Mutation testing left both unconstrained.
sector/mod.rs — set_speed on the Box<dyn> and &mut dyn forwarding impls
could be replaced with an empty body and nothing failed. This one hides
better than the read methods because the trait's own default body is
already a no-op, so a forwarder that swallowed the call is
indistinguishable from a source with no speed control. Consequence is a
silently absent value, not a wrong one: the recovery path lowers read
speed through a damaged region, and a swallowed call leaves the drive
at full speed while the caller believes it slowed down. Routed through
a generic S: SectorSource bound, since a direct call on a &mut dyn
receiver auto-derefs to the vtable and never enters the forwarding body.
progress.rs — 42 survivors. All four percentage accessors could return
a constant, read the wrong byte counter, or have their divide-by-zero
guard inverted. Added exact-value tests (25%, not 'some percentage'),
both sides of each guard, the overshoot clamp, and one test setting all
three disc counters to distinct values at once — without it, a swapped
field still passes every single-counter test.
The Progress blanket impl for closures could return a constant true.
That return value is the cancellation signal, so a constant-true body
makes every closure-based consumer uncancellable.
Each mutation applied, observed red, reverted.
Matthew Jackson
c610285910