Enum rustc_expand::mbe::macro_parser::NamedMatch

pub(crate) enum NamedMatch {
    MatchedSeq(Vec<NamedMatch>),
    MatchedTokenTree(TokenTree),
    MatchedNonterminal(Lrc<(Nonterminal, Span)>),
}

NamedMatch is a pattern-match result for a single metavar. All MatchedNonterminals in the NamedMatch have the same non-terminal type (expr, item, etc).

The in-memory structure of a particular NamedMatch represents the match that occurred when a particular subset of a matcher was applied to a particular token tree.

The width of each MatchedSeq in the NamedMatch, and the identity of the MatchedNtNonTtss, will depend on the token tree it was applied to: each MatchedSeq corresponds to a single repetition in the originating token tree. The depth of the NamedMatch structure will therefore depend only on the nesting depth of repetitions in the originating token tree it was derived from.

In layperson’s terms: NamedMatch will form a tree representing nested matches of a particular meta variable. For example, if we are matching the following macro against the following invocation…

macro_rules! foo {
  ($($($x:ident),+);+) => {}
}

foo!(a, b, c, d; a, b, c, d, e);

Then, the tree will have the following shape:

MatchedSeq([
  MatchedSeq([
    MatchedNonterminal(a),
    MatchedNonterminal(b),
    MatchedNonterminal(c),
    MatchedNonterminal(d),
  ]),
  MatchedSeq([
    MatchedNonterminal(a),
    MatchedNonterminal(b),
    MatchedNonterminal(c),
    MatchedNonterminal(d),
    MatchedNonterminal(e),
  ])
])

Variants

MatchedSeq(Vec<NamedMatch>)

MatchedTokenTree(TokenTree)

MatchedNonterminal(Lrc<(Nonterminal, Span)>)

Trait Implementations

impl Clone for NamedMatch

fn clone(&self) -> NamedMatch

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for NamedMatch

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

Formats the value using the given formatter.

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: 32 bytes

Size for each variant:

• MatchedSeq: 32 bytes
• MatchedTokenTree: 32 bytes
• MatchedNonterminal: 16 bytes