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// pest. The Elegant Parser
// Copyright (c) 2018 Dragoș Tiselice
//
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. All files in the project carrying such notice may not be copied,
// modified, or distributed except according to those terms.
use crate::ast::*;
pub fn skip(rule: Rule) -> Rule {
fn populate_choices(expr: Expr, mut choices: Vec<String>) -> Option<Expr> {
match expr {
Expr::Choice(lhs, rhs) => {
if let Expr::Str(string) = *lhs {
choices.push(string);
populate_choices(*rhs, choices)
} else {
None
}
}
Expr::Str(string) => {
choices.push(string);
Some(Expr::Skip(choices))
}
_ => None,
}
}
let Rule { name, ty, expr } = rule;
Rule {
name,
ty,
expr: if ty == RuleType::Atomic {
expr.map_top_down(|expr| {
// TODO: Use box syntax when it gets stabilized.
if let Expr::Rep(expr) = expr.clone() {
if let Expr::Seq(lhs, rhs) = *expr {
if let (Expr::NegPred(expr), Expr::Ident(ident)) = (*lhs, *rhs) {
if ident == "ANY" {
if let Some(expr) = populate_choices(*expr, vec![]) {
return expr;
}
}
}
}
};
expr
})
} else {
expr
},
}
}
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