type_unstable.jl

julia> function dg()::Int
       N = 200000
       nheads::Int = @distributed (+) for i = 1:N
           Int(rand(Bool))
       end
       return nheads
       end
dg (generic function with 1 method)

julia> @code_warntype dg()
Body::Int64
1 ─ %1 = %new(Main.:(##42#43))::Core.Compiler.Const(getfield(Main, Symbol("##42#43"))(), false)
│   %2 = invoke Distributed.preduce(Main.:+::Function, %1::Function, $(QuoteNode(1:200000))::UnitRange{Int64})::Any
│   %3 = (Base.convert)(Main.Int, %2)::Any
│        (Core.typeassert)(%3, Main.Int)
│   %5 = π (%3, Int64)
└──      return %5