[clang-tools-extra] [clang-tidy] Unsafe CRTP check (PR #82403)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,232 @@
+// RUN: %check_clang_tidy %s bugprone-unsafe-crtp %t
+
+namespace class_implicit_ctor {
+template <typename T>
+class CRTP {};
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: the implicit default constructor of the CRTP is publicly accessible [bugprone-unsafe-crtp]
+// CHECK-MESSAGES: :[[@LINE-2]]:7: note: consider making it private
+// CHECK-FIXES: CRTP() = default;
+
+class A : CRTP<A> {};
+} // namespace class_implicit_ctor
+
+namespace class_uncostructible {
+template <typename T>
+class CRTP {
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: the CRTP cannot be constructed from the derived class [bugprone-unsafe-crtp]
+// CHECK-MESSAGES: :[[@LINE-2]]:7: note: consider declaring the derived class as friend
+// CHECK-FIXES: friend T;
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PiotrZSL wrote:

boost::noncopyable may not be best example, but thing is that private constructor is not an issue, simply check shouldn't say, "hey you forget friend" because such class may have private constructor on purpose, for example to use an factory function or just to provide static methods.

https://github.com/llvm/llvm-project/pull/82403