[clang] [Clang] Mark declarators invalid in the presence of ill-formed explicit parameters. (PR #70018)

[Shafik Yaghmour via cfe-commits]

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@@ -542,3 +542,46 @@ void foo(C c) {
 }
 
 }
+
+
+namespace GH69838 {
+struct S {
+  S(this auto &self) {} // expected-error {{an explicit object parameter cannot appear in a constructor}}
+  virtual void f(this S self) {} // expected-error {{an explicit object parameter cannot appear in a virtual function}}
+  void g(this auto &self) const {} // expected-error {{explicit object member function cannot have 'const' qualifier}}
+  void h(this S self = S{}) {} // expected-error {{the explicit object parameter cannot have a default argument}}
+  void i(int i, this S self = S{}) {} // expected-error {{an explicit object parameter can only appear as the first parameter of the function}}
+  ~S(this S &&self); // expected-error {{an explicit object parameter cannot appear in a destructor}} \
+                     // expected-error {{destructor cannot have any parameters}}
+
+  static void j(this S s); // expected-error {{an explicit object parameter cannot appear in a static function}}
+};
+
+void nonmember(this S s); // expected-error {{an explicit object parameter cannot appear in a non-member function}}
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shafik wrote:

You could add `static` here for extra fun.

https://github.com/llvm/llvm-project/pull/70018