[clang] [clang] Remove separate evaluation step for static class member init. (PR #142713)

[Shafik Yaghmour via cfe-commits]

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@@ -143,3 +143,8 @@ namespace fold_initializer {
   const float A::f = __builtin_is_constant_evaluated();
   static_assert(fold(A::f == 1.0f));
 }
+
+struct GH99680 {
+  static const int x = 1/(1-__builtin_is_constant_evaluated()); // expected-error {{in-class initializer for static data member is not a constant expression}} \
+    // expected-note {{division by zero}}
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shafik wrote:

So if this is constant evaluated we have UB (divide by zero) so then it can't be constant evaluated and therefore `__builtin_is_constant_evaluated()` must be zero and therefore no divide by zero.

Which is the same logic used in the example in *[expr.const]p28.5*

https://github.com/llvm/llvm-project/pull/142713