boa_engine 0.16.0

Boa is a Javascript lexer, parser and Just-in-Time compiler written in Rust. Currently, it has support for some of the language.
Documentation 
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#[cfg(test)]
mod tests;

use crate::syntax::{
    ast::{node::FunctionDecl, Keyword},
    parser::{
        statement::declaration::hoistable::{parse_callable_declaration, CallableDeclaration},
        AllowAwait, AllowDefault, AllowYield, Cursor, ParseError, TokenParser,
    },
};
use boa_interner::Interner;
use std::io::Read;

/// Function declaration parsing.
///
/// More information:
///  - [MDN documentation][mdn]
///  - [ECMAScript specification][spec]
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function
/// [spec]: https://tc39.es/ecma262/#prod-FunctionDeclaration

#[derive(Debug, Clone, Copy)]
pub(in crate::syntax::parser) struct FunctionDeclaration {
    allow_yield: AllowYield,
    allow_await: AllowAwait,
    is_default: AllowDefault,
}

impl FunctionDeclaration {
    /// Creates a new `FunctionDeclaration` parser.
    pub(in crate::syntax::parser) fn new<Y, A, D>(
        allow_yield: Y,
        allow_await: A,
        is_default: D,
    ) -> Self
    where
        Y: Into<AllowYield>,
        A: Into<AllowAwait>,
        D: Into<AllowDefault>,
    {
        Self {
            allow_yield: allow_yield.into(),
            allow_await: allow_await.into(),
            is_default: is_default.into(),
        }
    }
}

impl CallableDeclaration for FunctionDeclaration {
    fn error_context(&self) -> &'static str {
        "function declaration"
    }
    fn is_default(&self) -> bool {
        self.is_default.0
    }
    fn name_allow_yield(&self) -> bool {
        self.allow_yield.0
    }
    fn name_allow_await(&self) -> bool {
        self.allow_await.0
    }
    fn parameters_allow_yield(&self) -> bool {
        false
    }
    fn parameters_allow_await(&self) -> bool {
        false
    }
    fn body_allow_yield(&self) -> bool {
        false
    }
    fn body_allow_await(&self) -> bool {
        false
    }
}

impl<R> TokenParser<R> for FunctionDeclaration
where
    R: Read,
{
    type Output = FunctionDecl;

    fn parse(
        self,
        cursor: &mut Cursor<R>,
        interner: &mut Interner,
    ) -> Result<Self::Output, ParseError> {
        cursor.expect((Keyword::Function, false), "function declaration", interner)?;

        let result = parse_callable_declaration(&self, cursor, interner)?;

        Ok(FunctionDecl::new(result.0, result.1, result.2))
    }
}