[clang] [clang] Avoid MS RTTI type_info name explosion (PR #206317)

[via cfe-commits]

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@@ -963,7 +970,9 @@ void MicrosoftCXXNameMangler::mangleName(GlobalDecl GD) {
   // Always start with the unqualified name.
   mangleUnqualifiedName(GD);
 
-  mangleNestedName(GD);
+  const auto *RD = dyn_cast<CXXRecordDecl>(GD.getDecl());
+  if (!ShortenRTTINames || !RD || !RD->isLambda())
+    mangleNestedName(GD);
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mzukovec wrote:

This was an old debugging remnant and unnecessary - the source of this change was that each level's lambda context re-spells the enclosing make_layer<T> where T is the previous level's full pack<..., lambda, ...>.

I cleaned the PR and audited it with Fable 5 just in case. It should be a simple change now that still resolves the bloat issue.

https://github.com/llvm/llvm-project/pull/206317