collect(Take(1), 1:1) cannot be inferred

[tkf]

It seems that the type instability happens in the anonymous function defined as the do bolck in next(rf::R_{Take}, result, input):

https://github.com/tkf/Transducers.jl/blob/eab67ddb94e0e6c82c0b65c41b1e218287d8675a/src/library.jl#L378-L388

The compiler gives up to track the union and decides to use Tuple{Int64, Union{Array, Reduced}} instead of Tuple{Int64, Union{Array{Union{},1}, Array{Int64,1}, Reduced{Array{Union{},1}}, Reduced{Array{Int64,1}}}}.

This probably is impossible to directly solve, since Julia compiler has the limit const MAX_TYPEUNION_LENGTH = 3 (but re-compiling Julia with length=4 didn't improve the inference result...)

Full `@​descend` session

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  | | |_| | | | (_| |  |  Version 1.3.0-DEV.533 (2019-07-10)
 _/ |\__'_|_|_|\__'_|  |  Commit 073cbbb491 (7 days old master)
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julia> using Transducers

julia> using Cthulhu

julia> @descend_code_warntype collect(Take(1), 1:1)

│ ─ %-1  = invoke collect(::Take,::UnitRange{Int64})::Any
Body::Any
     @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:599 within `collect'
1 ──        goto #2
     @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:603 within `collect'
    ┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:90 within `reducingfunction'
    │┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:90 within `#reducingfunction#60'
    ││┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:94 within `_reducingfunction'
    │││┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:94 within `#_reducingfunction#61'
    ││││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:338 within `Reduction' @ /home/takafumi/.julia/dev/Transducers/src/core.jl:336 @ /home/takafumi/.julia/dev/Transducers/src/core.jl:308
2 ──│││││ %2   = %new(Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE}, xf, $(QuoteNode(Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}}(Completing{typeof(BangBang.push!!)}(BangBang.push!!)))))::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE}
│   └└└└└
│    @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:604 within `collect'
│   ┌ @ array.jl:365 within `getindex'
│   │┌ @ boot.jl:423 within `Array' @ boot.jl:404
│   ││ %3   = $(Expr(:foreigncall, :(:jl_alloc_array_1d), Array{Union{},1}, svec(Any, Int64), :(:ccall), 2, Array{Union{},1}, 0, 0))::Array{Union{},1}
│   └└
│    @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:606 within `collect'
│   ┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:325 within `transduce'
│   │┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:326 within `#transduce#63'
│   ││┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:316 within `_start_init'
│   │││┌ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:375 within `start'
│   ││││┌ @ Base.jl:20 within `getproperty'
│   │││││ %4   = Base.getfield(xf, :n)::Int64
│   ││││└
│   ││││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:583 within `wrap'
│   │││││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:475 within `privatestate' @ /home/takafumi/.julia/dev/Transducers/src/core.jl:488
│   ││││││ %5   = %new(Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,Array{Union{},1}}, %4, %3)::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,Array{Union{},1}}
│   ││└└└└
│   ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:327 within `#transduce#63'
│   ││┌ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:154 within `__foldl__'
│   │││┌ @ range.jl:477 within `isempty'
│   ││││┌ @ range.jl:565 within `first'
│   │││││┌ @ Base.jl:20 within `getproperty'
│   ││││││ %6   = Base.getfield(coll, :start)::Int64
│   ││││└└
│   ││││┌ @ range.jl:570 within `last'
│   │││││┌ @ Base.jl:20 within `getproperty'
│   ││││││ %7   = Base.getfield(coll, :stop)::Int64
│   ││││└└
│   ││││┌ @ operators.jl:294 within `>'
│   │││││┌ @ int.jl:49 within `<'
│   ││││││ %8   = Base.slt_int(%7, %6)::Bool
│   │││└└└
└───│││        goto #4 if not %8
3 ──│││        goto #38
    │││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:155 within `__foldl__'
