`esc` asymmetry between `public` and `export`

General Usage
1

I think I understood the semantic difference between export and public.

However, besides this semantic difference I thought that I can always exchange them syntactically. However, this does not seem to be the case.

In the following, only @mypublic fails with ERROR: syntax: malformed "public" statement, while @myexport does not result in an error (tested both on 1.11.4 and nightly).

macro mypublic()
    Expr(:public, :a)
end
@mypublic

macro mypublic_esc()
    Expr(:public, :a) |> esc
end
@mypublic_esc
 
macro myexport()
    Expr(:export, :a)
end
@myexport

macro myexport_esc()
    Expr(:export, :a) |> esc
end
@myexport_esc

Why is this the case? Where is this difference documented?

2

Some of the asymmetry between public and export is explained in the comments to Make `public` parse similar to `export` · Issue #502 · JuliaLang/JuliaSyntax.jl · GitHub. I suspect there are similar reasons for this discrepancy.

1 Like
3

Thanks, very enlightening. However, I keep it open for the moment, as the linked discussion focuses on global scope vs local scope, which does not seem to apply here. Although the motivation is probably similar, I would still like to understand the motivation for the difference with esc.