use to_string instead of format! and change UnsupportedDuplexStream to unit struct rather than making it defensive for future field addition

Author: gulbrand

src/duplex.rs

@@ -259,23 +259,16 @@ impl DuplexStreamConfig {
 /// This type implements `StreamTrait` but all operations return errors.
 /// Backend implementations should replace this with their own type once
 /// duplex support is implemented.
-pub struct UnsupportedDuplexStream {
-    _private: (),
-}
+#[derive(Default)]
+pub struct UnsupportedDuplexStream;
 
 impl UnsupportedDuplexStream {
     /// Create a new unsupported duplex stream marker.
     ///
     /// This should not normally be called - it exists only to satisfy
     /// type requirements for backends without duplex support.
     pub fn new() -> Self {
-        Self { _private: () }
-    }
-}
-
-impl Default for UnsupportedDuplexStream {
-    fn default() -> Self {
-        Self::new()
+        Self
     }
 }
 

src/host/coreaudio/macos/mod.rs

@@ -187,7 +187,7 @@ impl StreamInner {
     fn play(&mut self) -> Result<(), PlayStreamError> {
         if !self.playing {
             if let Err(e) = self.audio_unit.start() {
-                let description = format!("{e}");
+                let description = e.to_string();
                 let err = BackendSpecificError { description };
                 return Err(err.into());
             }
@@ -199,7 +199,7 @@ impl StreamInner {
     fn pause(&mut self) -> Result<(), PauseStreamError> {
         if self.playing {
             if let Err(e) = self.audio_unit.stop() {
-                let description = format!("{e}");
+                let description = e.to_string();
                 let err = BackendSpecificError { description };
                 return Err(err.into());
             }
@@ -288,7 +288,7 @@ impl DuplexStreamInner {
     fn play(&mut self) -> Result<(), PlayStreamError> {
         if !self.playing {
             if let Err(e) = self.audio_unit.start() {
-                let description = format!("{e}");
+                let description = e.to_string();
                 let err = BackendSpecificError { description };
                 return Err(err.into());
             }
@@ -300,7 +300,7 @@ impl DuplexStreamInner {
     fn pause(&mut self) -> Result<(), PauseStreamError> {
         if self.playing {
             if let Err(e) = self.audio_unit.stop() {
-                let description = format!("{e}");
+                let description = e.to_string();
                 let err = BackendSpecificError { description };
                 return Err(err.into());
             }