[clang] [CIR] Add undef handling to enable global lambdas (PR #169721)

[Henrich Lauko via cfe-commits]

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@@ -330,6 +330,12 @@ static LogicalResult checkConstantTypes(mlir::Operation *op, mlir::Type opType,
         "zero expects struct, array, vector, or complex type");
   }
 
+  if (isa<cir::UndefAttr>(attrType)) {
+    if (!::mlir::isa<cir::VoidType>(opType))
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xlauko wrote:

or add `mlir::`​ in both cases here?

https://github.com/llvm/llvm-project/pull/169721