[libcxxabi] [llvm] Fix C++ demangling for _BitInt type (PR #143466)

[Larry Meadows via llvm-commits]

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@@ -4468,7 +4468,9 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
         return nullptr;
       if (!consumeIf('_'))
         return nullptr;
-      return make<BitIntType>(Size, Signed);
+      // The FE expects this to be available for Substitution
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lfmeadow wrote:

Yes, I meant front end. I will spell it out.

https://github.com/llvm/llvm-project/pull/143466