Enum rustc_expand::mbe::transcribe::LockstepIterSize

pub(in mbe::transcribe) enum LockstepIterSize {
    Unconstrained,
    Constraint(usize, MacroRulesNormalizedIdent),
    Contradiction(String),
}

An accumulator over a TokenTree to be used with fold. During transcription, we need to make sure that the size of each sequence and all of its nested sequences are the same as the sizes of all the matched (nested) sequences in the macro invocation. If they don't match, somebody has made a mistake (either the macro writer or caller).

Variants

Unconstrained

No constraints on length of matcher. This is true for any TokenTree variants except a MetaVar with an actual MatchedSeq (as opposed to a MatchedNonterminal).

Constraint(usize, MacroRulesNormalizedIdent)

A MetaVar with an actual MatchedSeq. The length of the match and the name of the meta-var are returned.

Contradiction(String)

Two Constraints on the same sequence had different lengths. This is an error.

Implementations

impl LockstepIterSize

pub(in mbe::transcribe) fn with(
    self,
    other: LockstepIterSize
) -> LockstepIterSize

Find incompatibilities in matcher/invocation sizes.

• Unconstrained is compatible with everything.
• Contradiction is incompatible with everything.
• Constraint(len) is only compatible with other constraints of the same length.

Trait Implementations

impl Clone for LockstepIterSize

pub fn clone(&self) -> LockstepIterSize

Returns a copy of the value.

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

Performs copy-assignment from source.