Add some asserts.

Author: ehuss

src/cargo/core/compiler/timings.rs

@@ -162,18 +162,24 @@ impl<'a, 'cfg> Timings<'a, 'cfg> {
 
     /// Mark that the `.rmeta` file as generated.
     pub fn unit_rmeta_finished(&mut self, id: u32, unlocked: Vec<&Unit<'a>>) {
+        // `id` may not always be active. "fresh" units unconditionally
+        // generate `Message::Finish`, but this active map only tracks dirty
+        // units.
         if let Some(unit_time) = self.active.get_mut(&id) {
             let t = d_as_f64(self.start.elapsed());
             unit_time.rmeta_time = Some(t - unit_time.start);
+            assert!(unit_time.unlocked_rmeta_units.is_empty());
             unit_time.unlocked_rmeta_units.extend(unlocked);
         }
     }
 
     /// Mark that a unit has finished running.
     pub fn unit_finished(&mut self, id: u32, unlocked: Vec<&Unit<'a>>) {
+        // See note above in `unit_rmeta_finished`, this may not always be active.
         if let Some(mut unit_time) = self.active.remove(&id) {
             let t = d_as_f64(self.start.elapsed());
             unit_time.duration = t - unit_time.start;
+            assert!(unit_time.unlocked_units.is_empty());
             unit_time.unlocked_units.extend(unlocked);
             if self.report_info {
                 let msg = format!(