defalg method ambiguity

[DrChainsaw]

It seems like there is a method ambiguity when InlineStrings is added.

One example where it popped up in the wild: JuliaParallel/Dagger.jl#315

julia> tuple() |> collect |> sort
Union{}[]

julia> sort([missing, missing])
2-element Vector{Missing}:
 missing
 missing

julia> using InlineStrings

julia> tuple() |> collect |> sort
ERROR: MethodError: defalg(::Vector{Union{}}) is ambiguous. Candidates:
  defalg(v::AbstractArray{<:Union{Missing, Number}}) in Base.Sort at sort.jl:658
  defalg(::AbstractArray{<:Union{Missing, String1, String15, String3, String7}}) in InlineStrings at \.julia\packages\InlineStrings\aWvyB\src\InlineStrings.jl:698
Possible fix, define
  defalg(::AbstractArray{<:Missing})

julia> sort([missing, missing])
ERROR: MethodError: defalg(::Vector{Missing}) is ambiguous. Candidates:
etc...

[bkamins]

This is a bug in Julia Base, but for the time being unfortunately it has to be resolved in InlineStrings.jl.

@quinnj I propose to define the following methods:

defalg(::AbstractArray{Union{Missing, String1}})
defalg(::AbstractArray{Union{Missing, String3}})
defalg(::AbstractArray{Union{Missing, String7}})
defalg(::AbstractArray{Union{Missing, String15}})
defalg(::AbstractArray{String1})
defalg(::AbstractArray{String3})
defalg(::AbstractArray{String7})
defalg(::AbstractArray{String15})

which should resolve the issue.

[bkamins]

JuliaLang/julia#43426

[epatters]

Just ran into this one myself. Hopefully a workaround can be merged soon.

[caseykneale]

Similar story here:

ERROR: LoadError: MethodError: defalg(::Vector{Union{}}) is ambiguous. Candidates:
  defalg(v::AbstractArray{var"#s832", N} where {var"#s832"<:Union{Missing, Number}, N}) in Base.Sort at sort.jl:653
  defalg(::AbstractArray{var"#s86", N} where {var"#s86"<:Union{Missing, InlineStrings.String1, InlineStrings.String15, InlineStrings.String3, InlineStrings.String7}, N}) in InlineStrings at /home/runner/.julia/packages/InlineStrings/F5Dhz/src/InlineStrings.jl:698
Possible fix, define
  defalg(::AbstractArray{var"#s86", N} where {var"#s86"<:Missing, N})

Looks like the patch to Base got merged, but likely won't be back-ported?

[quinnj]

This was backported to 1.7