boa_engine 0.17.0

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 crate::{object::shape::slot::SlotAttributes, property::PropertyKey, JsObject, JsSymbol};

use super::{SharedShape, TransitionKey};

#[test]
fn test_prune_property_on_counter_limit() {
    let shape = SharedShape::root();

    for i in 0..255 {
        assert_eq!(
            shape.forward_transitions().property_transitions_count(),
            (i, i as u8)
        );

        shape.insert_property_transition(TransitionKey {
            property_key: PropertyKey::Symbol(JsSymbol::new(None).unwrap()),
            attributes: SlotAttributes::all(),
        });
    }

    assert_eq!(
        shape.forward_transitions().property_transitions_count(),
        (255, 255)
    );

    boa_gc::force_collect();

    {
        shape.insert_property_transition(TransitionKey {
            property_key: PropertyKey::Symbol(JsSymbol::new(None).unwrap()),
            attributes: SlotAttributes::all(),
        });
    }

    assert_eq!(
        shape.forward_transitions().property_transitions_count(),
        (1, 0)
    );

    {
        shape.insert_property_transition(TransitionKey {
            property_key: PropertyKey::Symbol(JsSymbol::new(None).unwrap()),
            attributes: SlotAttributes::all(),
        });
    }

    assert_eq!(
        shape.forward_transitions().property_transitions_count(),
        (2, 1)
    );

    boa_gc::force_collect();

    assert_eq!(
        shape.forward_transitions().property_transitions_count(),
        (2, 1)
    );
}

#[test]
fn test_prune_prototype_on_counter_limit() {
    let shape = SharedShape::root();

    assert_eq!(
        shape.forward_transitions().prototype_transitions_count(),
        (0, 0)
    );

    for i in 0..255 {
        assert_eq!(
            shape.forward_transitions().prototype_transitions_count(),
            (i, i as u8)
        );

        shape.change_prototype_transition(Some(JsObject::with_null_proto()));
    }

    boa_gc::force_collect();

    assert_eq!(
        shape.forward_transitions().prototype_transitions_count(),
        (255, 255)
    );

    {
        shape.change_prototype_transition(Some(JsObject::with_null_proto()));
    }

    assert_eq!(
        shape.forward_transitions().prototype_transitions_count(),
        (1, 0)
    );

    {
        shape.change_prototype_transition(Some(JsObject::with_null_proto()));
    }

    assert_eq!(
        shape.forward_transitions().prototype_transitions_count(),
        (2, 1)
    );

    boa_gc::force_collect();

    assert_eq!(
        shape.forward_transitions().prototype_transitions_count(),
        (2, 1)
    );
}