`ERROR: TypeVar in Vararg length must have bounds Union{} and Any` in `Test.detect_ambiguities(ArrayInterface)`

[chriselrod]

E.g.:

julia> using ArrayInterface, Test

julia> Test.detect_ambiguities(ArrayInterface)
ERROR: TypeVar in Vararg length must have bounds Union{} and Any
Stacktrace:
 [1] _methods_by_ftype
   @ ./reflection.jl:884 [inlined]
 [2] (::Test.var"#examine#37"{Bool, Bool, Vector{Module}, Test.var"#sortdefs#36", Set{Tuple{Method, Method}}})(mt::Core.MethodTable)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1481
 [3] detect_ambiguities(mods::Module; recursive::Bool, ambiguous_bottom::Bool)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1506
 [4] detect_ambiguities(mods::Module)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1468
 [5] top-level scope
   @ REPL[4]:1

julia> Test.detect_ambiguities(ArrayInterface, ambiguous_bottom=true)
ERROR: TypeVar in Vararg length must have bounds Union{} and Any
Stacktrace:
 [1] _methods_by_ftype
   @ ./reflection.jl:884 [inlined]
 [2] (::Test.var"#examine#37"{Bool, Bool, Vector{Module}, Test.var"#sortdefs#36", Set{Tuple{Method, Method}}})(mt::Core.MethodTable)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1481
 [3] detect_ambiguities(mods::Module; recursive::Bool, ambiguous_bottom::Bool)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1506
 [4] top-level scope
   @ REPL[10]:1

[JeffBezanson]

I have not been able to reproduce this. What version of ArrayInterface?

[chriselrod]

ArrayInterface master:

julia> using Test, ArrayInterface
[ Info: Precompiling ArrayInterface [4fba245c-0d91-5ea0-9b3e-6abc04ee57a9]

julia> Test.detect_ambiguities(ArrayInterface)
ERROR: TypeVar in Vararg length must have bounds Union{} and Any
Stacktrace:
 [1] _methods_by_ftype
   @ ./reflection.jl:884 [inlined]
 [2] (::Test.var"#examine#37"{Bool, Bool, Vector{Module}, Test.var"#sortdefs#36", Set{Tuple{Method, Method}}})(mt::Core.MethodTable)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1481
 [3] detect_ambiguities(mods::Module; recursive::Bool, ambiguous_bottom::Bool)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1506
 [4] detect_ambiguities(mods::Module)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1468
 [5] top-level scope
   @ REPL[3]:1

Also on the latest release:

julia> using ArrayInterface, Test

julia> Test.detect_ambiguities(ArrayInterface)
ERROR: TypeVar in Vararg length must have bounds Union{} and Any
Stacktrace:
 [1] _methods_by_ftype
   @ ./reflection.jl:884 [inlined]
 [2] (::Test.var"#examine#37"{Bool, Bool, Vector{Module}, Test.var"#sortdefs#36", Set{Tuple{Method, Method}}})(mt::Core.MethodTable)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1481
 [3] detect_ambiguities(mods::Module; recursive::Bool, ambiguous_bottom::Bool)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1506
 [4] detect_ambiguities(mods::Module)
   @ Test ~/Documents/languages/julia/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1468
 [5] top-level scope
   @ REPL[2]:1

(loopvecrelease) pkg> st ArrayInterface
      Status `~/Documents/progwork/julia/env/loopvecrelease/Project.toml`
  [4fba245c] ArrayInterface v3.1.1

You can see CI failures here.

This regression is very recent. I had to rebuild master to get it.
With that in mind, it should be easy to bisect.

[vtjnash]

It started failing PkgEval today: https://s3.amazonaws.com/julialang-reports/nanosoldier/pkgeval/by_date/2021-02/16/ArrayInterface.1.7.0-DEV-093b2a6ea9.log

[vtjnash]

julia> T = Tuple{Type{A}, Type{T}} where T<:(AbstractArray{I, N} where N) where I<:(Base.IteratorsMD.CartesianIndex{N} where N) where A
Tuple{Type{A}, Type{T}} where {A, I<:(CartesianIndex), T<:(AbstractArray{I, N} where N)}

julia> S = Tuple{Type{A}, Type{T}} where T<:(Base.IteratorsMD.CartesianIndices{N, R} where R<:Tuple{Vararg{Base.OrdinalRange{Int64, Int64}, N}} where N) where A
Tuple{Type{A}, Type{T}} where {A, T<:(CartesianIndices)}

julia> typeintersect(T, S)
ERROR: TypeVar in Vararg length must have bounds Union{} and Any
Stacktrace:
 [1] typeintersect(a::Any, b::Any)
   @ Base ./reflection.jl:626
 [2] top-level scope
   @ REPL[13]:1

julia> typeintersect(S, T)
Tuple{Type{A}, Type{T}} where {A, T<:(CartesianIndices{N, R} where R<:Tuple{Vararg{OrdinalRange{Int64, Int64}, N}})}

Which happens when it tries to allocate the following approximate expression:

julia> Tuple{Vararg{T,N}} where {T, M, M<:N<:Any}
ERROR: TypeVar in Vararg length must have bounds Union{} and Any
Stacktrace:
 [1] top-level scope
   @ REPL[18]:1

[JeffBezanson]

Ah it's super recent.

[JeffBezanson]

Probably #39623