[clang] [clang] Reject constexpr-unknown values as constant expressions more consistently (PR #129952)

[Timm Baeder via cfe-commits]

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@@ -154,3 +154,26 @@ int g() {
     static_assert(f(arr) == 5);
 }
 }
+
+namespace GH128409 {
+  int &ff();
+  int &x = ff(); // nointerpreter-note {{declared here}}
+  constinit int &z = x; // expected-error {{variable does not have a constant initializer}}
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tbaederr wrote:

If you end the comments in `\`, you don't need to add the `@-2` stuff.

https://github.com/llvm/llvm-project/pull/129952