There's nothing in the language that forces convert(T,x) to return
something of type T, so type inference has no idea what type b is. The
method that implements Float32(x) is this:
call{T}(::Type{T}, arg) = convert(T, arg)::T
Note the type assertion – so type inference does know the type of the
result. Related: #1090 <https://github.com/JuliaLang/julia/issues/1090>.
On Mon, Jun 1, 2015 at 5:06 PM, Arch Robison <arch.d.robi...@gmail.com>
wrote:
> I was a bit surprised when I tried this example:
> function foo()
> global G
> #b = Float32(G)
> b = convert(Float32,G)
> b
> end
>
> G = 0.5
> println(foo())
> code_warntype(foo,())
> and code_warntype deduced that the type of b is ANY instead of Float32.
> Is this a bug or a feature? If I use the constructor syntax instead (see
> comment in code), then the type of b is deduced as Float32.
>
