no_combined_super_signature

Can't infer missing types in '{0}' from overridden methods: {1}.

The analyzer produces this diagnostic when there is a method declaration for which one or more types needs to be inferred, and those types can't be inferred because none of the overridden methods has a function type that is a supertype of all the other overridden methods, as specified by override inference.

The following code produces this diagnostic because the method m declared in the class C is missing both the return type and the type of the parameter a, and neither of the missing types can be inferred for it:

abstract class A {
  A m(String a);
}

abstract class B {
  B m(int a);
}

abstract class C implements A, B {
  m(a);
}

In this example, override inference can't be performed because the overridden methods are incompatible in these ways:

• Neither parameter type (String and int) is a supertype of the other.
• Neither return type is a subtype of the other.

If possible, add types to the method in the subclass that are consistent with the types from all the overridden methods:

abstract class A {
  A m(String a);
}

abstract class B {
  B m(int a);
}

abstract class C implements A, B {
  C m(Object a);
}

Unless stated otherwise, the documentation on this site reflects Dart 3.8.1. Page last updated on 2025-05-08. View source or report an issue.