Struct rustc_pattern_analysis::pat::DeconstructedPat

pub struct DeconstructedPat<Cx: TypeCx> {
    ctor: Constructor<Cx>,
    fields: Vec<DeconstructedPat<Cx>>,
    ty: Cx::Ty,
    data: Option<Cx::PatData>,
    useful: Cell<bool>,
}

Values and patterns can be represented as a constructor applied to some fields. This represents a pattern in this form. This also uses interior mutability to keep track of whether the pattern has been found reachable during analysis. For this reason they cannot be cloned. A DeconstructedPat will almost always come from user input; the only exception are some Wildcards introduced during specialization.

Note that the number of fields may not match the fields declared in the original struct/variant. This happens if a private or non_exhaustive field is uninhabited, because the code mustn’t observe that it is uninhabited. In that case that field is not included in fields. Care must be taken when converting to/from thir::Pat.

Fields

ctor: Constructor<Cx>

fields: Vec<DeconstructedPat<Cx>>

ty: Cx::Ty

data: Option<Cx::PatData>

Extra data to store in a pattern. None if the pattern is a wildcard that does not correspond to a user-supplied pattern.

useful: Cell<bool>

Whether removing this arm would change the behavior of the match expression.

Implementations

impl<Cx: TypeCx> DeconstructedPat<Cx>

pub fn wildcard(ty: Cx::Ty) -> Self

pub fn new( ctor: Constructor<Cx>, fields: Vec<DeconstructedPat<Cx>>, ty: Cx::Ty, data: Cx::PatData ) -> Self

pub(crate) fn is_or_pat(&self) -> bool

pub fn ctor(&self) -> &Constructor<Cx>

pub fn ty(&self) -> &Cx::Ty

pub fn data(&self) -> Option<&Cx::PatData>

Returns the extra data stored in a pattern. Returns None if the pattern is a wildcard that does not correspond to a user-supplied pattern.

pub fn iter_fields<'a>( &'a self ) -> impl Iterator<Item = &'a DeconstructedPat<Cx>>

pub(crate) fn specialize<'a>( &'a self, other_ctor: &Constructor<Cx>, ctor_arity: usize ) -> SmallVec<[PatOrWild<'a, Cx>; 2]>

Specialize this pattern with a constructor. other_ctor can be different from self.ctor, but must be covered by it.

pub(crate) fn set_useful(&self)

We keep track for each pattern if it was ever useful during the analysis. This is used with redundant_subpatterns to report redundant subpatterns arising from or patterns.

pub(crate) fn is_useful(&self) -> bool

pub(crate) fn redundant_subpatterns(&self) -> Vec<&Self>

Report the subpatterns that were not useful, if any.

fn collect_redundant_subpatterns<'a>(&'a self, subpats: &mut Vec<&'a Self>)

Trait Implementations

impl<Cx: TypeCx> Debug for DeconstructedPat<Cx>

This is best effort and not good enough for a Display impl.

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

Formats the value using the given formatter.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.