Could using X as Y be syntactic sugar for using X; const global Y = X

[DilumAluthge]

The syntax using X as Y currently throws a syntax error:

julia> using DataFrames as df
ERROR: syntax: invalid syntax "using DataFrames as ..."
Stacktrace:
 [1] top-level scope
   @ none:1

Would it be possible for using DataFrames as df to be syntactic sugar for this:

using DataFrames
const global DataFrames = df

[DilumAluthge]

@JeffBezanson (since you authored #37396) and @fredrikekre (since you wrote ImportMacros.jl)

Any thoughts?

[DilumAluthge]

This is basically what ImportMacros.jl does right now when you do this:

using ImportMacros

@using DataFrames as df

But since the ImportMacros.jl package has been deprecated, I figured it'd be nice to have this syntactic sugar in Julia.

[jebej]

If you need a qualifier (df), it seems more consistent to just import DataFrames as df and use df.fun everywhere.

[stevengj]

See also #1255

[fredrikekre]

This was discussed and decided against in #37396, no? #37396 (comment) and the two following comments.

[StefanKarpinski]

The meaning that would seems to make sense for using DataFrames as DF would be to make it the same as using DataFrames but importing the name DataFrames itself as DF.

[DilumAluthge]

The meaning that would seems to make sense for using DataFrames as DF would be to make it the same as using DataFrames but importing the name DataFrames as DF.

Yeah, that's exactly what I had in mind.

[nickrobinson251]

This was the first thing i tried when i read about the ... as ... syntax in Julia v1.6 (using PowerSystems as PSY) and was surprised it didn't work (as short-hand for using PowerSystems; const PSY = PowerSystems, but without the PowerSystems name also in-scope).

Is there some other behaviour that could have been expected such that using X as Y is ambiguous in some way?

[oxinabox]

For this to be really useful It can't literally be syntactic sugar for using X; const global Y = X
because if X clashes with a variable that is in-scope then you can't load the package in the first place.
import X as Y doesn't have that problem.

Instead it needs to never bring the module's actual name into scope; and create a new name for it

julia> Pipe  # use this so it is incope
Pipe

julia> import Pipe as P2  # no problem

julia> using Pipe
WARNING: using Pipe.Pipe in module Main conflicts with an existing identifier.
ERROR: importing Pipe into Main conflicts with an existing identifier