[PATCH] D138210: [clang] Require parameter pack to be last argument in concepts.

[Luke Nihlen via Phabricator via cfe-commits]

luken-google added a comment.

There is logic in the template expansion that returns an error state if the template parameter pack was not at the end of the template parameter list. It returns `true` but does not generate any diagnostics, but the outer code error machinery assumes that diagnostics have already been generated and so considers the expression invalid and moves on.

As this fix no longer accepts these ill-formed templates as valid, that code no longer fires. I have strengthened the check there to an assert. PTAL.


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https://reviews.llvm.org/D138210