pub unsafe trait TrustedLen: Iterator { }Expand description
Trait for all types which have a known upper-bound.
Functions that receive a TrustedLen iterator can assume that it’s size_hint is exact,
and can pre-allocate memory, unroll loops, or otherwise optimize their implementations
accordingly.
§Safety
The type which implements this trait must provide an exact Some upper-bound for its
size_hint method. Failure to do so can trigger undefined behavior in users of the trait.