stagedfunction called with Any

[mlubin]

I thought it was guaranteed that staged functions would be called with concrete types, but the following code seems to trick Julia into calling a stagedfunction with Any:

stagedfunction foo(t)
    @show t
    return
end

x = Array(Float64, 5)

let
    x = Array(Int,3)
    for i in 1:3
        x[i] = i
    end
    foo(x[1])

end

prints

t = Any
t = Any

This behavior is highly sensitive to the structure, if you remove let or the assignment to x[i], then the function is called correctly with Int.

CC @Keno @timholy

julia> versioninfo()
Julia Version 0.4.0-dev+812
Commit a28d619 (2014-09-27 07:46 UTC)
Platform Info:
  System: Linux (x86_64-linux-gnu)
  CPU: Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Sandybridge)
  LAPACK: libopenblas
  LIBM: libopenlibm
  LLVM: libLLVM-3.3

[Keno]

You can throw an error in the staged function if the type is too general for you which will have it fall back to runtime dispatch.

[mlubin]

Ah, useful to document :)

[timholy]

Related: #8504.

[timholy]

@Keno, actually, if this works, why does #8504 happen?