[Clang] Remove explicit object from non member function. (llvm#148807)

To avoid crashing later (as we assume only member functions can have
explicit object parameters)

Fixes llvm#113185

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -953,6 +953,7 @@ Bug Fixes to C++ Support
 - Fix a bug where private access specifier of overloaded function not respected. (#GH107629)
 - Correctly handles calling an explicit object member function template overload set
   through its address (``(&Foo::bar<baz>)()``).
+- Fix a crash when using an explicit object parameter in a non-member function. (#GH113185)
 - Fix a crash when forming an invalid call to an operator with an explicit object member. (#GH147121)
 - Correctly handle allocations in the condition of a ``if constexpr``.(#GH120197) (#GH134820)
 - Fixed a crash when handling invalid member using-declaration in C++20+ mode. (#GH63254)

clang/lib/Sema/SemaType.cpp

@@ -4860,7 +4860,9 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
             S.Diag(First->getBeginLoc(),
                    diag::err_explicit_object_parameter_invalid)
                 << First->getSourceRange();
-
+          // Do let non-member function have explicit parameters
+          // to not break assumptions elsewhere in the code.
+          First->setExplicitObjectParameterLoc(SourceLocation());
           D.setInvalidType();
           AreDeclaratorChunksValid = false;
         }

clang/test/SemaCXX/cxx2b-deducing-this.cpp

@@ -1347,3 +1347,13 @@ int main() {
     // expected-note@#S3-f-cand2 {{candidate function not viable: no known conversion from 'S3' to 'int' for object argument}}
 }
 }
+
+namespace GH113185 {
+
+void Bar(this int) { // expected-note {{candidate function}}
+    // expected-error@-1 {{an explicit object parameter cannot appear in a non-member function}}
+    Bar(0);
+    Bar(); // expected-error {{no matching function for call to 'Bar'}}
+}
+
+}