[clang] clang: __builtin_VARIABLE_NAME (PR #86756)

[Jon Roelofs via cfe-commits]

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@@ -2305,6 +2308,36 @@ APValue SourceLocExpr::EvaluateInContext(const ASTContext &Ctx,
   };
 
   switch (getIdentKind()) {
+  case SourceLocIdentKind::VariableName: {
+    // __builtin_VARIABLE_NAME() is a Clang-specific extension that expands to
+    // the name of the variable being defined in a CXXDefaultArgExpr.
+
+    // FIXME: The AST doesn't have upward edges, so we can't easily traverse up
+    // from the CXXDefaultArgExpr to find it.  Unfortunately, this means we need
+    // to do a linear scan of (up to) the entire FunctionDecl.
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jroelofs wrote:

I could use some help here. Using the visitor to walk back up the AST feels wrong / slow.

https://github.com/llvm/llvm-project/pull/86756