pmap error with type-parametric closures

[EthanAnderes]

I've been using closures to handle a complicated distributed project and ran into an error that seems like it could be a bug.

Here is a simple example which gives an error on both v0.6 and v0.7. Note: the parametric type T is what is causing the problem.

addprocs(2)

function gen_f(a::T) where T 
    f = x -> T(x)
    return f
end
f = gen_f(1f0)

map(f,  [1, 2]) # <--- works fine
pmap(f, [1, 2]) # <--- deserialization error

As was noted on discourse ref there is a workaround but results in a performance hit.

function gen_g(a)
    T = typeof(a)
    g = x -> T(x)
    return g
end
g = gen_g(1f0)

map(g,  [1, 2]) # <--- works fine
pmap(g, [1, 2]) # <--- works fine

julia> using BenchmarkTools

julia> @benchmark map($f,  $([1, 2]))
BenchmarkTools.Trial: 
  memory estimate:  112 bytes
  allocs estimate:  2
  --------------
  minimum time:     490.784 ns (0.00% GC)
  median time:      554.794 ns (0.00% GC)
  mean time:        574.588 ns (1.89% GC)
  maximum time:     13.989 μs (92.32% GC)
  --------------
  samples:          10000
  evals/sample:     194

julia> @benchmark map($g,  $([1, 2]))
BenchmarkTools.Trial: 
  memory estimate:  176 bytes
  allocs estimate:  5
  --------------
  minimum time:     1.392 μs (0.00% GC)
  median time:      1.575 μs (0.00% GC)
  mean time:        1.583 μs (0.00% GC)
  maximum time:     7.873 μs (0.00% GC)
  --------------
  samples:          10000
  evals/sample:     10