    │││┌ @ abstractarray.jl:212 within `eachindex'
    ││││┌ @ abstractarray.jl:95 within `axes1'
    │││││┌ @ abstractarray.jl:75 within `axes'
    ││││││┌ @ range.jl:473 within `size'
    │││││││┌ @ range.jl:543 within `length'
    ││││││││┌ @ range.jl:570 within `last'
    │││││││││┌ @ Base.jl:20 within `getproperty'
4 ──││││││││││ %11  = Base.getfield(coll, :stop)::Int64
│   ││││││││└└
│   ││││││││┌ @ range.jl:565 within `first'
│   │││││││││┌ @ Base.jl:20 within `getproperty'
│   ││││││││││ %12  = Base.getfield(coll, :start)::Int64
│   ││││││││└└
│   ││││││││┌ @ checked.jl:222 within `checked_sub'
│   │││││││││┌ @ checked.jl:194 within `sub_with_overflow'
│   ││││││││││ %13  = Base.Checked.checked_ssub_int(%11, %12)::Tuple{Int64,Bool}
│   │││││││││└
│   │││││││││┌ @ tuple.jl:63 within `indexed_iterate' @ tuple.jl:63
│   ││││││││││ %14  = Base.getfield(%13, 1)::Int64
│   ││││││││││ @ tuple.jl:63 within `indexed_iterate'
│   ││││││││││ %15  = Base.getfield(%13, 2)::Bool
│   │││││││││└
│   │││││││││ @ checked.jl:223 within `checked_sub'
└───│││││││││        goto #6 if not %15
5 ──│││││││││        invoke Base.Checked.throw_overflowerr_binaryop(:-::Symbol, %11::Int64, %12::Int64)
└───│││││││││        $(Expr(:unreachable))
    │││││││││ @ checked.jl:224 within `checked_sub'
6 ┄─│││││││││        goto #7
    ││││││││└
    ││││││││┌ @ checked.jl:165 within `checked_add'
    │││││││││┌ @ checked.jl:132 within `add_with_overflow'
7 ──││││││││││ %20  = Base.Checked.checked_sadd_int(%14, 1)::Tuple{Int64,Bool}
│   │││││││││└
│   │││││││││┌ @ tuple.jl:63 within `indexed_iterate' @ tuple.jl:63
│   ││││││││││ %21  = Base.getfield(%20, 1)::Int64
│   ││││││││││ @ tuple.jl:63 within `indexed_iterate'
│   ││││││││││ %22  = Base.getfield(%20, 2)::Bool
│   │││││││││└
│   │││││││││ @ checked.jl:166 within `checked_add'
└───│││││││││        goto #9 if not %22
8 ──│││││││││        invoke Base.Checked.throw_overflowerr_binaryop(:+::Symbol, %14::Int64, 1::Int64)
└───│││││││││        $(Expr(:unreachable))
    │││││││││ @ checked.jl:167 within `checked_add'
9 ┄─│││││││││        goto #10
    ││││││││└
10 ─││││││││        goto #11
    │││││││└
11 ─│││││││        goto #12
    ││││││└
    ││││││┌ @ tuple.jl:139 within `map'
    │││││││┌ @ range.jl:320 within `OneTo' @ range.jl:311
    ││││││││┌ @ promotion.jl:414 within `max'
    │││││││││┌ @ int.jl:49 within `<'
12 ─││││││││││ %29  = Base.slt_int(%21, 0)::Bool
│   │││││││││└
│   │││││││││ %30  = Base.ifelse(%29, 0, %21)::Int64
│   ││││││└└└
└───││││││        goto #13
    │││││└
13 ─│││││        goto #14
    ││││└
14 ─││││        goto #15
    │││└
    │││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:156 within `__foldl__'
    │││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:182 within `macro expansion'
    ││││┌ @ range.jl:625 within `getindex'
15 ─│││││        goto #16
    │││││ @ range.jl:626 within `getindex'
16 ─│││││        goto #17
    │││││ @ range.jl:618 within `getindex'
    │││││┌ @ Base.jl:20 within `getproperty'
17 ─││││││ %36  = Base.getfield(coll, :start)::Int64
│   │││││└
│   │││││┌ @ int.jl:52 within `-'
│   ││││││ %37  = Base.sub_int(1, 1)::Int64
│   │││││└
│   │││││┌ @ int.jl:53 within `+'
│   ││││││ %38  = Base.add_int(%36, %37)::Int64
│   │││││└
│   │││││ @ range.jl:619 within `getindex'
└───│││││        goto #18
    │││││ @ range.jl:620 within `getindex'
18 ─│││││        goto #19
    ││││└
19 ─││││ %41  = invoke Transducers.next(%2::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE}, %5::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,Array{Union{},1}}, %38::Int64)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
│   ││││ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:183 within `macro expansion'
│   ││││ %42  = (%41 isa Transducers.Reduced)::Bool
└───││││        goto #21 if not %42
20 ─││││ %44  = π (%41, Reduced)
└───││││        goto #38
    ││││ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:184 within `macro expansion'
21 ─││││ %46  = π (%41, Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A)
│   │││└
