fix the use of end and begin as part of indexing

[schlichtanders]

This is part of a little memory-leak bug which was hard to debug.

Because begin and end had been identified as normal variable names, the use of it inside indexing causes new workspaces to be created.

I guess in normal Pluto this is not so decisive, as anyway a new workspace is created every time, but in my fork I am reusing workspaces where this appeared then.

Maybe it also helps normal Pluto users somehow.

[Pangoraw]

One can use var"begin" anywhere so ideally this behavior should be enabled only inside indexing.

julia> let
           var"begin" = 2
           x = [1,2,3]
           x[var"begin"]
       end
1

[fonsp]

So let's add a flag is_inside_index to ScopeState?

[fonsp]

@schlichtanders Could you make that change? We also need some tests, about begin inside an index, and begin as a variable like the evil example the Paul gave.

[fonsp]

We're so close!

[schlichtanders]

Hi, yes I can make these changes. It is just that I probably will find time around December. As other things are currently quite high in priority.

[Pangoraw]

Related news in Julia: JuliaLang/JuliaSyntax.jl#537.