Struct jrsonnet_gc::GcCellRefMut

pub struct GcCellRefMut<'a, T: Trace + ?Sized + 'static, U: ?Sized = T> { /* fields omitted */ }

A wrapper type for a mutably borrowed value from a GcCell<T>.

Implementations

impl<'a, T: Trace + ?Sized, U: ?Sized> GcCellRefMut<'a, T, U>

pub fn map<V, F>(orig: Self, f: F) -> GcCellRefMut<'a, T, V> where
    V: ?Sized,
    F: FnOnce(&mut U) -> &mut V, 

Makes a new GcCellRefMut for a component of the borrowed data, e.g., an enum variant.

The GcCellRefMut is already mutably borrowed, so this cannot fail.

This is an associated function that needs to be used as GcCellRefMut::map(...). A method would interfere with methods of the same name on the contents of a GcCell used through Deref.

Examples

use jrsonnet_gc::{GcCell, GcCellRefMut};

let c = GcCell::new((5, 'b'));
{
    let b1: GcCellRefMut<(u32, char)> = c.borrow_mut();
    let mut b2: GcCellRefMut<(u32, char), u32> = GcCellRefMut::map(b1, |t| &mut t.0);
    assert_eq!(*b2, 5);
    *b2 = 42;
}
assert_eq!(*c.borrow(), (42, 'b'));

Trait Implementations

impl<'a, T: Trace + ?Sized, U: Debug + ?Sized> Debug for GcCellRefMut<'a, T, U>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, T: Trace + ?Sized, U: ?Sized> Deref for GcCellRefMut<'a, T, U>

type Target = U

The resulting type after dereferencing.

fn deref(&self) -> &U

Dereferences the value.

impl<'a, T: Trace + ?Sized, U: ?Sized> DerefMut for GcCellRefMut<'a, T, U>

fn deref_mut(&mut self) -> &mut U

Mutably dereferences the value.

impl<'a, T: Trace + ?Sized, U: Display + ?Sized> Display for GcCellRefMut<'a, T, U>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, T: Trace + ?Sized, U: ?Sized> Drop for GcCellRefMut<'a, T, U>

fn drop(&mut self)

Executes the destructor for this type.