Joseph Ferano
3295f2f640
Loc.t grows an exclusive end, defaulting to the start, so a location nobody widened is a zero-width span at a point and every existing call site keeps its old meaning. Only the reader knows where a form ends, so only the reader fills them in — one helper in the one place that holds both ends, which is why nothing above Reader had to learn a span exists. The width assertion is the point of the tests: the field could exist, nothing could fill it, and every underline would be one character long while the feature looked finished.
