[clang] [clang] Diagnose problematic diagnostic messages (PR #93229)

[Erich Keane via cfe-commits]

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@@ -1302,7 +1302,8 @@ static void verifyDiagnosticWording(const Record &Diag) {
     // closing '}', skipping intermediary {} pairs.
 
     size_t BraceCount = 1;
-    auto Iter = FullDiagText.begin() + /*%select{*/ 8;
+    constexpr size_t PercentSelectBraceLen = sizeof("%select{") - 1;
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erichkeane wrote:

Even better :) 

https://github.com/llvm/llvm-project/pull/93229