boa_engine 0.22.0

Boa is a Javascript lexer, parser and compiler written in Rust. Currently, it has support for some of the language.
Documentation 
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use super::RegisterOperand;
use crate::{Context, builtins::Array, vm::opcode::Operation};

/// `RestParameterInit` implements the Opcode Operation for `Opcode::RestParameterInit`
///
/// Operation:
///  - Initialize the rest parameter value of a function from the remaining arguments.
#[derive(Debug, Clone, Copy)]
pub(crate) struct RestParameterInit;

impl RestParameterInit {
    #[inline(always)]
    pub(super) fn operation(dst: RegisterOperand, context: &mut Context) {
        let array = if let Some(rest) = context
            .vm
            .stack
            .pop_rest_arguments(context.vm.frames.last().expect("frame must exist"))
        {
            let rest_count = rest.len() as u32;
            let array = Array::create_array_from_list(rest, context);
            context.vm.frame_mut().argument_count -= rest_count;
            // Adjust rp since draining rest arguments shifted the register slots down.
            context.vm.frame_mut().rp -= rest_count;
            array
        } else {
            Array::array_create(0, None, context).expect("could not create an empty array")
        };
        context.vm.set_register(dst.into(), array.into());
    }
}

impl Operation for RestParameterInit {
    const NAME: &'static str = "RestParameterInit";
    const INSTRUCTION: &'static str = "INST - RestParameterInit";
    const COST: u8 = 6;
}