Crash when printing array

[nalimilan]

It's been noted at #26927 that the following code makes Julia crash. The convert method is needed to be able to create the array (else a MethodError is thrown).

julia> Base.convert(::Type{Union{Missing, Nothing, T}}, x::Any) where {T} = convert(T, x)

julia> x = [missing, nothing, Some(nothing), Some(missing)];

julia> x
4-element Array{Union{Missing, Nothing, Some{Union{Missing, Nothing}}},1}:
 missing      
 nothing      
 
signal (11): Segmentation fault
in expression starting at no file:0
CreateSub at /home/milan/Dev/julia/usr/include/llvm/IR/IRBuilder.h:800
[...]

[fisiognomico]

I replied the bugged code, by shuffling the array elements some other combinations still segfault, but others give a more more interesting error message

julia> x = [Some(nothing), Some(missing), nothing, missing];
ERROR: MethodError: promote_rule(::Type{Union{Missing, Some{Missing}, Nothing}}, ::Type{Some{Nothing}}) is ambiguous. Candidates:
  promote_rule(::Type{Union{Missing, S}}, ::Type{T}) where {T, S} in Base at missing.jl:29
  promote_rule(::Type{Union{Nothing, S}}, ::Type{T}) where {T, S} in Base at missing.jl:29
Possible fix, define
  promote_rule(::Type{Union{Missing, Nothing}}, ::Type{T})
Stacktrace:
 [1] promote_type(::Type{Some{Nothing}}, ::Type{Union{Missing, Some{Missing}, Nothing}}) at ./promotion.jl:220
 [2] promote_typeof(::Some{Nothing}, ::Some{Missing}, ::Vararg{Any,N} where N) at ./promotion.jl:263
 [3] vect(::Some{Nothing}, ::Vararg{Any,N} where N) at ./array.jl:103
 [4] top-level scope

julia> x
2-element Array{Some{Union{Missing, Nothing}},1}:
 nothing
 missing

julia> x = [missing, Some(nothing), Some(missing), nothing];
ERROR: MethodError: convert(::Type{Union{Missing, Nothing, Some{Union{Missing, Nothing}}}}, ::Some{Nothing}) is ambiguous. Candida
tes:
  convert(::Type{Union{Missing, T}}, x) where T in Base at missing.jl:39
  convert(::Type{Union{Nothing, T}}, x) where T in Base at some.jl:21
Possible fix, define
  convert(::Type{Union{Missing, Nothing}}, ::Any)
Stacktrace:
 [1] setindex!(::Array{Union{Missing, Nothing, Some{Union{Missing, Nothing}}},1}, ::Some{Nothing}, ::Int64) at ./array.jl:705
 [2] copyto!(::Array{Union{Missing, Nothing, Some{Union{Missing, Nothing}}},1}, ::Tuple{Missing,Some{Nothing},Some{Missing},Nothin
g}) at ./abstractarray.jl:622
 [3] vect(::Missing, ::Vararg{Any,N} where N) at ./array.jl:106
 [4] top-level scope

julia> x = [nothing, missing, Some(nothing), Some(missing)];
ERROR: MethodError: convert(::Type{Union{Missing, Nothing, Some{Union{Missing, Nothing}}}}, ::Some{Nothing}) is ambiguous. Candida
tes:
  convert(::Type{Union{Missing, T}}, x) where T in Base at missing.jl:39
  convert(::Type{Union{Nothing, T}}, x) where T in Base at some.jl:21
Possible fix, define
  convert(::Type{Union{Missing, Nothing}}, ::Any)
Stacktrace:
 [1] setindex!(::Array{Union{Missing, Nothing, Some{Union{Missing, Nothing}}},1}, ::Some{Nothing}, ::Int64) at ./array.jl:705
 [2] copyto!(::Array{Union{Missing, Nothing, Some{Union{Missing, Nothing}}},1}, ::Tuple{Nothing,Missing,Some{Nothing},Some{Missing
}}) at ./abstractarray.jl:622
 [3] vect(::Nothing, ::Vararg{Any,N} where N) at ./array.jl:106
 [4] top-level scope

[JeffBezanson]

I can't reproduce the crash.

[nalimilan]

Cool, looks like it's been fixed recently (since May 5) on master.