostics in some cases. This
also required teaching ParseSpecifierQualifierList about constexpr... which
incidentally fixes an issue where we'd allow the constexpr specifier in other
bad places.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152549 91177308-0d34-0410-b5e6-96231b3b80d8
17 files changed