│   │││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:157 within `__foldl__'
│   │││┌ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:98 within `macro expansion'
└───││││        goto #22
    ││││ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:106 within `macro expansion'
    ││││┌ @ abstractarray.jl:303 within `lastindex'
    │││││┌ @ abstractarray.jl:268 within `eachindex'
    ││││││┌ @ abstractarray.jl:95 within `axes1'
    │││││││┌ @ abstractarray.jl:75 within `axes'
    ││││││││┌ @ tuple.jl:139 within `map'
    │││││││││┌ @ range.jl:320 within `OneTo' @ range.jl:311
    ││││││││││┌ @ promotion.jl:414 within `max'
    │││││││││││┌ @ int.jl:49 within `<'
22 ─││││││││││││ %48  = Base.slt_int(%30, 0)::Bool
│   │││││││││││└
│   │││││││││││ %49  = Base.ifelse(%48, 0, %30)::Int64
│   ││││└└└└└└└
│   ││││┌ @ range.jl:5 within `Colon'
│   │││││┌ @ range.jl:277 within `UnitRange'
│   ││││││┌ @ range.jl:282 within `unitrange_last'
│   │││││││┌ @ operators.jl:341 within `>='
│   ││││││││┌ @ int.jl:424 within `<='
│   │││││││││ %50  = Base.sle_int(2, %49)::Bool
│   │││││││└└
│   │││││││ %51  = Base.ifelse(%50, %49, 1)::Int64
│   ││││└└└
│   ││││┌ @ range.jl:593 within `iterate'
│   │││││┌ @ range.jl:477 within `isempty'
│   ││││││┌ @ operators.jl:294 within `>'
│   │││││││┌ @ int.jl:49 within `<'
│   ││││││││ %52  = Base.slt_int(%51, 2)::Bool
│   │││││└└└
└───│││││        goto #24 if not %52
23 ─│││││        goto #25
24 ─│││││        goto #25
    ││││└
25 ┄││││ %56  = φ (#23 => true, #24 => false)::Bool
│   ││││ %57  = φ (#24 => 2)::Int64
│   ││││ %58  = φ (#24 => 2)::Int64
│   ││││ %59  = Base.not_int(%56)::Bool
└───││││        goto #37 if not %59
26 ┄││││ %61  = φ (#25 => %46, #36 => %76)::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A
│   ││││ %62  = φ (#25 => %57, #36 => %82)::Int64
│   ││││ %63  = φ (#25 => %58, #36 => %83)::Int64
│   ││││ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:106 within `macro expansion' @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:158
│   ││││┌ @ range.jl:625 within `getindex'
└───│││││        goto #27
    │││││ @ range.jl:626 within `getindex'
27 ─│││││        goto #28
    ││││└
    ││││ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:106 within `macro expansion' @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:159 @ /home/takafumi/.julia/dev/Transducers/src/core.jl:182
    ││││┌ @ range.jl:618 within `getindex'
    │││││┌ @ Base.jl:20 within `getproperty'
28 ─││││││ %66  = Base.getfield(coll, :start)::Int64
│   │││││└
│   │││││┌ @ int.jl:52 within `-'
│   ││││││ %67  = Base.sub_int(%62, 1)::Int64
│   │││││└
│   │││││┌ @ int.jl:53 within `+'
│   ││││││ %68  = Base.add_int(%66, %67)::Int64
│   │││││└
│   │││││ @ range.jl:619 within `getindex'
└───│││││        goto #29
    │││││ @ range.jl:620 within `getindex'
29 ─│││││        goto #30
    ││││└
30 ─││││ %71  = Transducers.next(%2, %61, %68)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
│   ││││ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:106 within `macro expansion' @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:159 @ /home/takafumi/.julia/dev/Transducers/src/core.jl:183
│   ││││ %72  = (%71 isa Transducers.Reduced)::Bool
└───││││        goto #32 if not %72
31 ─││││ %74  = π (%71, Reduced)
└───││││        goto #38
    ││││ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:106 within `macro expansion' @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:159 @ /home/takafumi/.julia/dev/Transducers/src/core.jl:184
32 ─││││ %76  = π (%71, Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A)
│   ││││ @ /home/takafumi/.julia/dev/Transducers/src/simd.jl:106 within `macro expansion'
│   ││││┌ @ range.jl:597 within `iterate'
│   │││││┌ @ promotion.jl:403 within `=='
│   ││││││ %77  = (%63 === %51)::Bool
│   │││││└
└───│││││        goto #34 if not %77
33 ─│││││        goto #35
    │││││ @ range.jl:598 within `iterate'
    │││││┌ @ int.jl:53 within `+'
34 ─││││││ %80  = Base.add_int(%63, 1)::Int64
│   │││││└
│   │││││ @ range.jl:599 within `iterate'
└───│││││        goto #35
    ││││└
35 ┄││││ %82  = φ (#34 => %80)::Int64
│   ││││ %83  = φ (#34 => %80)::Int64
