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add eat methods

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This commit is contained in:
Aleksey Kladov 2019-01-31 11:30:21 +03:00
parent e28a5e048a
commit f3489e8111
1 changed files with 23 additions and 6 deletions
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29
crates/ra_hir/src/macros/mbe.rs
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@ -85,16 +85,15 @@ pub(crate) fn parse(tt: &tt::Subtree) -> Option<MacroRules> {
}
fn parse_rule(p: &mut RulesParser) -> Option<Rule> {
let lhs = match p.current()? {
tt::TokenTree::Subtree(sub) => parse_subtree(sub)?,
_ => return None,
};
let rhs = unimplemented!();
let lhs = parse_subtree(p.eat_subtree()?)?;
p.eat_punct('=');
p.eat_punct('>');
let rhs = parse_subtree(p.eat_subtree()?)?;
Some(Rule { lhs, rhs })
}
fn parse_subtree(tt: &tt::Subtree) -> Option<Subtree> {
unimplemented!()
None
}
struct RulesParser<'a> {
@ -118,4 +117,22 @@ impl<'a> RulesParser<'a> {
fn bump(&mut self) {
self.pos += 1;
}
fn eat_subtree(&mut self) -> Option<&'a tt::Subtree> {
match self.current()? {
tt::TokenTree::Subtree(sub) => {
self.bump();
Some(sub)
}
_ => return None,
}
}
fn eat_punct(&mut self, char: char) -> Option<()> {
match self.current()? {
tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: c })) if *c == char => {
self.bump();
Some(())
}
_ => None,
}
}
}