================
@@ -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;
----------------
whisperity wrote:
> If the only constructor is for a static factory function, which is
> unaccessible by the derived class, then the derived class cannot be
> constructed either, right?
@isuckatcs I think you are right, at least I tried to give this some thought
(actually by trying to construct a counter-example).
```cpp
template <class T>
class Base
{
Base(int I) {}
protected:
static Base factory(int I) { return Base{I}; }
};
class Derived : public Base<Derived>
{
// Derived() : Base(0) {} // Does not work.
Derived() : Base(Base::factory(1)) {}
};
void test()
{
Derived D;
}
```
```
<source>:18:13: error: calling a private constructor of class 'Derived'
18 | Derived D;
| ^
<source>:13:5: note: implicitly declared private here
13 | Derived() : Base(Base::factory(1)) {}
| ^
```
https://github.com/llvm/llvm-project/pull/82403
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