allow Array{T,N}() for arbitrary N

[KristofferC]

Closes #14201

[stevengj]

This syntax seems a bit weird to me.

[KristofferC]

What syntax? Array{T, N}() ?

[martinholters]

I'd favor deprecating the N==1 and N==2 cases, but if we're going with this, I think we can safely remove those from boot.jl, no?

[KristofferC]

Unless they are used there? I was also worried if the splatting carried some performance problems but could just check the generated code. I don't think this should be deprecated, it is a convenient way to put a place holder object in a type that you will swap out later.

[martinholters]

Unless they are used there?

I think base only uses this for N==1 and only in files included after array.jl, so things should be good.

it is a convenient way to put a place holder object in a type that you will swap out later.

I guess you only need it if N is largish or unknown at code-writing-time, so that spelling out the 0s is impractical/impossible. Is that common? Should we consider different syntax, e.g. empty(Array{T,N})?

[KristofferC]

Removed the boot.jl definitions.

[stevengj]

I would rather deprecate the N=1 and N=2 cases than add this syntax; I didn't even realize we had those.

[mbauman]

See #11154 for a bit of history. I think that Vector() and Vector{Int}() are somewhat common first attempts at constructing a vector for new users… but at the same time, learning those signatures generalizes poorly. See the comment within that thread about Array{Any}()'s surprising behavior within that context and the immediate desire for Vector(1,2,3) => Any[1,2,3].

I'm rather ambivalent here, but I agree it should be all or none. It'd be interesting to see how common Vector{T}() is across registered packages.

[KristofferC]

Rekt by #20330

[StefanKarpinski]

Sorry, man!

[KristofferC]

I just wanted to close #14201 (which I just did) so end result is the same