Cobra Forums

Hi. Quick one. What's the syntax for declaring a new constraint?

Code: Select all

def method<of T>
    where T must be XXX
    t = T() # error: Cannot create an instance of the variable
            # type "T" because it doesn"t have the new() constraint
    ...


rumour has it that you use callable

Code: Select all

class G1<of TArg>
        where TArg must be class, callable

        cue init
                base.init
                a = TArg()  # instantiate a generic parameter
                b = TArg()
                assert a is not b
                assert a.getHashCode
                assert b.getHashCode


see Tests/240-generics/300-declare-generic-classes/602-instantiate-generic-arg.cobra
and new constraint search

This stuff should be in the (NYI) wiki pages on generics