inconsistent eachindex: first on a variable array causes a BoundsError when the indexing base is not one

[nsajko]

Minimal reproducer:

using Symbolics
@variables x[0:2]
first(x)  # errors

Seems to be caused by this inconsistency:

julia> using Symbolics

julia> @variables x[0:2]
1-element Vector{Symbolics.Arr{Num, 1}}:
 x[1:3]

julia> ci = eachindex(x)
CartesianIndices((0:2,))

julia> li = eachindex(IndexLinear(), x)
1:3

julia> first(ci)
CartesianIndex(0,)

julia> first(li)
1

Note that Base.first is currently implemented as first(a::AbstractArray) = a[first(eachindex(a))].

[shashi]

Ahh I thought that @variables x[0:2] should error. Indexes not starting from 1 are not really supported