pub type Increments<'a> = &'a mut dyn FnMut(&Increment);Expand description
Text arriving from a provider before the call has finished.
One argument and no return value, because an increment is not a decision: nothing downstream may branch on it, and a sink that could refuse would make a display detail able to fail a call.
What arrives here is not history. The record of what the model
said is written once, from ModelReturn, after the call settles.
Increments are a thing to look at while waiting, and the two can
disagree — a provider may revise, and a cut stream leaves increments
behind that no ModelReturn ever confirms. Where they disagree the
settled text wins, and that rule is held on the far side of the wire
by the client.