│   ││││ %84  = φ (#33 => true, #34 => false)::Bool
│   ││││ %85  = Base.not_int(%84)::Bool
└───││││        goto #37 if not %85
36 ─││││        goto #26
    │││└
    │││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:161 within `__foldl__'
37 ┄│││ %88  = φ (#35 => %76, #25 => %46)::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A
│   │││┌ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:376 within `complete'
│   ││││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:521 within `unwrap'
│   │││││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:497 within `psresult'
│   ││││││┌ @ Base.jl:20 within `getproperty'
│   │││││││ %89  = Base.getfield(%88, :result)::Any
│   │││└└└└
└───│││        goto #38
    ││└
38 ┄││ %91  = φ (#3 => %3, #20 => %44, #31 => %74, #37 => %89)::Any
│   ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:328 within `#transduce#63'
│   ││ %92  = Transducers.unreduced(%91)::Any
│   ││ %93  = (%92 isa Transducers.DefaultInit)::Bool
└───││        goto #40 if not %93
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:329 within `#transduce#63'
    ││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:1008 within `EmptyResultError'
39 ─│││ %95  = Transducers.EmptyResultError::Type{Transducers.EmptyResultError}
│   │││ %96  = %new(%95, %2)::Transducers.EmptyResultError
│   ││└
│   ││        Transducers.throw(%96)
└───││        $(Expr(:unreachable))
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:341 within `#transduce#63'
40 ┄││ %99  = Transducers.unreduced(%91)::Any
│   ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:342 within `#transduce#63'
│   ││ %100 = (%99 isa Transducers.InferableInit)::Bool
└───││        goto #44 if not %100
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:346 within `#transduce#63'
41 ─││ %102 = Transducers._nonidtype(Any)::Type{Any}
│   ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:351 within `#transduce#63'
│   ││ %103 = π (%99, Union{Transducers.DefaultInit{OP}, Transducers.OptInitOf{OP}} where OP)
│   ││ %104 = invoke Transducers.convert(%102::Type{Any}, %103::Any)::Union{Transducers.DefaultInit{OP}, Transducers.OptInitOf{OP}} where OP
│   ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:352 within `#transduce#63'
│   ││ %105 = (%91 isa Transducers.Reduced)::Bool
└───││        goto #43 if not %105
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:353 within `#transduce#63'
42 ─││ %107 = Transducers.Reduced(%104)::Reduced{_A} where _A
└───││        goto #47
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:355 within `#transduce#63'
43 ─││        goto #47
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:359 within `#transduce#63'
44 ─││ %110 = (%91 isa Transducers.Reduced)::Bool
└───││        goto #46 if not %110
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:360 within `#transduce#63'
45 ─││ %112 = Transducers.Reduced(%99)::Reduced{_A} where _A
└───││        goto #47
    ││ @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:362 within `#transduce#63'
46 ─││        goto #47
    │└
47 ┄│ %115 = φ (#42 => %107, #43 => %104, #45 => %112, #46 => %99)::Any
└───│        goto #48
    └
48 ─ %117 = Transducers.unreduced(%115)::Any
│    @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:607 within `collect'
│    %118 = (%117 isa Array{Union{},1})::Bool
└───        goto #53 if not %118
     @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:608 within `collect'
    ┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:944 within `macro expansion' @ array.jl:591
49 ─│        goto #50
50 ─│ %121 = π (false, Core.Compiler.Const(false, false))
└───│        goto #52 if not %121
51 ─│        nothing
    └
     @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:609 within `collect'
    ┌ @ array.jl:377 within `getindex'
    │┌ @ boot.jl:423 within `Array' @ boot.jl:404
52 ┄││ %124 = $(Expr(:foreigncall, :(:jl_alloc_array_1d), Array{Any,1}, svec(Any, Int64), :(:ccall), 2, Array{Any,1}, 0, 0))::Array{Any,1}
│   └└
└───        return %124
     @ /home/takafumi/.julia/dev/Transducers/src/processes.jl:611 within `collect'
53 ─        return %117

