Improve assertion messages (#349)

src/bytes.rs

@@ -209,8 +209,18 @@ impl Bytes {
             Bound::Unbounded => len,
         };
 
-        assert!(begin <= end);
+        assert!(
-        assert!(end <= len);
+            begin <= end,
+            "range start must not be greater than end: {:?} <= {:?}",
+            begin,
+            end,
+        );
+        assert!(
+            end <= len,
+            "range end out of bounds: {:?} <= {:?}",
+            end,
+            len,
+        );
 
         if end == begin {
             return Bytes::new();
@@ -302,7 +312,12 @@ impl Bytes {
     /// Panics if `at > len`.
     #[must_use = "consider Bytes::truncate if you don't need the other half"]
     pub fn split_off(&mut self, at: usize) -> Bytes {
-        assert!(at <= self.len());
+        assert!(
+            at <= self.len(),
+            "split_off out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
 
         if at == self.len() {
             return Bytes::new();
@@ -346,7 +361,12 @@ impl Bytes {
     /// Panics if `at > len`.
     #[must_use = "consider Bytes::advance if you don't need the other half"]
     pub fn split_to(&mut self, at: usize) -> Bytes {
-        assert!(at <= self.len());
+        assert!(
+            at <= self.len(),
+            "split_to out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
 
         if at == self.len() {
             return mem::replace(self, Bytes::new());
@@ -430,7 +450,7 @@ impl Bytes {
     #[inline]
     unsafe fn inc_start(&mut self, by: usize) {
         // should already be asserted, but debug assert for tests
-        debug_assert!(self.len >= by);
+        debug_assert!(self.len >= by, "internal: inc_start out of bounds");
         self.len -= by;
         self.ptr = self.ptr.offset(by as isize);
     }
@@ -477,7 +497,13 @@ impl Buf for Bytes {
 
     #[inline]
     fn advance(&mut self, cnt: usize) {
-        assert!(cnt <= self.len(), "cannot advance past `remaining`");
+        assert!(
+            cnt <= self.len(),
+            "cannot advance past `remaining`: {:?} <= {:?}",
+            cnt,
+            self.len(),
+        );
+
         unsafe {
             self.inc_start(cnt);
         }
@@ -921,7 +947,10 @@ unsafe fn shallow_clone_vec(atom: &AtomicPtr<()>, ptr: *const (), buf: *mut u8,
 
     // The pointer should be aligned, so this assert should
     // always succeed.
-    debug_assert!(0 == (shared as usize & KIND_MASK));
+    debug_assert!(
+        0 == (shared as usize & KIND_MASK),
+        "internal: Box<Shared> should have an aligned pointer",
+    );
 
     // Try compare & swapping the pointer into the `arc` field.
     // `Release` is used synchronize with other threads that

src/bytes_mut.rs

@@ -277,7 +277,12 @@ impl BytesMut {
     /// Panics if `at > capacity`.
     #[must_use = "consider BytesMut::truncate if you don't need the other half"]
     pub fn split_off(&mut self, at: usize) -> BytesMut {
-        assert!(at <= self.capacity());
+        assert!(
+            at <= self.capacity(),
+            "split_off out of bounds: {:?} <= {:?}",
+            at,
+            self.capacity(),
+        );
         unsafe {
             let mut other = self.shallow_clone();
             other.set_start(at);
@@ -345,7 +350,12 @@ impl BytesMut {
     /// Panics if `at > len`.
     #[must_use = "consider BytesMut::advance if you don't need the other half"]
     pub fn split_to(&mut self, at: usize) -> BytesMut {
-        assert!(at <= self.len());
+        assert!(
+            at <= self.len(),
+            "split_to out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
 
         unsafe {
             let mut other = self.shallow_clone();
@@ -459,7 +469,7 @@ impl BytesMut {
     /// assert_eq!(&b[..], b"hello world");
     /// ```
     pub unsafe fn set_len(&mut self, len: usize) {
-        debug_assert!(len <= self.cap);
+        debug_assert!(len <= self.cap, "set_len out of bounds");
         self.len = len;
     }
 
@@ -755,7 +765,7 @@ impl BytesMut {
             return;
         }
 
-        debug_assert!(start <= self.cap);
+        debug_assert!(start <= self.cap, "internal: set_start out of bounds");
 
         let kind = self.kind();
 
@@ -794,7 +804,7 @@ impl BytesMut {
 
     unsafe fn set_end(&mut self, end: usize) {
         debug_assert_eq!(self.kind(), KIND_ARC);
-        assert!(end <= self.cap);
+        assert!(end <= self.cap, "set_end out of bounds");
 
         self.cap = end;
         self.len = cmp::min(self.len, end);
@@ -932,7 +942,12 @@ impl Buf for BytesMut {
 
     #[inline]
     fn advance(&mut self, cnt: usize) {
-        assert!(cnt <= self.remaining(), "cannot advance past `remaining`");
+        assert!(
+            cnt <= self.remaining(),
+            "cannot advance past `remaining`: {:?} <= {:?}",
+            cnt,
+            self.remaining(),
+        );
         unsafe { self.set_start(cnt); }
     }