enum LockstepIterSize {
Expand description

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).



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).


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


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


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

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.


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:

  • Unconstrained: 0 bytes
  • Constraint: 20 bytes
  • Contradiction: 28 bytes