Alternatives to `Base.promote_op(op, ::Type...)` for `op::Type`?

General Usage
6

That’s a bit of an odd requirement, though. After all, I can always implement my own type which is <: Number and have sin(::MyType) = "foo". I don’t think we can make any statements at all about the return type of a function over an abstract type.

julia> struct Foo <: Number
       end

julia> Base.sin(::Foo) = "hello"

julia> Base.promote_op(sin, Number)
Number

julia> sin(Foo())
"hello"