Replace trait with enum in Rust (#575)

Async methods on traits require [_Pin<Box<dyn Future>>]_ return types,
which pollute the public API.

Additionally, C# interfaces and Rust traits are not equivalent
abstractions, and traits offer no obvious advantage here.

Since the set of implementors is closed and internal, an enum with
private variants provides the same polymorphism with a cleaner, more
idiomatic Rust API.

Author: nenad1002

samples/rust/audio-transcription-example/src/main.rs

@@ -35,10 +35,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     if !model.is_cached().await? {
         println!("Downloading model...");
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}%");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/foundry-local-webserver/src/main.rs

@@ -34,10 +34,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     if !model.is_cached().await? {
         print!("Downloading model {model_alias}...");
         model
-            .download(Some(Box::new(move |progress: &str| {
+            .download(Some(move |progress: &str| {
                 print!("\rDownloading model... {progress}%");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/native-chat-completions/src/main.rs

@@ -32,10 +32,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     if !model.is_cached().await? {
         println!("Downloading model...");
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}%");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/tool-calling-foundry-local/src/main.rs

@@ -66,10 +66,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     if !model.is_cached().await? {
         println!("Downloading model...");
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}%");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/tutorial-chat-assistant/src/main.rs

@@ -21,10 +21,10 @@ async fn main() -> anyhow::Result<()> {
     if !model.is_cached().await? {
         println!("Downloading model...");
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/tutorial-document-summarizer/src/main.rs

@@ -96,10 +96,10 @@ async fn main() -> anyhow::Result<()> {
     if !model.is_cached().await? {
         println!("Downloading model...");
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/tutorial-tool-calling/src/main.rs

@@ -199,10 +199,10 @@ async fn main() -> anyhow::Result<()> {
     if !model.is_cached().await? {
         println!("Downloading model...");
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

samples/rust/tutorial-voice-to-text/src/main.rs

@@ -28,10 +28,10 @@ async fn main() -> anyhow::Result<()> {
     if !speech_model.is_cached().await? {
         println!("Downloading speech model...");
         speech_model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }
@@ -60,10 +60,10 @@ async fn main() -> anyhow::Result<()> {
     if !chat_model.is_cached().await? {
         println!("Downloading chat model...");
         chat_model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 print!("\r  {progress}");
                 io::stdout().flush().ok();
-            })))
+            }))
             .await?;
         println!();
     }

sdk/rust/examples/chat_completion.rs

@@ -40,9 +40,9 @@ async fn main() -> Result<()> {
     if !model.is_cached().await? {
         println!("Downloading model '{}'…", model.alias());
         model
-            .download(Some(Box::new(|progress: &str| {
+            .download(Some(|progress: &str| {
                 println!("  {progress}");
-            })))
+            }))
             .await?;
     }
 

sdk/rust/examples/interactive_chat.rs

@@ -41,7 +41,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     // Download if needed
     if !model.is_cached().await? {
         println!("Downloading '{alias}'…");
-        model.download(Some(Box::new(|p: &str| print!("\r  {p}%")))).await?;
+        model.download(Some(|p: &str| print!("\r  {p}%"))).await?;
         println!();
     }