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   %17  = invoke throw_overflowerr_binaryop(::Symbol,::Int64,::Int64)::Union{}
   %24  = invoke throw_overflowerr_binaryop(::Symbol,::Int64,::Int64)::Union{}
 • %41  = invoke next(::Transducers.Reduction{…},::Transducers.PrivateState{…},::Int64{…})
   %71  = invoke next(::Transducers.Reduction{…},::Transducers.PrivateState{…},::Int64{…})
   %92  = call #unreduced(::Any)::Any
   %99  = call #unreduced(::Any)::Any
   %102  = invoke _nonidtype(::Type{Any})::Type{Any}
   %104  = invoke convert(::Type{Any},::Any)
   %107  = invoke Reduced(::Union{Transducers.DefaultInit{OP}, Transducers.OptInitOf{OP}} where OP)
v  %112  = invoke Reduced(::Any)::Reduced{_A} where _A

│ ─ %-1  = invoke next(::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,Array{Union{},1}},::Int64)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
Body::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
     @ /home/takafumi/.julia/dev/Transducers/src/library.jl:378 within `next'
    ┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:604 within `wrapping'
    │┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:521 within `unwrap'
    ││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:496 within `psstate'
    │││┌ @ Base.jl:20 within `getproperty'
1 ──││││ %1  = Base.getfield(result, :state)::Int64
│   ││└└
│   ││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:497 within `psresult'
│   │││┌ @ Base.jl:20 within `getproperty'
│   ││││ %2  = Base.getfield(result, :result)::Array{Union{},1}
│   │└└└
│   │ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:605 within `wrapping'
│   │┌ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:380 within `#7'
│   ││┌ @ operators.jl:294 within `>'
│   │││┌ @ int.jl:49 within `<'
│   ││││ %3  = Base.slt_int(0, %1)::Bool
│   ││└└
└───││       goto #3 if not %3
    ││ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:381 within `#7'
    ││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:285 within `next' @ /home/takafumi/.julia/dev/Transducers/src/core.jl:680 @ /home/takafumi/.julia/dev/Transducers/src/core.jl:422
    │││┌ @ /home/takafumi/.julia/dev/BangBang/src/base.jl:29 within `push!!'
    ││││┌ @ /home/takafumi/.julia/dev/BangBang/src/core.jl:5 within `may'
    │││││┌ @ /home/takafumi/.julia/dev/BangBang/src/NoBang/base.jl:10 within `push'
    ││││││┌ @ /home/takafumi/.julia/dev/BangBang/src/NoBang/singletoncontainers.jl:5 within `SingletonVector' @ /home/takafumi/.julia/dev/BangBang/src/NoBang/singletoncontainers.jl:5
2 ──│││││││ %5  = %new(BangBang.NoBang.SingletonVector{Int64}, input)::BangBang.NoBang.SingletonVector{Int64}
│   ││││││└
│   ││││││┌ @ abstractarray.jl:1287 within `vcat'
│   │││││││ %6  = Core.tuple(%2, %5)::Tuple{Array{Union{},1},BangBang.NoBang.SingletonVector{Int64}}
