Make parametric stagedfunctions work better

[timholy]

h gives what one wants, but it's not as pretty as it should be.

stagedfunction f{T<:FloatingPoint}(a::Vector{T})
    @show a
    :(println($T))
end

stagedfunction g(a::Vector)
    T = eltype(a)
    @show a
    :(println($T))
end

stagedfunction h{T<:FloatingPoint}(a::Vector{T})
    TT = eltype(a)
    @show a
    :(println($TT))
end

Test:

julia> include("/tmp/params.jl")
h (generic function with 1 method)

julia> af = [1.0,2.0]
2-element Array{Float64,1}:
 1.0
 2.0

julia> ai = [1,2]
2-element Array{Int64,1}:
 1
 2

julia> f(af)
a = Array{Float64,1}
ERROR: T not defined
 in f at /tmp/params.jl:3

julia> g(af)
a = Array{Float64,1}
Float64

julia> h(af)
a = Array{Float64,1}
Float64

julia> f(ai)
ERROR: `f` has no method matching f(::Array{Int64,1})

julia> g(ai)
a = Array{Int64,1}
Int64

julia> h(ai)
ERROR: `h` has no method matching h(::Array{Int64,1})

[timholy]

Unfortunately, on #8501 I used up a little more time than I actually had available to work on julia-core projects, so I'm not going to get to these for a little while.

[Jutho]

Thanks for this, however, I noticed a bug if the parameters in the function specification does not match the order in which they appear in the arguments. That is:

stagedfunction foo1{N,T}(a::Array{T,N})
    println("N = $N, T = $T")
    return :a
end

stagedfunction foo2{T,N}(a::Array{T,N})
    println("N = $N, T = $T")
    return :a
end

foo1(randn(3,3));  # => N = Float64, T = 2
foo2(randn(3,3)); #=> N = 2, T = Float64

[Jutho]

Thanks for fixing this

[timholy]

👍