[clang] Don't wrap immediate invocations in ConstantExprs within constexpr initializers (PR #89565)

[Daniel M. Katz via cfe-commits]

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@@ -244,8 +244,8 @@ namespace UndefinedBehavior {
     constexpr int n13 = n5 + n5; // expected-error {{constant expression}} expected-note {{value -4294967296 is outside the range of }}
     constexpr int n14 = n3 - n5; // expected-error {{constant expression}} expected-note {{value 4294967295 is outside the range of }}
     constexpr int n15 = n5 * n5; // expected-error {{constant expression}} expected-note {{value 4611686018427387904 is outside the range of }}
-    constexpr signed char c1 = 100 * 2; // ok expected-warning{{changes value}}
-    constexpr signed char c2 = '\x64' * '\2'; // also ok  expected-warning{{changes value}}
+    constexpr signed char c1 = 100 * 2; // ok - no error from changing value because initializer is constexpr.
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katzdm wrote:

I think the additional diagnostic is relatively harmless; I've gone ahead with the change I suggested above.

https://github.com/llvm/llvm-project/pull/89565