line numbers in the AST re #732

[ffrank]

I wrote a suggestion of how to store the mcl code coordinates of notable AST nodes in the parser. (It's not done for each last node.)

The approach is possibly flawed; the amount of copy/paste makes me sad.

This was still the easier part though. Next I was trying to figure out how to generate an error message during type unification, that indicates the == operator in the following snippet:

$a = 1
$b = "one"

if $a == $b {
        $c = 3
}

But the unification approach that collects all invariants, and then loops over them, makes this very hard, maybe impossible.

Will we need to keep references to the AST nodes in the invariants? So that we can trace where problematic invariants originate?

[purpleidea]

the amount of copy/paste makes me sad.

I expect some copy-paste, that's to be expected.

during type unification

Don't worry about this at the moment. I have some structural changes which are coming and I don't know if this will break anything that happens there yet, so TBD.

It's not done for each last node.)

Just a POC is fine!

[purpleidea]

PS: Note there is also the %error stuff in parser-- that works well enough. Line numbers in the code is the goal =D

[purpleidea]

Just some random quick thoughts.

[ffrank]

In the latest commit 913c100 the code essentially works. It will store start and end positions in nodes types that have received the TextArea embed.

This does not survive interpolation though, unless Interpolate is adapted as demonstrated for StmtBind and StmtIf here.

I even have an idea for a type unifier that could allow us to drill down to the offensive expressions.

EDIT: after some shy attempts to implement a prototype, I want to say this idea did not pan out. Refactored unification sounds much more promising 👇🏻

[purpleidea]

FYI: I'm currently refactoring the type unification stuff, so after that's done it will be great to revisit this and get it merged in some form. Sneak peak: The new unification has a pointer to the Expr in question so as long as the Expr has the ROW/COL information, then we'll be able to show that without doing any additional plumbing.

[ffrank]

I'm not moving this in any direction until that change lands then.

[purpleidea]

Yeah, sorry for the delay. The start of that is here: https://github.com/purpleidea/mgmt/tree/feat/unification in case you're knowledgeable in this area and want to help. I'm kind of a terrible algorithmist and a few things are up in the air, but if you or anyone is an expert in this area, please chime in =D