Shouldn't this throw an error?

I have inadvertently made this mistake:

F(x, f::F) where F = f(x)

julia> F(0.5, sin)
ERROR: MethodError: no method matching F(::Float64, ::typeof(sin))

Shouldn’t the first line throw and error or are there cases where that is useful?

I don’t see why we’d need to prohibit something like:

foo(x, ::typeof(foo)) = 3x
foo(x, g::G) where {G} = g(x)
foo(2, foo)
foo(2, abs2)

Wrong answer, see below.

Maybe I shouldn’t answer questions at 3am. Obviously ::F isn’t the same as ::typeof(F).


the code with F twice doesn’t actually create a method:

julia> F(x, f::F) where F = f(x)
F (generic function with 0 methods)