Amiguity warning

[daviddelaat]

The following code which doesn't seem ambiguous to me gives an ambiguity warning:

type A{T}; end
type B{T}; end

f{T}(::T, ::A{T}) = 1
f{T}(::B{T}, ::T) = 2

[StefanKarpinski]

What if the first T is B and the second T is A? Then you get

f(::B, ::A{B}) = 1
f(::B{A}, ::A) = 2

The intersection case is f(::B{A}, ::A{B}).

[daviddelaat]

But you can't just substitute an abstract type for T right?
For instance, if I define

g{T}(::T, ::T) = 1

then there is no method g(::Array, ::Array) = 1 because I can't call g([1], [1.0]).

[StefanKarpinski]

A{B} and B{A} are concrete types and A{B} <: A and B{A} <: B, hence the ambiguity.

[JeffBezanson]

Duplicate of #1631

[daviddelaat]

Aah, sorry about that, hadn't seen the other issue.