Closure on parametric isbits instance allocates a lot

[cstjean]

My code uses large parametric types, and I've found that making types more parametric can make everything 2X slower (excluding compilation time). Here's a 500X slowdown MWE:

# Julia Version 0.6.0-pre.beta.353
using BenchmarkTools

struct param{C}
    c::C
end

@noinline foo(x, flag) = x

function bar(x, flag)
    map() do
        rec() = foo(x, flag)
        rec()
    end
end
c = (1, (1, (((), (((1, (1, Val{:a}())), 1), 1)), 1)))

@btime bar(param(c), true)
> 5.523 μs (14 allocations: 800 bytes)
@btime bar(param{Any}(c), true);
> 9.136 ns (1 allocation: 16 bytes)

As far as I could tell, all of those parentheses are necessary.

[cstjean]

It seems that most of the allocations come from dispatching on non-const globals, and returning a large value to the REPL; sorry for the noise.