[julia-users] Type inference cannot deduce that convert(Float32,x) returns a Float32?

[Arch Robison]

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.