if first type bound isn't Into<T> auto-box it

1 files changed, 10 insertions, 2 deletions

diff --git a/README.md b/README.md
index 967738e..972f82c 100644
--- a/README.md
+++ b/README.md
@@ -78,6 +78,14 @@ in `E` need to be mapped with `map_err()`. Dynamize also understands
 options and results, so e.g. `Result<Option<Self::Item>, Self::Error>` also
 just works.
 
+The destination type of an associated type is
+determined by looking at its first trait bound:
+
+* `Into<T>` is mapped to `T`
+
+* `SomeTrait` is mapped to `Box<dyn SomeTrait>`  
+  (for this `SomeTrait` of course needs to be object-safe)
+
 ## Dynamize supports async
 
 Dynamize supports async out of the box. Since Rust however does not yet support
@@ -90,7 +98,7 @@ async functions in traits, you'll have to additionally use another library like
 #[blanket_impl_attr(async_trait)]
 #[async_trait]
 trait Client: Sync {
-    type Error: Into<SuperError>;
+    type Error: std::error::Error;
 
     async fn get(&self, url: String) -> Result<Vec<u8>, Self::Error>;
 }
@@ -109,7 +117,7 @@ The following also just works:
 ```rust
 #[dynamize::dynamize]
 trait TraitWithCallback {
-    type A: Into<String>;
+    type A: SomeTrait;
 
     fn fun_with_callback<F: Fn(Self::A)>(&self, a: F);
 }