[clang] [clang] Diagnose default arguments defined in different scopes (PR #124844)

[via cfe-commits]

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@@ -5145,6 +5145,10 @@ def err_addr_ovl_not_func_ptrref : Error<
 def err_addr_ovl_no_qualifier : Error<
   "cannot form member pointer of type %0 without '&' and class name">;
 
+def err_ovl_ambiguous_default_arg
+    : Error<"function call relies on ambiguous default argument %select{|for "
+            "parameter '%1'}0">;
+
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cor3ntin wrote:

```suggestion
def err_ovl_ambiguous_default_arg : Error<
    "ambiguous default argument %select{|for parameter '%1'}0">;

```

https://github.com/llvm/llvm-project/pull/124844