defining the choice of overload when more than one applies

[ashleyh]

I don't think it's completely clear what the following example should print:

class A: pass
class B(A): pass

def f(A a): print('A')
def f(B b): print('B')

f(B())

One might intuitively expect the 'best match' to be chosen, which would print 'B', but the current implementation actually chooses the 'first match', which would print 'A'. This isn't wrong per se but I think it's at least worth documenting.

[JukkaL]

Yes, the desired behaviour is to pick the first matching overload variant. It should be described in the documentation.

[JukkaL]

Ah, and the type checker should probably give a warning in cases like the above example, since the second overload can never be called.

[ashleyh]

By the way, the overview page says:

The most specific signature is selected at runtime at each call.

[JukkaL]

Oops, that's how I initially designed it, but it turned out to be a bad idea (often there is no single most specific signature). No it should be fixed in the overview.

[ashleyh]

Yeah, I agree that first match is a better idea, just wanted to point out the discrepancy in the docs.