Incorrect type when using dot syntax for broadcasting, in Julia 0.4

[giordano]

Run the following code in Julia 0.4

using Compat
x = 0:10
typeof(@compat(sin.(x)))
# => Array{Any,1}

while I'd expect type Array{Float64,1}. This is a problem because, for example, fft doesn't work with Array{Any}. It happens only if the argument is a named variable, @compat(sin.(0:10)) works as expected.

[stevengj]

The type computation in broadcast got improved in 0.5 ...

Maybe @compat(f.(x)) should look and see whether f is one of the list of built-in "vectorized" functions in 0.4 (sin etc. — see JuliaLang/julia#17302 for a list), and if so just call f(x).

[giordano]

But in Julia 0.4 this returns the correct type:

typeof(broadcast(sin, 0.0:10.0))
# => Array{Float64,1}
x = 0.0:10.0
typeof(broadcast(sin, x))
# => Array{Float64,1}

May it be a problem with parsing the named variable within the macro?

[yuyichao]

This is not fixable without actually backporting a significant amount of 0.5 code back to 0.4 in Compat. The broadcast syntax compat uses the same algorithm (well, it directly uses) for comprehension so the return type is as good as that. If you make x a local or a const the problem will be gone.