67 lines
1.6 KiB
Rust
67 lines
1.6 KiB
Rust
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// <binding_pattern> ::= Symbol { <tight_binding_pattern> }
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// <tight_binding_pattern> ::= Literal
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// | Symbol
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// | OpenParen <binding_pattern> CloseParen
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use std::mem::{discriminant, Discriminant};
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use crate::token::{Literal, Token};
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use super::{Parsable, ParseError, WrappedLexer, absorb_token_or_error};
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#[derive(Debug)]
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pub enum TightBindingPattern {
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Literal(Literal),
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Symbol(String),
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Group(BindingPattern),
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}
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impl Parsable for TightBindingPattern {
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fn expected() -> (Vec<Discriminant<Token>>, bool) {
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(
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vec![
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discriminant(&Token::Literal(Literal::Int(0))),
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discriminant(&Token::Symbol(String::new())),
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discriminant(&Token::OpenParen),
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],
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false,
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)
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}
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fn parse(l: &mut WrappedLexer) -> Result<Self, ParseError> {
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let location = l.span();
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match l.curtok() {
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Token::Literal(l) => Ok(TightBindingPattern::Literal(l.clone())),
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Token::Symbol(name) => Ok(TightBindingPattern::Symbol(name.to_owned())),
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Token::OpenParen => {
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let patt = BindingPattern::parse(l)?;
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absorb_token_or_error(l, discriminant(&Token::CloseParen))?;
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Ok(TightBindingPattern::Group(patt))
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},
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_ => {
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Err(ParseError {
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expected: Self::expected().0,
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location,
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})
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}
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}
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}
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}
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#[derive(Debug)]
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pub struct BindingPattern(String, Vec<TightBindingPattern>);
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impl Parsable for BindingPattern {
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fn expected() -> (Vec<Discriminant<Token>>, bool) {
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(
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vec![
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discriminant(&Token::Symbol(String::new())),
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], false
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)
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}
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fn parse(l: &mut WrappedLexer) -> Result<Self, ParseError> {
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let name = String::parse(l)?;
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let fields = Vec::parse(l)?;
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Ok(Self(name, fields))
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}
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}
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