fix typos in comments

Author: dwrensha

capnp/src/message.rs

@@ -959,7 +959,7 @@ unsafe impl Allocator for ScratchSpaceHeapAllocator<'_> {
     }
 }
 
-/// An Allocator whose first and only segment is a backed by a user-provided buffer.
+/// An Allocator whose first and only segment is backed by a user-provided buffer.
 /// If the segment fills up, subsequent allocations trigger panics.
 ///
 /// The main purpose of this struct is to be used in situations where heap allocation

capnp/src/private/arena.rs

@@ -240,7 +240,7 @@ pub struct BuilderArenaImplInner<A>
 where
     A: Allocator,
 {
-    allocator: Option<A>, // None if has already be deallocated.
+    allocator: Option<A>, // None if has already been deallocated.
     segments: BuilderSegmentArray,
 }
 

capnp/src/private/read_limiter.rs

@@ -49,7 +49,7 @@ mod sync {
         #[inline]
         pub fn can_read(&self, amount: usize) -> Result<()> {
             // We use separate AtomicUsize::load() and AtomicUsize::store() steps, which may
-            // result in undercounting reads if multiple threads are reading at the same.
+            // result in undercounting reads if multiple threads are reading at the same time.
             // That's okay -- a denial of service attack will eventually hit the limit anyway.
             //
             // We could instead do a single fetch_sub() step, but that seems to be slower.