│   │││││││┌ @ abstractarray.jl:1373 within `typed_vcat'
│   ││││││││ %7  = invoke Base._typed_vcat(Int64::Type{Int64}, %6::Tuple{Array{Union{},1},BangBang.NoBang.SingletonVector{Int64}})::Array{Int64,1}
│   ││└└└└└└
│   ││ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:382 within `#7'
│   ││┌ @ int.jl:52 within `-'
└───│││ %8  = Base.sub_int(%1, 1)::Int64
    ││└
    ││ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:384 within `#7'
3 ┄─││ %9  = φ (#2 => %8, #1 => %1)::Int64
│   ││ %10 = φ (#2 => %7, #1 => %2)::Union{Array{Int64,1}, Array{Union{},1}}
│   ││┌ @ int.jl:424 within `<='
│   │││ %11 = Base.sle_int(%9, 0)::Bool
│   ││└
└───││       goto #15 if not %11
    ││ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:385 within `#7'
4 ──││ %13 = π (%10, Union{Array{Union{},1}, Array{Int64,1}})
│   ││ %14 = (isa)(%13, Array{Union{},1})::Bool
└───││       goto #6 if not %14
5 ──││ %16 = π (%13, Array{Union{},1})
└───││       goto #9
6 ──││ %18 = (isa)(%13, Array{Int64,1})::Bool
└───││       goto #8 if not %18
7 ──││ %20 = π (%13, Array{Int64,1})
└───││       goto #9
8 ──││       Core.throw(ErrorException("fatal error in type inference (type bound)"))
└───││       $(Expr(:unreachable))
9 ┄─││ %24 = φ (#5 => %16, #7 => %20)::Union{Array{Union{},1}, Array{Int64,1}}
│   ││ %25 = (isa)(%24, Array{Union{},1})::Bool
└───││       goto #11 if not %25
10 ─││ %27 = π (%24, Array{Union{},1})
│   ││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:93 within `reduced'
│   │││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:49 within `Reduced' @ /home/takafumi/.julia/dev/Transducers/src/core.jl:49
│   ││││ %28 = %new(Reduced{Array{Union{},1}}, %27)::Reduced{Array{Union{},1}}
│   ││└└
└───││       goto #14
11 ─││ %30 = (isa)(%24, Array{Int64,1})::Bool
└───││       goto #13 if not %30
12 ─││ %32 = π (%24, Array{Int64,1})
│   ││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:93 within `reduced'
│   │││┌ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:49 within `Reduced' @ /home/takafumi/.julia/dev/Transducers/src/core.jl:49
│   ││││ %33 = %new(Reduced{Array{Int64,1}}, %32)::Reduced{Array{Int64,1}}
│   ││└└
└───││       goto #14
13 ─││       Core.throw(ErrorException("fatal error in type inference (type bound)"))
└───││       $(Expr(:unreachable))
14 ┄││ %37 = φ (#10 => %28, #12 => %33)::Union{Reduced{Array{Union{},1}}, Reduced{Array{Int64,1}}}
    ││ @ /home/takafumi/.julia/dev/Transducers/src/library.jl:387 within `#7'
15 ┄││ %38 = φ (#14 => %37, #3 => %10)::Union{Array, Reduced}
└───││       goto #16
    │└
    │ @ /home/takafumi/.julia/dev/Transducers/src/core.jl:606 within `wrapping'
16 ─│ %40 = Transducers.wrap(rf, %9, %38)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
└───│       goto #17
    └
17 ─       return %40

