interface I { function f() external; function g() external; } interface J { function f() external; } abstract contract A is I, J { function f() external override (I, J) {} function g() external override virtual; } abstract contract B is I { function f() external override virtual; function g() external override {} } contract C is A, B { } // ---- // TypeError: (342-364): Derived contract must override function "f". Function with the same name and parameter types defined in two or more base classes. // TypeError: (342-364): Derived contract must override function "g". Function with the same name and parameter types defined in two or more base classes.