Enum rustc_mir_build::thir::pattern::deconstruct_pat::Constructor

pub(super) enum Constructor<'tcx> {
    Single,
    Variant(VariantIdx),
    IntRange(IntRange),
    FloatRange(ConstantKind<'tcx>, ConstantKind<'tcx>, RangeEnd),
    Str(ConstantKind<'tcx>),
    Slice(Slice),
    Opaque,
    NonExhaustive,
    Missing {
        nonexhaustive_enum_missing_real_variants: bool,
    },
    Wildcard,
    Or,
}

A value can be decomposed into a constructor applied to some fields. This struct represents the constructor. See also Fields.

pat_constructor retrieves the constructor corresponding to a pattern. specialize_constructor returns the list of fields corresponding to a pattern, given a constructor. Constructor::apply reconstructs the pattern from a pair of Constructor and Fields.

Variants

Single

The constructor for patterns that have a single constructor, like tuples, struct patterns and fixed-length arrays.

Variant(VariantIdx)

Enum variants.

IntRange(IntRange)

Ranges of integer literal values (2, 2..=5 or 2..5).

FloatRange(ConstantKind<'tcx>, ConstantKind<'tcx>, RangeEnd)

Ranges of floating-point literal values (2.0..=5.2).

Str(ConstantKind<'tcx>)

String literals. Strings are not quite the same as &[u8] so we treat them separately.

Slice(Slice)

Array and slice patterns.

Opaque

Constants that must not be matched structurally. They are treated as black boxes for the purposes of exhaustiveness: we must not inspect them, and they don’t count towards making a match exhaustive.

NonExhaustive

Fake extra constructor for enums that aren’t allowed to be matched exhaustively. Also used for those types for which we cannot list constructors explicitly, like f64 and str.

Missing

Fields

nonexhaustive_enum_missing_real_variants: bool

Stands for constructors that are not seen in the matrix, as explained in the documentation for SplitWildcard. The carried bool is used for the non_exhaustive_omitted_patterns lint.

Wildcard

Wildcard pattern.

Or

Or-pattern.

Implementations

impl<'tcx> Constructor<'tcx>

pub(super) fn is_wildcard(&self) -> bool

pub(super) fn is_non_exhaustive(&self) -> bool

fn as_int_range(&self) -> Option<&IntRange>

fn as_slice(&self) -> Option<Slice>

pub(super) fn is_unstable_variant(&self, pcx: &PatCtxt<'_, '_, 'tcx>) -> bool

Checks if the Constructor is a variant and TyCtxt::eval_stability returns EvalResult::Deny { .. }.

This means that the variant has a stdlib unstable feature marking it.

pub(super) fn is_doc_hidden_variant(&self, pcx: &PatCtxt<'_, '_, 'tcx>) -> bool

Checks if the Constructor is a Constructor::Variant with a #[doc(hidden)] attribute from a type not local to the current crate.

fn variant_index_for_adt(&self, adt: AdtDef<'tcx>) -> VariantIdx

pub(super) fn arity(&self, pcx: &PatCtxt<'_, '_, 'tcx>) -> usize

The number of fields for this constructor. This must be kept in sync with Fields::wildcards.

pub(super) fn split<'a>(
    &self,
    pcx: &PatCtxt<'_, '_, 'tcx>,
    ctors: impl Iterator<Item = &'a Constructor<'tcx>> + Clone
) -> SmallVec<[Self; 1]>where
    'tcx: 'a,

Some constructors (namely Wildcard, IntRange and Slice) actually stand for a set of actual constructors (like variants, integers or fixed-sized slices). When specializing for these constructors, we want to be specialising for the actual underlying constructors. Naively, we would simply return the list of constructors they correspond to. We instead are more clever: if there are constructors that we know will behave the same wrt the current matrix, we keep them grouped. For example, all slices of a sufficiently large length will either be all useful or all non-useful with a given matrix.

See the branches for details on how the splitting is done.

This function may discard some irrelevant constructors if this preserves behavior and diagnostics. Eg. for the _ case, we ignore the constructors already present in the matrix, unless all of them are.

pub(super) fn is_covered_by<'p>(
    &self,
    pcx: &PatCtxt<'_, 'p, 'tcx>,
    other: &Self
) -> bool

Returns whether self is covered by other, i.e. whether self is a subset of other. For the simple cases, this is simply checking for equality. For the “grouped” constructors, this checks for inclusion.

fn is_covered_by_any<'p>(
    &self,
    pcx: &PatCtxt<'_, 'p, 'tcx>,
    used_ctors: &[Constructor<'tcx>]
) -> bool

Faster version of is_covered_by when applied to many constructors. used_ctors is assumed to be built from matrix.head_ctors() with wildcards filtered out, and self is assumed to have been split from a wildcard.

Trait Implementations

impl<'tcx> Clone for Constructor<'tcx>

fn clone(&self) -> Constructor<'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for Constructor<'tcx>

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

Formats the value using the given formatter.

impl<'tcx> PartialEq<Constructor<'tcx>> for Constructor<'tcx>

fn eq(&self, other: &Constructor<'tcx>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'tcx> StructuralPartialEq for Constructor<'tcx>

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: 104 bytes

Size for each variant:

• Single: 0 bytes
• Variant: 7 bytes
• IntRange: 63 bytes
• FloatRange: 103 bytes
• Str: 55 bytes
• Slice: 47 bytes
• Opaque: 0 bytes
• NonExhaustive: 0 bytes
• Missing: 1 byte
• Wildcard: 0 bytes
• Or: 0 bytes