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 • %7  = invoke _typed_vcat(::Type{Int64},::Tuple{Array{Union{},1},BangBang.NoBang.SingletonVector{Int64}})
   %40  = call #wrap(::Transducers.Reduction{…},::Int64{…},::Union{Array, Reduced}{…})
   ↩

Here I type o.

│ ─ %-1  = invoke next(::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,Array{Union{},1}},::Int64)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
Body::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
    @ /home/takafumi/.julia/dev/Transducers/src/library.jl:378 within `next'
1 ─ %1 = Transducers.:(##7#8)::Core.Compiler.Const(getfield(Transducers, Symbol("##7#8")), false)
│   %2 = Core.typeof(rf)::Core.Compiler.Const(Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE}, false)
│   %3 = Core.typeof(input)::Core.Compiler.Const(Int64, false)
│   %4 = Core.apply_type(%1, %2, %3)::Core.Compiler.Const(getfield(Transducers, Symbol("##7#8")){Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64}, false)
│        (#7 = %new(%4, rf, input))
│   %6 = #7::getfield(Transducers, Symbol("##7#8")){Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64}
│   %7 = Transducers.wrapping(%6, rf, result)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
└──      return %7

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 • %7  = invoke wrapping(…,…,…)
   ↩

│ ─ %-1  = invoke wrapping(::getfield(Transducers, Symbol("##7#8")){Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64},::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},::Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,Array{Union{},1}})::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
Body::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
1 ─       nothing
│   @ /home/takafumi/.julia/dev/Transducers/src/core.jl:604 within `wrapping'
│   %2  = Transducers.unwrap(rf, result)::Tuple{Int64,Array{Union{},1}}
│   %3  = Base.indexed_iterate(%2, 1)::Core.Compiler.PartialStruct(Tuple{Int64,Int64}, Any[Int64, Core.Compiler.Const(2, false)])
│         (state0 = Core.getfield(%3, 1))
│         (@_6 = Core.getfield(%3, 2))
│   %6  = Base.indexed_iterate(%2, 2, @_6::Core.Compiler.Const(2, false))::Core.Compiler.PartialStruct(Tuple{Array{Union{},1},Int64}, Any[Array{Union{},1}, Core.Compiler.Const(3, false)])
│         (iresult0 = Core.getfield(%6, 1))
│   @ /home/takafumi/.julia/dev/Transducers/src/core.jl:605 within `wrapping'
│   %8  = (f)(state0, iresult0)::Tuple{Int64,Union{Array, Reduced}}
│   %9  = Base.indexed_iterate(%8, 1)::Core.Compiler.PartialStruct(Tuple{Int64,Int64}, Any[Int64, Core.Compiler.Const(2, false)])
│         (state1 = Core.getfield(%9, 1))
│         (@_9 = Core.getfield(%9, 2))
│   %12 = Base.indexed_iterate(%8, 2, @_9::Core.Compiler.Const(2, false))::Core.Compiler.PartialStruct(Tuple{Union{Array, Reduced},Int64}, Any[Union{Array, Reduced}, Core.Compiler.Const(3, false)])
│         (iresult1 = Core.getfield(%12, 1))
│   @ /home/takafumi/.julia/dev/Transducers/src/core.jl:606 within `wrapping'
│   %14 = Transducers.wrap(rf, state1, iresult1)::Union{Transducers.PrivateState{Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE},Int64,_A} where _A, Reduced}
└──       return %14

