Struct PatternColumn

pub struct PatternColumn<'p, Cx: PatCx> { /* private fields */ }

A column of patterns in a match, where a column is the intuitive notion of “subpatterns that inspect the same subvalue/place”. This is used to traverse patterns column-by-column for lints. Despite similarities with the algorithm in crate::usefulness, this does a different traversal. Notably this is linear in the depth of patterns, whereas compute_exhaustiveness_and_usefulness is worst-case exponential (exhaustiveness is NP-complete). The core difference is that we treat sub-columns separately.

This is not used in the usefulness algorithm; only in lints.

Implementations

impl<'p, Cx: PatCx> PatternColumn<'p, Cx>

pub fn new(arms: &[MatchArm<'p, Cx>]) -> Self

pub fn head_ty(&self) -> Option<&Cx::Ty>

pub fn iter<'a>( &'a self, ) -> impl Iterator<Item = &'p DeconstructedPat<Cx>> + Captures<'a>

pub fn analyze_ctors( &self, cx: &Cx, ty: &Cx::Ty, ) -> Result<SplitConstructorSet<Cx>, Cx::Error>

Do constructor splitting on the constructors of the column.

pub fn specialize( &self, cx: &Cx, ty: &Cx::Ty, ctor: &Constructor<Cx>, ) -> Vec<PatternColumn<'p, Cx>>

Does specialization: given a constructor, this takes the patterns from the column that match the constructor, and outputs their fields. This returns one column per field of the constructor. They usually all have the same length (the number of patterns in self that matched ctor), except that we expand or-patterns which may change the lengths.

Trait Implementations

impl<'p, Cx: Debug + PatCx> Debug for PatternColumn<'p, Cx>

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

Formats the value using the given formatter.