Reading the specification (https://go.googlesource.com/proposal/+/refs/heads/master/des...) this flows from the type being declared generic, Go will (currently at least) require the receiver to be similarly generic, no specialisation, and no method constraints:

> Generic types can have methods. The receiver type of a method must declare the same number of type parameters as are declared in the receiver type's definition. They are declared without any constraint.

    // Push adds a value to the end of a vector.
    func (v *Vector[T]) Push(x T) { *v = append(*v, x) }

> The type parameters listed in a method declaration need not have the same names as the type parameters in the type declaration. In particular, if they are not used by the method, they can be _.