Enum rustc_pattern_analysis::usefulness::ValidityConstraint

pub enum ValidityConstraint {
    ValidOnly,
    MaybeInvalid,
    MaybeInvalidButAllowOmittingArms,
}

Serves two purposes:

• in a wildcard, tracks whether the wildcard matches only valid values (i.e. is a binding _a) or also invalid values (i.e. is a true _ pattern).
• in the matrix, track whether a given place (aka column) is known to contain a valid value or not.

Variants

ValidOnly

MaybeInvalid

MaybeInvalidButAllowOmittingArms

Option for backwards compatibility: the place is not known to be valid but we allow omitting useful && !reachable arms anyway.

Implementations

impl ValidityConstraint

pub fn from_bool(is_valid_only: bool) -> Self

fn allow_omitting_side_effecting_arms(self) -> Self

fn is_known_valid(self) -> bool

fn allows_omitting_empty_arms(self) -> bool

fn specialize<Cx: TypeCx>(self, ctor: &Constructor<Cx>) -> Self

If the place has validity given by self and we read that the value at the place has constructor ctor, this computes what we can assume about the validity of the constructor fields.

Pending further opsem decisions, the current behavior is: validity is preserved, except inside & and union fields where validity is reset to MaybeInvalid.

Trait Implementations

impl Clone for ValidityConstraint

fn clone(&self) -> ValidityConstraint

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ValidityConstraint

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

Formats the value using the given formatter.

impl Display for ValidityConstraint

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

Formats the value using the given formatter.

impl PartialEq for ValidityConstraint

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

This method tests for self and other values to be equal, and is used by ==.

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

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

impl Copy for ValidityConstraint

impl Eq for ValidityConstraint

impl StructuralEq for ValidityConstraint

impl StructuralPartialEq for ValidityConstraint

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:

• ValidOnly: 0 bytes
• MaybeInvalid: 0 bytes
• MaybeInvalidButAllowOmittingArms: 0 bytes