Struct rustc_mir_build::thir::pattern::deconstruct_pat::Fields

pub(super) struct Fields<'p, 'tcx> {
    fields: &'p [DeconstructedPat<'p, 'tcx>],
}

A value can be decomposed into a constructor applied to some fields. This struct represents those fields, generalized to allow patterns in each field. See also Constructor.

This is constructed for a constructor using Fields::wildcards(). The idea is that Fields::wildcards() constructs a list of fields where all entries are wildcards, and then given a pattern we fill some of the fields with its subpatterns. In the following example Fields::wildcards returns [_, _, _, _]. Then in extract_pattern_arguments we fill some of the entries, and the result is [Some(0), _, _, _].

let x: [Option<u8>; 4] = foo();
match x {
    [Some(0), ..] => {}
}

Note that the number of fields of a constructor 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. For that reason, when you have a FieldIdx you must use index_with_declared_idx.

Fields

fields: &'p [DeconstructedPat<'p, 'tcx>]

Implementations

impl<'p, 'tcx> Fields<'p, 'tcx>

fn empty() -> Self

fn singleton( cx: &MatchCheckCtxt<'p, 'tcx>, field: DeconstructedPat<'p, 'tcx> ) -> Self

pub(super) fn from_iter( cx: &MatchCheckCtxt<'p, 'tcx>, fields: impl IntoIterator<Item = DeconstructedPat<'p, 'tcx>> ) -> Self

fn wildcards_from_tys( cx: &MatchCheckCtxt<'p, 'tcx>, tys: impl IntoIterator<Item = Ty<'tcx>>, span: Span ) -> Self

fn list_variant_nonhidden_fields<'a>( cx: &'a MatchCheckCtxt<'p, 'tcx>, ty: Ty<'tcx>, variant: &'a VariantDef ) -> impl Iterator<Item = (FieldIdx, Ty<'tcx>)> + Captures<'a> + Captures<'p>

pub(super) fn wildcards( pcx: &PatCtxt<'_, 'p, 'tcx>, constructor: &Constructor<'tcx> ) -> Self

Creates a new list of wildcard fields for a given constructor. The result must have a length of constructor.arity().

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

Returns the list of patterns.

Trait Implementations

impl<'p, 'tcx> Clone for Fields<'p, 'tcx>

fn clone(&self) -> Fields<'p, 'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'p, 'tcx> Debug for Fields<'p, 'tcx>

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

Formats the value using the given formatter.

impl<'p, 'tcx> Copy for Fields<'p, '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: 16 bytes