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   %2  = invoke unwrap(::Transducers.Reduction{…},::Transducers.PrivateState{…})::Tuple{Int64,Array{Union{},1}}
   %3  = invoke indexed_iterate(::Tuple{Int64,Array{Union{},1}},::Int64)
   %6  = invoke indexed_iterate(::Tuple{Int64,Array{Union{},1}},::Int64,::Int64)
 • %8  = invoke #7(::Int64,::Array{Union{},1})::Tuple{Int64,Union{Array, Reduced}}
   %9  = invoke indexed_iterate(::Tuple{Int64,Union{Array, Reduced}},::Int64)
   %12  = invoke indexed_iterate(::Tuple{Int64,Union{Array, Reduced}},::Int64,::Int64)
   %14  = call #wrap(::Transducers.Reduction{…},::Int64{…},::Union{Array, Reduced}{…})
   ↩

│ ─ %-1  = invoke #7(::Int64,::Array{Union{},1})::Tuple{Int64,Union{Array, Reduced}}
Body::Tuple{Int64,Union{Array, Reduced}}
    @ /home/takafumi/.julia/dev/Transducers/src/library.jl:380 within `#7'
1 ─       (iresult@_5 = iresult@_3)
│         (n@_4 = n@_2)
│   %3  = (n@_4 > 0)::Bool
└──       goto #3 if not %3
    @ /home/takafumi/.julia/dev/Transducers/src/library.jl:381 within `#7'
2 ─ %5  = Core.getfield(#self#, :rf)::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE}
│   %6  = Transducers.inner(%5)::Core.Compiler.Const(Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}}(Completing{typeof(BangBang.push!!)}(BangBang.push!!)), false)
│   %7  = iresult@_5::Array{Union{},1}::Array{Union{},1}
│   %8  = Core.getfield(#self#, :input)::Int64
│         (iresult@_5 = Transducers.next(%6, %7, %8))
│   @ /home/takafumi/.julia/dev/Transducers/src/library.jl:382 within `#7'
└──       (n@_4 = n@_4 - 1)
    @ /home/takafumi/.julia/dev/Transducers/src/library.jl:384 within `#7'
3 ┄ %11 = (n@_4 <= 0)::Bool
└──       goto #5 if not %11
    @ /home/takafumi/.julia/dev/Transducers/src/library.jl:385 within `#7'
4 ─ %13 = Core.getfield(#self#, :rf)::Transducers.Reduction{Take,Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}},Transducers.NOTYPE}
│   %14 = Transducers.inner(%13)::Core.Compiler.Const(Transducers.BottomRF{Transducers.NOTYPE,Completing{typeof(BangBang.push!!)}}(Completing{typeof(BangBang.push!!)}(BangBang.push!!)), false)
│   %15 = Transducers.complete(%14, iresult@_5::Union{Array{Union{},1}, Array{Int64,1}})::Union{Array{Union{},1}, Array{Int64,1}}
└──       (iresult@_5 = Transducers.reduced(%15))
    @ /home/takafumi/.julia/dev/Transducers/src/library.jl:387 within `#7'
5 ┄ %17 = Core.tuple(n@_4, iresult@_5)::Tuple{Int64,Union{Array, Reduced}}
└──       return %17

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 • %3  = invoke >(::Int64,::Int64)::Bool
   %6  = invoke inner(::Transducers.Reduction{…})
   %9  = invoke next(::Transducers.BottomRF{…},::Array{…},::Int64{…})::Array{Int64,1}
   %10  = invoke -(::Int64,::Int64)::Int64
   %11  = invoke <=(::Int64,::Int64)::Bool
   %14  = invoke inner(::Transducers.Reduction{…})
   %15  = invoke complete(::Transducers.BottomRF{…},::Union{Array{Union{},1}, Array{Int64,1}}{…})
   %16  = invoke reduced(::Union{Array{Union{},1}, Array{Int64,1}})
   ↩