[clang] [HLSL] Add diagnostic for enabling 16 bit types (PR #84537)

[Damyan Pepper via cfe-commits]

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@@ -243,6 +243,20 @@ HLSLToolChain::TranslateArgs(const DerivedArgList &Args, StringRef BoundArch,
   // FIXME: add validation for enable_16bit_types should be after HLSL 2018 and
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damyanp wrote:

Is this FIXME comment outdated by this PR?

https://github.com/llvm/llvm-project/pull/84537