UnionAll inference issues

[jrevels]

Found in #41:

julia> using Cassette: @context, @prehook, @overdub

julia> @context Ctx

# This isn't prehook needed to reproduce, just gives us a little info about what's going on 
julia> @prehook (f::Any)(args...) where {__CONTEXT__<:Ctx} = println(f, args)

julia> bar(T) = isa(T, UnionAll) ? bar(T.body) : T
bar (generic function with 1 method)

julia> @overdub(Ctx(), bar(Vector{T} where T))
TypeVar(:T,)
Core.apply_type(Union,)
Core.apply_type(Array{T,1} where T, T)
UnionAll(T, Array{T,1})
bar(Array{T,1} where T,)
isa(Array{T,1} where T, UnionAll)
Base.getproperty(Array{T,1} where T, :body)
getfield(Array{T,1} where T, :body)
bar(Array{T,1},)
isa(Array{T,1}, UnionAll)
Array{T,1}

julia> bar(Vector{T} where T)
Array{T,1}

julia> @overdub(Ctx(), bar(Vector{Vector{T}} where T))
TypeVar(:T,)
Core.apply_type(Union,)
Core.apply_type(Array{T,1} where T, T)
Core.apply_type(Array{T,1} where T, Array{T,1})
UnionAll(T, Array{Array{T,1},1})
bar(Array{Array{T,1},1} where T,)
isa(Array{Array{T,1},1} where T, UnionAll)
Base.getproperty(Array{Array{T,1},1} where T, :body)
getfield(Array{Array{T,1},1} where T, :body)
bar(Array{Array{T,1},1},)
isa(Array{Array{T,1},1}, UnionAll)
Base.getproperty(Array{Array{T,1},1}, :body)
getfield(Array{Array{T,1},1}, :body)
ERROR: type DataType has no field body
Stacktrace:
 [1] overdub_execute at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:9 [inlined]
 [2] overdub_recurse at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:155 [inlined]
 [3] overdub_execute at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:34 [inlined]
 [4] overdub_recurse(::Ctx{Cassette.Unused,0x0000000000006ba7,Cassette.Unused,getfield(Main, Symbol("##CtxTag#1559")){Nothing,0x5e60b7525025d2c1}}, ::typeof(bar), ::Type{Array{Array{T,1},1} where T}) at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:155
 [5] overdub_execute at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:34 [inlined]
 [6] overdub_recurse(::Ctx{Cassette.Unused,0x0000000000006ba7,Cassette.Unused,getfield(Main, Symbol("##CtxTag#1559")){Nothing,0x5e60b7525025d2c1}}, ::typeof(bar), ::Type{Array{Array{T,1},1} where T}) at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:155
 [7] overdub_execute at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:34 [inlined]
 [8] overdub_recurse(::Ctx{Cassette.Unused,0x0000000000006ba7,Cassette.Unused,getfield(Main, Symbol("##CtxTag#1559")){Nothing,0x5e60b7525025d2c1}}, ::getfield(Main, Symbol("##16#17")), ::Ctx{Cassette.Unused,0x0000000000006ba7,Cassette.Unused,getfield(Main, Symbol("##CtxTag#1559")){Nothing,0x5e60b7525025d2c1}}) at /Users/jarrettrevels/.julia/v0.7/Cassette/src/overdub.jl:155
 [9] top-level scope at /Users/jarrettrevels/.julia/v0.7/Cassette/src/macros.jl:68

julia> bar(Vector{Vector{T}} where T)
Array{Array{T,1},1}

[jrevels]

ref JuliaLang/julia#27078

[jrevels]

closed upstream via JuliaLang/julia#27736