OT/J Language Definition v1.3.1

<< §4.10.(d) Binding to a type parameter

§4.10.(e) Propagating type parameters

If a callin binding binds to a generic base method, any type parameter(s) of the base method must be propagated into the role method by declaring the callin binding with type parameters, too. By matching a type parameter of a base method with a type variable of the callin binding, this genericity is propagated through the callin binding.

class MyBase {
	<T> T getIt(T it) { return it; }
}
team class MyTeam {
	protected class MyRole playedBy MyBase {
		callin <U> U rm(U a) { return base.rm(a); }
		<U> U rm(U a) <- replace U getIt(U it);
	}
}

Explanation:

The callin binding declares a type parameter <U> which is used to match all occurrences of T in the signature of getIt. Thus the implementation of rm uses the type U in exactly the same generic way as getIt uses T.

<< §4.10.(d) Binding to a type parameter

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1	class MyBase {
2	<T> T getIt(T it) { return it; }
3	}
4	team class MyTeam {
5	protected class MyRole playedBy MyBase {
6	callin <U> U rm(U a) { return base.rm(a); }
7	<U> U rm(U a) <- replace U getIt(U it);
8	}
9	}