[clang] [clang] Add test for CWG110 "Can template functions and classes be declared in the same scope?" (PR #111446)

[Richard Smith via cfe-commits]

================
@@ -119,6 +119,16 @@ namespace cwg109 { // cwg109: yes
   };
 }
 
+namespace cwg110 { // cwg110: 2.8
+template <typename>
+void f();
+
+class f;
+
+template <typename>
+void f(int);
+} // namespace cwg110
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zygoloid wrote:

It'd be nice to also check that `class f` works here, and that uses of plain `f` name the function template.

https://github.com/llvm/llvm-project/pull/111446