[clang-tools-extra] Add check 'cppcoreguidelines-use-enum-class' (PR #138282)

[Carlos Galvez via cfe-commits]

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@@ -0,0 +1,50 @@
+// RUN: %check_clang_tidy -std=c++11-or-later %s cppcoreguidelines-use-enum-class %t
+
+enum E {};
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: enum 'E' is unscoped, use 'enum class' instead
+
+enum class EC {};
+
+struct S {
+  enum E {};
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: enum 'E' is unscoped, use 'enum class' instead
+  enum class EC {};
+};
+
+class C {
+  enum E {};
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: enum 'E' is unscoped, use 'enum class' instead
+  enum class EC {};
+};
+
+template<class T>
+class TC {
+  enum E {};
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: enum 'E' is unscoped, use 'enum class' instead
+  enum class EC {};
+};
+
+union U {
+  enum E {};
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: enum 'E' is unscoped, use 'enum class' instead
+  enum class EC {};
+};
+
+namespace {
+enum E {};
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: enum 'E' is unscoped, use 'enum class' instead
+enum class EC {};
+} // namespace
+
+namespace N {
+enum E {};
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: enum 'E' is unscoped, use 'enum class' instead
+enum class EC {};
+} // namespace N
+
+template<enum ::EC>
+static void foo();
+
+enum ForwardE : int;
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: enum 'ForwardE' is unscoped, use 'enum class' instead
+enum class ForwardEC : int;
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carlosgalvezp wrote:

It would be good to add a test with `enum struct` as well, Jason Turner shows that unconventional pattern a lot.

https://github.com/llvm/llvm-project/pull/138282