Illustrating alexcrichton/futures-rs/#676

cargo.out

@@ -1,22 +1,22 @@
    Compiling futuretest v0.1.0 (file:///mnt/c/Users/Mahmoud/git/futuretest)
 error[E0271]: type mismatch resolving `<futures::FutureResult<(), std::string::String> as futures::IntoFuture>::Error == &str`
-  --> src/main.rs:13:10
+  --> src/main.rs:12:10
    |
-13 |         .and_then(|_|
+12 |         .and_then(|_|
    |          ^^^^^^^^ expected struct `std::string::String`, found &str
    |
    = note: expected type `std::string::String`
               found type `&str`
 
-error[E0271]: type mismatch resolving `<futures::FutureResult<(), std::string::String> as futures::IntoFuture>::Error == &str`
-  --> src/main.rs:20:10
+error[E0599]: no method named `and_then` found for type `futures::AndThen<futures::MapErr<futures::FutureResult<(), ()>, [closure@src/main.rs:11:18: 11:42]>, futures::FutureResult<(), std::string::String>, [closure@src/main.rs:12:19: 15:14]>` in the current scope
+  --> src/main.rs:17:10
    |
-20 |     core.run(f).unwrap();
-   |          ^^^ expected struct `std::string::String`, found &str
+17 |         .and_then(|_| future::result::<(), String>(Err("another &'static str error".to_owned())))
+   |          ^^^^^^^^
    |
-   = note: expected type `std::string::String`
-              found type `&str`
-   = note: required because of the requirements on the impl of `futures::Future` for `futures::AndThen<futures::Map<futures::MapErr<futures::FutureResult<(), ()>, [closure@src/main.rs:11:18: 11:43]>, [closure@src/main.rs:12:14: 12:67]>, futures::FutureResult<(), std::string::String>, [closure@src/main.rs:13:19: 16:14]>`
+   = note: the method `and_then` exists but the following trait bounds were not satisfied:
+           `futures::AndThen<futures::MapErr<futures::FutureResult<(), ()>, [closure@src/main.rs:11:18: 11:42]>, futures::FutureResult<(), std::string::String>, [closure@src/main.rs:12:19: 15:14]> : futures::Future`
+           `&mut futures::AndThen<futures::MapErr<futures::FutureResult<(), ()>, [closure@src/main.rs:11:18: 11:42]>, futures::FutureResult<(), std::string::String>, [closure@src/main.rs:12:19: 15:14]> : futures::Future`
 
 error: aborting due to 2 previous errors
 

src/main.rs

@@ -7,14 +7,14 @@ use tokio_core::reactor::Core;
 fn main() {
     let mut core = Core::new().expect("Failed to initialize tokio_core reactor!");
 
-    let f = future::result(Ok(()))
-        .map_err(|()| "&'static str error")
-        .map(|_| future::result(Err("another &'static str error")))
+    let f = future::result::<(),()>(Ok(()))
+        .map_err(|_| "&'static str error")
         .and_then(|_|
              future::result(Ok(())
                 .map_err(|()| "String error".to_owned())
             )
         )
+        .and_then(|_| future::result::<(), String>(Err("another &'static str error".to_owned())))
     ;
 
     core.run(f).unwrap();