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

[Erich Keane via cfe-commits]

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@@ -9,8 +9,7 @@ using MaxBitInt = _BitInt(128);
 
 constexpr _BitInt(2) A = 0;
 constexpr _BitInt(2) B = A + 1;
-constexpr _BitInt(2) C = B + 1; // expected-warning {{from 2 to -2}} \
-                                // ref-warning {{from 2 to -2}}
+constexpr _BitInt(2) C = B + 1;
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erichkeane wrote:

Losing this diagnostic is definitely incorrect, this is one we should have kept.

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