Struct rustc_pattern_analysis::usefulness::Matrix

struct Matrix<'p, Cx: TypeCx> {
    rows: Vec<MatrixRow<'p, Cx>>,
    place_ty: SmallVec<[Cx::Ty; 2]>,
    place_validity: SmallVec<[ValidityConstraint; 2]>,
    wildcard_row_is_relevant: bool,
}

A 2D matrix. Represents a list of pattern-tuples under investigation.

Invariant: each row must have the same length, and each column must have the same type.

Invariant: the first column must not contain or-patterns. This is handled by Matrix::expand_and_push.

In fact each column corresponds to a place inside the scrutinee of the match. E.g. after specializing (,) and Some on a pattern of type (Option<u32>, bool), the first column of the matrix will correspond to scrutinee.0.Some.0 and the second column to scrutinee.1.

Fields

rows: Vec<MatrixRow<'p, Cx>>

Vector of rows. The rows must form a rectangular 2D array. Moreover, all the patterns of each column must have the same type. Each column corresponds to a place within the scrutinee.

place_ty: SmallVec<[Cx::Ty; 2]>

Track the type of each column/place.

place_validity: SmallVec<[ValidityConstraint; 2]>

Track for each column/place whether it contains a known valid value.

wildcard_row_is_relevant: bool

Track whether the virtual wildcard row used to compute exhaustiveness is relevant. See top of the file for details on relevancy.

Implementations

impl<'p, Cx: TypeCx> Matrix<'p, Cx>

fn expand_and_push(&mut self, row: MatrixRow<'p, Cx>)

Pushes a new row to the matrix. If the row starts with an or-pattern, this recursively expands it. Internal method, prefer Matrix::new.

fn new( arms: &[MatchArm<'p, Cx>], scrut_ty: Cx::Ty, scrut_validity: ValidityConstraint ) -> Self

Build a new matrix from an iterator of MatchArms.

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

fn column_count(&self) -> usize

fn rows( &self ) -> impl Iterator<Item = &MatrixRow<'p, Cx>> + Clone + DoubleEndedIterator + ExactSizeIterator

fn rows_mut( &mut self ) -> impl Iterator<Item = &mut MatrixRow<'p, Cx>> + DoubleEndedIterator + ExactSizeIterator

fn heads( &self ) -> impl Iterator<Item = PatOrWild<'p, Cx>> + Clone + Captures<'_>

Iterate over the first pattern of each row.

fn specialize_constructor( &self, pcx: &PlaceCtxt<'_, 'p, Cx>, ctor: &Constructor<Cx>, ctor_is_relevant: bool ) -> Matrix<'p, Cx>

This computes specialize(ctor, self). See top of the file for explanations.

Trait Implementations

impl<'p, Cx: Clone + TypeCx> Clone for Matrix<'p, Cx>

where Cx::Ty: Clone,

fn clone(&self) -> Matrix<'p, Cx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'p, Cx: TypeCx> Debug for Matrix<'p, Cx>

Pretty-printer for matrices of patterns, example:

+ _     + []                +
+ true  + [First]           +
+ true  + [Second(true)]    +
+ false + [_]               +
+ _     + [_, _, tail @ ..] +
| ✓     | ?                 | // column validity

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.