add assert around sleep_heap() discipline in ticktimer

Every entry into the sleep_heap() should be unique. Any insert()
call that returns a value means we're going to drop a wake-up event.

Add an assert()! that will trigger a panic if this invariant is not
met.

services/xous-ticktimer/src/platform/cramium/implementation.rs

@@ -306,7 +306,7 @@ impl XousTickTimer {
         if let Some(current) = self.stop_interrupt() {
             #[cfg(feature = "debug-print")]
             log::info!("Existing request was {:?}", current);
-            sleep_heap.insert(current.msec, current);
+            assert!(sleep_heap.insert(current.msec, current).is_none(), "Existing sleep_heap entry would be overwritten");
         } else {
             #[cfg(feature = "debug-print")]
             log::info!("There was no existing sleep() request");
@@ -363,7 +363,7 @@ impl XousTickTimer {
 
             #[cfg(feature = "debug-print")]
             log::info!("Modified, the request was: {:?}", request);
-            sleep_heap.insert(request.msec, request);
+            assert!(sleep_heap.insert(request.msec, request).is_none(), "Existing sleep_heap entry would be overwritten");
         } else {
             #[cfg(feature = "debug-print")]
             log::info!("No new sleep request");

services/xous-ticktimer/src/platform/hosted/implementation.rs

@@ -174,7 +174,7 @@ impl XousTickTimer {
         if let Some(current) = self.stop_interrupt() {
             #[cfg(feature = "debug-print")]
             log::info!("Existing request was {:?}", current);
-            sleep_heap.insert(current.msec, current);
+            assert!(sleep_heap.insert(current.msec, current).is_none(), "Existing sleep_heap entry would be overwritten");
         } else {
             #[cfg(feature = "debug-print")]
             log::info!("There was no existing sleep() request");
@@ -231,7 +231,7 @@ impl XousTickTimer {
 
             #[cfg(feature = "debug-print")]
             log::info!("Modified, the request was: {:?}", request);
-            sleep_heap.insert(request.msec, request);
+            assert!(sleep_heap.insert(request.msec, request).is_none(), "Existing sleep_heap entry would be overwritten");
         } else {
             #[cfg(feature = "debug-print")]
             log::info!("No new sleep request");

services/xous-ticktimer/src/platform/precursor/implementation.rs

@@ -287,7 +287,7 @@ impl XousTickTimer {
         if let Some(current) = self.stop_interrupt() {
             #[cfg(feature = "debug-print")]
             log::info!("Existing request was {:?}", current);
-            sleep_heap.insert(current.msec, current);
+            assert!(sleep_heap.insert(current.msec, current).is_none(), "Existing sleep_heap entry would be overwritten");
         } else {
             #[cfg(feature = "debug-print")]
             log::info!("There was no existing sleep() request");
@@ -344,7 +344,7 @@ impl XousTickTimer {
 
             #[cfg(feature = "debug-print")]
             log::info!("Modified, the request was: {:?}", request);
-            sleep_heap.insert(request.msec, request);
+            assert!(sleep_heap.insert(request.msec, request).is_none(), "Existing sleep_heap entry would be overwritten");
         } else {
             #[cfg(feature = "debug-print")]
             log::info!("No new sleep request");