add syntax for empty n-dimensional arrays

[simeonschaub]

Might be worth backporting to 1.7 for consistency? Otherwise, this should probably have a NEWS entry.

closes #41389
cc: @BioTurboNick

[BioTurboNick]

Nice, you didn't even have to touch julia-syntax.scm to make it work.

Currently the parser allows this:

[;;
;]
0×0×0 Array{Any, 3}

Line breaks between semicolons produce an error normally:

[1 ;;
;]
ERROR: syntax: semicolons may appear before or after a line break in an array expression, but not both
Stacktrace:
 [1] top-level scope
   @ none:1

[simeonschaub]

Currently the parser allows this:

[;;
;]
0×0×0 Array{Any, 3}

Oh, weird, I thought the disallow-space would catch this.

[StefanKarpinski]

I'm not sure that leading/trailing spaces should be an error...

[simeonschaub]

Yeah, I think I agree. Will change it.

[vtjnash]

bump?

[simeonschaub]

Probably better to not backport this PR at this point.

[PallHaraldsson]

Why probably not better to backport? If 1.7 ends up as LTS, then it's very useful to have all new syntax in. [I believe syntax can't be added with Compat.jl.]

[simeonschaub]

1.7 won't become the LTS. The same argument could be made for any feature. 1.7 is already taking longer to finalize than usual, so I don't think we should stretch that out any further by backporting additional feature.

[simeonschaub]

This should be ready, @JeffBezanson do you want to give this a review?