Function dash_path 

pub fn dash_path(path: &BezPath, dash: DashPattern) -> BezPath

path expanded into the sub-paths dash breaks it into.

Both ends of the expansion go through well_formed. The input needs it because kurbo::dash mishandles a subpath that closes without ever producing a segment: it emits that subpath’s closing element ahead of the MoveTo meant to open the output, so a path whose first subpath is a zero-length closed one (a dashed arc at zero sweep records exactly that) dashes to a sequence beginning with ClosePath. Such a sequence is not a path any consumer can read — BezPath’s own “begins with MoveTo” invariant is asserted in a debug build and silently strokes malformed geometry in a release one. Normalizing those subpaths away first removes the input the iterator gets wrong; normalizing the result as well makes the well-formedness of what this returns a property of this function rather than of the dash iterator’s internal states.

Callers inside this crate only ever reach dash here once dash_cycle_is_normalizable has passed it, since kurbo::dash itself does not bound its catch-up loop against a non-normalizable cycle; a caller outside the up-front walk carries that same obligation. Made pub (rather than pub(crate)) so frust-testing’s CPU oracle, which keeps its own independent copy of this lowering (see that crate’s oracle_cpu module docs for why), can pin its output against this one directly rather than only through a rendered image.