[clang] [Clang] Reapply CWG2369 "Ordering between constraints and substitution" (PR #122423)

[via cfe-commits]

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@@ -8058,6 +8059,54 @@ bool Sema::CheckNonDependentConversions(
     }
   }
 
+  // A heuristic & speculative workaround for bug
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99599 that manifests after
+  // CWG2369.
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cor3ntin wrote:

I think that we should simplify that to just "has user-defined conversion operator" - I think both GCC folks and @zygoloid agree this is a simpler direction

https://github.com/llvm/llvm-project/pull/122423