Fix IndexStyle and abstract depwarns on 0.6

[timholy]

When someone tags this, it should probably be a minor version bump since it introduces a new deprecation.

[mauro3]

Is there no const needed?

[timholy]

It doesn't appear to be necessary (see Julia's NEWS.md file), but it doesn't seem to hurt either. Most but not all of them in https://github.com/JuliaLang/julia/pull/20500/files seem to use const, so I can add it if you prefer.

[mauro3]

That NEWS.md entry is a bit confusing. Anyway, it does seem to make a difference (unless something changed on 0.6 in the last 5 days):

julia> V = Int
Int64

julia> f() = convert(V,5.0)
f (generic function with 1 method)

julia> @code_warntype f()
Variables:
  #self#::#f

Body:
  begin
      return (Main.convert)(Main.V, 5.0)::Any
  end::Any

julia> const VV = Int
Int64

julia> ff() = convert(VV,5.0)
ff (generic function with 1 method)

julia> @code_warntype ff()
Variables:
  #self#::#ff

Body:
  begin
      return $(Expr(:invoke, MethodInstance for convert(::Type{Int64}, ::Float64), :(Main.convert), :(Main.VV), 5.0))
  end::Int64

So, probably better add the const.

[timholy]

Parametric types seem different:

julia> MyVector{T} = AbstractArray{T, 1}
AbstractArray{T,1} where T

julia> f(a) = convert(MyVector, a)
f (generic function with 1 method)

julia> @code_warntype f([1,2,3])
Variables:
  #self#::#f
  a::Array{Int64,1}

Body:
  begin 
      return a::Array{Int64,1}
  end::Array{Int64,1}

but nevertheless I'll add the const.

[tkelman]

the const is implicit for parametric type aliases, but IMO a useful signal about what the line is doing

[mauro3]

Thanks Tim!

[timholy]

OK to tag?

If you haven't set up your repos for attobot, it does make life easier.

[mauro3]

Here it is: JuliaLang/METADATA.jl#8049

(Sometimes I need more prodding than the gentle hint you made in your first post ;-)