Make AsyncProducer::wait_vacant mutable, bump major version because i…

…t's a breaking change

async/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "async-ringbuf"
-version = "0.2.1"
+version = "0.3.0"
 edition.workspace = true
 authors.workspace = true
 description = "Async SPSC FIFO ring buffer"

async/src/traits/consumer.rs

@@ -29,6 +29,8 @@ pub trait AsyncConsumer: Consumer {
     /// Wait for the buffer to contain at least `count` items or to close.
     ///
     /// In debug mode panics if `count` is greater than buffer capacity.
+    ///
+    /// The method takes `&mut self` because only single [`WaitOccupiedFuture`] is allowed at a time.
     fn wait_occupied(&mut self, count: usize) -> WaitOccupiedFuture<'_, Self> {
         debug_assert!(count <= self.capacity().get());
         WaitOccupiedFuture {

async/src/traits/producer.rs

@@ -45,7 +45,9 @@ pub trait AsyncProducer: Producer {
     /// Wait for the buffer to have at least `count` free places for items or to close.
     ///
     /// In debug mode panics if `count` is greater than buffer capacity.
-    fn wait_vacant(&self, count: usize) -> WaitVacantFuture<'_, Self> {
+    ///
+    /// The method takes `&mut self` because only single [`WaitVacantFuture`] is allowed at a time.
+    fn wait_vacant(&mut self, count: usize) -> WaitVacantFuture<'_, Self> {
         debug_assert!(count <= self.capacity().get());
         WaitVacantFuture {
             owner: self,