pest_meta/optimizer/
skipper.rs

Help
1// pest. The Elegant Parser
2// Copyright (c) 2018 Dragoș Tiselice
3//
4// Licensed under the Apache License, Version 2.0
5// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
6// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7// option. All files in the project carrying such notice may not be copied,
8// modified, or distributed except according to those terms.
9
10use std::collections::HashMap;
11
12use crate::ast::*;
13
14pub fn skip(rule: Rule, map: &HashMap<String, Expr>) -> Rule {
15    fn populate_choices(
16        expr: Expr,
17        map: &HashMap<String, Expr>,
18        mut choices: Vec<String>,
19    ) -> Option<Expr> {
20        match expr {
21            Expr::Choice(lhs, rhs) => {
22                if let Expr::Str(string) = *lhs {
23                    choices.push(string);
24                    populate_choices(*rhs, map, choices)
25                } else if let Expr::Ident(name) = *lhs {
26                    // Try inlining rule in choices
27                    if let Some(Expr::Skip(mut inlined_choices)) = map
28                        .get(&name)
29                        .and_then(|expr| populate_choices(expr.clone(), map, vec![]))
30                    {
31                        choices.append(&mut inlined_choices);
32                        populate_choices(*rhs, map, choices)
33                    } else {
34                        None
35                    }
36                } else {
37                    None
38                }
39            }
40            Expr::Str(string) => {
41                choices.push(string);
42                Some(Expr::Skip(choices))
43            }
44            // Try inlining single rule
45            Expr::Ident(name) => map
46                .get(&name)
47                .and_then(|expr| populate_choices(expr.clone(), map, choices)),
48            _ => None,
49        }
50    }
51
52    let Rule { name, ty, expr } = rule;
53    Rule {
54        name,
55        ty,
56        expr: if ty == RuleType::Atomic {
57            expr.map_top_down(|expr| {
58                if let Expr::Rep(expr) = expr.clone() {
59                    if let Expr::Seq(lhs, rhs) = *expr {
60                        if let (Expr::NegPred(expr), Expr::Ident(ident)) = (*lhs, *rhs) {
61                            if ident == "ANY" {
62                                if let Some(expr) = populate_choices(*expr, map, vec![]) {
63                                    return expr;
64                                }
65                            }
66                        }
67                    }
68                };
69
70                expr
71            })
72        } else {
73            expr
74        },
75    }
76}
pest_meta/optimizer/skipper.rs

pest_meta/optimizer/
skipper.rs
