isCovariantWith

Determines whether the function type F is covariant with G, i.e., functions of the type F can override ones of the type G.

template isCovariantWith (

) if (

is(F == function) &&

is(G == function)

is(F == delegate) &&

is(G == delegate)

isFunctionPointer!F &&

isFunctionPointer!G

) {

static if(is(F : G))

enum isCovariantWith;

static if(!(is(F : G)))

enum isCovariantWith;

}

Examples

interface I { I clone(); }
interface J { J clone(); }
class C : I
{
    override C clone()   // covariant overriding of I.clone()
    {
        return new C;
    }
}

// C.clone() can override I.clone(), indeed.
static assert(isCovariantWith!(typeof(C.clone), typeof(I.clone)));

// C.clone() can't override J.clone(); the return type C is not implicitly
// convertible to J.
static assert(!isCovariantWith!(typeof(C.clone), typeof(J.clone)));

isCovariantWith

Examples

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