Allow interpolation in using and export statement

[yuyichao]

This should be useful for some packages (especially for export). Using is probably less useful but why not....

Fix #11332

[yuyichao]

Note that the test for using need to construct the whole AST manually because of #10910 .

[ihnorton]

cc @jakebolewski

[JeffBezanson]

Looks fine. Just needs a rebase now.

[yuyichao]

Done.

[JeffBezanson]

I think I'm going to have to revert this. It breaks parsing of imports like

import Base: &
x

where it now tries to parse & as a unary operator and so grabs the x on the next line.

[yuyichao]

I see. I'll try to fix it and submit a new one.

[yuyichao]

@JeffBezanson

I think this issue is not specific to export and import/using. parse-unary-prefix seems to parse pass newline.

julia> &
& (generic function with 35 methods)

julia> parse("a = &\nb")
:(a = &b)

julia> parse("a = &")
:(a = (&))

julia> a = &
& (generic function with 35 methods)

julia> a
& (generic function with 35 methods)

Is this intentional and I should special case export/import or I should fix parse-unary-prefix?

P.S. I thought you've already reverted it so I was taking my time before getting back to this.....

[yuyichao]

@JeffBezanson

And the export/import is just a special case for it.

julia> parse("export &")
:(export &)

julia> parse("export &\na")
ERROR: ParseError("invalid \"export\" statement")
 in parse at ./string.jl:1257

julia> parse("export \$\na")
:(export $(Expr(:$, :a)))

[JeffBezanson]

It's debatable whether parse-unary-prefix should do that, but there's no particular reason for export etc. to call parse-unary-prefix, so we have to fix export/import first. I'd fix it just for export/import.

[yuyichao]

I'm just trying not to duplicate code. OK. I can special case export/import. (after dinner)

[JeffBezanson]

Thanks.