type inference fails with more than 13 arguments

[Alexander-Barth]

The following function is type-unstable. However, if I just remove one of the parameters (positional or keyword), then the function becomes type stable. Is there a limit about the number of arguments ? 13 arguments are fine for type inference but not 14 or more.

function myfun(x,v::Vector{T},distbin,mincount;
               len::T = 1.,
               var0::T = 1.,
               minlen::T = 1e-5,
               maxlen::T = 10.,
               minvar0::T = 0.,
               maxvar0::T = 10.,
               tolrel::T = 1e-4,
               maxpoints::Int = 1000000,
               nmean::Int = 1,
               stdcovar::T = 1.
               ) where T

    pmax = length(distbin)
    distx = zeros(T,pmax)
    for i = 1:pmax
        distx[i] = distbin[i]
    end
    return distx
end

code_warntype myfun(1.,[1.],1:10,100)

produces:

Variables:
  #self#::#myfun
  x::Float64
  v::Array{Float64,1}
  distbin::UnitRange{Int64}
  mincount::Int64

Body:
  begin 
      return $(Expr(:invoke, MethodInstance for #myfun#6(::Float64, ::Float64, ::Float64, ::Float64, ::Float64, ::Float64, ::Float64, ::Int64, ::Int64, ::Float64, ::#myfun, ::Float64, ::Array{Float64,1}, ::UnitRange{Int64}, ::Int64), :(Main.#myfun#6), 1.0, 1.0, 1.0e-5, 10.0, 0.0, 10.0, 0.0001, 1000000, 1, 1.0, :(#self#), :(x), :(v), :(distbin), :(mincount)))
  end::Any

If I specify the type of distbin (for example UnitRange{Int64}), then type inference also works again.
It seems to me that there is some internal limit for the function specialization and type inference.

Is this documented some where?
I see this behaviour on julia 0.6.2 and 0.6.1.

Julia Version 0.6.2
Commit d386e40c17 (2017-12-13 18:08 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i3-3120M CPU @ 2.50GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Sandybridge)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, ivybridge)

[yuyichao]

Dup of #22255