[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.
+    struct FindVarDecl : public RecursiveASTVisitor<FindVarDecl> {
+      const Expr *ToFind;
+      const VarDecl *Found = nullptr;
+      bool TraverseVarDecl(VarDecl *D) {
+        if (const auto *CE = dyn_cast_or_null<CXXConstructExpr>(D->getInit())) {
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jroelofs wrote:

Need to strip casts, conversions, parens, etc.

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