Enum rustc_mir_build::thir::pattern::usefulness::Usefulness

pub(crate) enum Usefulness<'tcx> {
    Useful(SpanSet),
    UsefulWithWitness(Vec<Witness<'tcx>>),
    NotUseful,
}

Variants

Useful(SpanSet)

Pontentially carries a set of sub-branches that have been found to be unreachable. Used only in the presence of or-patterns, otherwise it stays empty.

UsefulWithWitness(Vec<Witness<'tcx>>)

Carries a list of witnesses of non-exhaustiveness.

NotUseful

Implementations

impl<'tcx> Usefulness<'tcx>

fn new_useful(preference: WitnessPreference) -> Self

fn merge(usefulnesses: impl Iterator<Item = Self>) -> Self

When trying several branches and each returns a Usefulness, we need to combine the results together.

fn unsplit_or_pat(self, this_span: Span, or_pat_spans: &[Span]) -> Self

After calculating the usefulness for a branch of an or-pattern, call this to make this usefulness mergeable with those from the other branches.

fn apply_constructor<'p>(
    self,
    pcx: PatCtxt<'_, 'p, 'tcx>,
    matrix: &Matrix<'p, 'tcx>,
    ctor: &Constructor<'tcx>,
    ctor_wild_subpatterns: &Fields<'p, 'tcx>
) -> Self

After calculating usefulness after a specialization, call this to recontruct a usefulness that makes sense for the matrix pre-specialization. This new usefulness can then be merged with the results of specializing with the other constructors.

Trait Implementations

impl<'tcx> Clone for Usefulness<'tcx>

pub fn clone(&self) -> Usefulness<'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for Usefulness<'tcx>

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

Formats the value using the given formatter.