Prototype validators API

[matklad]

Implement a tree visitor which can make additional "syntax-like" checks on the tokens and tree produced by the parser.

• [] tree visitor
• [] error builder
• [] testing infrastructure

[aochagavia]

Is there anything like this already in place? I am asking because the issue is old and sometimes changes are introduced without referring to the issue.

[matklad]

Nothing is done yet, though we still need to implement this API.

We have error method here, which returns a Vec<SyntaxError> precisely to allow to compute errors on the fly:

https://github.com/rust-analyzer/rust-analyzer/blob/bc4de7128f474f75a9eff6591923657025099b74/crates/ra_syntax/src/lib.rs#L98

So, what we need is to add a private fn validate(file: &File) -> Vec<SyntaxError> method, and append its results to the errors from the parser.

Here is the subset of things which should be checked by validate:

• string and char literals have closing quote
• char literals are one symbol long
• /* comments have a closing */
• escapes in strings are valid
• doc comments are attached to nodes Should DOC_COMMENT be removed? #166

[aochagavia]

Superseded by #223