`outer` keyword triggers a warning

[laggvar]

Creating a cell with the content

function f()
   i = 0
   for outer i = 1:3
       # empty
   end
   return i
end

results in a warning in the REPL running Pluto

┌ Warning: unknown use of `=`. Assignee is unrecognised.
│   ex = :($(Expr(:outer, :i)))
└ @ ExpressionExplorer C:\Users\...\.julia\packages\ExpressionExplorer\ySMFM\src\explore.jl:177

The example was taken directly from the Julia manual https://docs.julialang.org/en/v1/base/base/#outer

Tested with ExpressionExplorer 1.1.2.

[fonsp]

It looks like outer requires the variable to be defined already

➜  ~ julia --pkgimages=no
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.5 (2025-04-14)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> for outer a = 1:3
       end
ERROR: syntax: no outer local variable declaration exists for "for outer"
Stacktrace:
 [1] top-level scope
   @ REPL[1]:1

So we might be able to just ignore it? I think from the ExpressionExplorer perspective, any valid code with or without outer gives the same ReactiveNode.

Maybe someone can write a couple cases to check that this is true?

[laggvar]

I tried the following examples

The first two cases are not controversial, so just removing the warning seems sane to me.

In the case of globals, the current behavior seems equivalent to creating a local copy of i inside the begin block (but errors if i is not declared in another cell). Perhaps it would make more sense if it behaves like a reassignment to the global i, which would lead to an automatic disabling of the other assigning cell. That would be a breaking change though. One option is to warn if i is not defined as a local of the same cell as where outer is used and not warn otherwise?