spaces in comprehensions

[atbug]

On both 0.7.0-alpha and 0.6.3:

julia> [1 +1 for i in 1:2]
ERROR: syntax: invalid comprehension syntax

julia> [1+1 for i in 1:2]
2-element Array{Int64,1}:
 2
 2

julia> [1+ 1 for i in 1:2]
2-element Array{Int64,1}:
 2
 2

julia> [1 + 1 for i in 1:2]
2-element Array{Int64,1}:
 2
 2

I think the intention of [1 +1 for i in 1:2] is clearly 1+1, not [1, +1], unless there are some other confusing situations?

[tomaklutfu]

Though intention is that so, I think it is ambiguous with infix + methods.

[garrison]

Another one I've noticed:

julia> [1 +
        x for x in 1:4]
ERROR: syntax: invalid comprehension syntax

See also #9494

[JeffBezanson]

The issue here is hcat syntax, where [1 -2] makes a 1x2 array. So it thinks [1 +1 ...is an hcat, at which point it's too late for it to be a comprehension. The case with the newline,

[1 +
 x for ...

seems like it could maybe be made to work.

As a footnote, since it's come up in the past, note that

[1
 + x for ...

is never going to work. Since we don't require ; statement separators, we can't join expressions with operators on the next line.

[JeffBezanson]

The case with the line break was fixed by #20265. The other case I don't think can be fixed.