[clang] [clang] Allow `$` in identifiers during preprocessing (PR #200614)

[Matthias Wippich via cfe-commits]

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+// RUN: %clang_cc1 %s -verify -fsyntax-only -fno-dollars-in-identifiers
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Tsche wrote:

It occurred to me that `-fno-dollars-in-macros` can result in rather odd behavior when _not_ combined with `-fno-dollars-in-identifiers`.

Is it possible to have `-fno-dollars-in-macros` imply `-fno-dollars-in-identifiers` or would that be weird?

I'll add tests for the combination of both - that should yield the same diagnostics as before this change :)

https://github.com/llvm/llvm-project/pull/200614