[Feature Requst] Methods for converting strings to nodes and tokens

[duskmoon314]

Hi. I'm trying to implement a parser for a mini-language in the way that rust-analyzer's syntax crate does. To be more specific, the language is a kind of subset of C. Thus there are no trailing commas. When I want to generate code for a list like (Node (',' Node)*), I find there are no ways to convert a string to a token that presents a comma.

Am I missing any APIs? If not, is it possible to add two methods to convert strings to nodes or tokens?

I did a little bit of simple experimentation and this may work:

impl Grammar {
    ...

    /// Returns a node with given name
    pub fn get_node(&self, name: &str) -> Option<Node> {
        self.nodes.iter().position(|n| n.name == name).map(Node)
    }

    /// Returns a token with given name
    pub fn get_token(&self, name: &str) -> Option<Token> {
        self.tokens.iter().position(|t| t.name == name).map(Token)
    }
}

And an example working on ungrammar.ungram:

let n = grammar.get_node("Rule");
println!("Get n {:?}", n);

let t = grammar.get_token(":");
println!("Get t {:?}", t);

Get n Some(Node(2))
Get t Some(Token(8))

I'm not sure whether this is appropriate. If it is appropriate, I can submit a PR.