Enum rustc_middle::mir::syntax::FakeBorrowKind

pub enum FakeBorrowKind {
    Shallow,
    Deep,
}

Variants

Shallow

A shared shallow borrow. The immediately borrowed place must be immutable, but projections from it don’t need to be. For example, a shallow borrow of a.b doesn’t conflict with a mutable borrow of a.b.c.

This is used when lowering matches: when matching on a place we want to ensure that place have the same value from the start of the match until an arm is selected. This prevents this code from compiling:

let mut x = &Some(0);
match *x {
    None => (),
    Some(_) if { x = &None; false } => (),
    Some(_) => (),
}

This can’t be a shared borrow because mutably borrowing (*x as Some).0 should not checking the discriminant or accessing other variants, because the mutating (*x as Some).0 can’t affect the discriminant of x. E.g. the following is allowed:

let mut x = Some(0);
match x {
    Some(_)
        if {
            if let Some(ref mut y) = x {
                *y += 1;
            };
            true
        } => {}
    _ => {}
}

Deep

A shared (deep) borrow. Data must be immutable and is aliasable.

This is used when lowering deref patterns, where shallow borrows wouldn’t prevent something like:

Trait Implementations

impl Clone for FakeBorrowKind

fn clone(&self) -> FakeBorrowKind

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FakeBorrowKind

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

Formats the value using the given formatter.

impl<__D: TyDecoder> Decodable<__D> for FakeBorrowKind

fn decode(__decoder: &mut __D) -> Self

impl<__E: TyEncoder> Encodable<__E> for FakeBorrowKind

fn encode(&self, __encoder: &mut __E)

impl Hash for FakeBorrowKind

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for FakeBorrowKind

fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher, )

impl Ord for FakeBorrowKind

fn cmp(&self, other: &FakeBorrowKind) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for FakeBorrowKind

fn eq(&self, other: &FakeBorrowKind) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for FakeBorrowKind

fn partial_cmp(&self, other: &FakeBorrowKind) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for FakeBorrowKind

impl Eq for FakeBorrowKind

impl StructuralPartialEq for FakeBorrowKind

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 1 byte

Size for each variant:

• Shallow: 0 bytes
• Deep: 0 bytes