[clang] `__noop` not marked as constexpr #102064 (PR #105983)

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+// RUN: %clang_cc1 -std=c++20 -fms-extensions %s
+// expected-no-diagnostics
+constexpr int x = []{ __noop; return 0; }();
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ofAlpaca wrote:

If adding ``RUN: %clang_cc1 %s -std=c++20 -fms-extensions`` at the top line of builtins.cpp, without using define/ifdef, other testcases will fail.
Could @cor3ntin kindly give me more hints to this?


https://github.com/llvm/llvm-project/pull/105983