Struct rustc_pattern_analysis::usefulness::BranchPatUsefulness

struct BranchPatUsefulness<'p, Cx: PatCx> {
    useful: bool,
    covered_by: FxHashSet<&'p DeconstructedPat<Cx>>,
}

A pattern is a “branch” if it is the immediate child of an or-pattern, or if it is the whole pattern of a match arm. These are the patterns that can be meaningfully considered “redundant”, since e.g. 0 in (0, 1) cannot be redundant on its own.

We track for each branch pattern whether it is useful, and if not why.

Fields

useful: bool

Whether this pattern is useful.

covered_by: FxHashSet<&'p DeconstructedPat<Cx>>

A set of patterns that:

• come before this one in the match;
• intersect this one;
• at the end of the algorithm, if !self.useful, their union covers this pattern.

Implementations

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

fn update(&mut self, row: &MatrixRow<'p, Cx>, matrix: &Matrix<'p, Cx>)

Update self with the usefulness information found in row.

fn is_redundant(&self) -> Option<RedundancyExplanation<'p, Cx>>

Check whether this pattern is redundant, and if so explain why.

Trait Implementations

impl<'p, Cx: PatCx> Default for BranchPatUsefulness<'p, Cx>

fn default() -> Self

Returns the “default value” for a type.

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: 40 bytes