Backwards type propagation leads to cryptic errors

In the committed code, the chosen type is from the second error declaration and not the first.
2017-12-09 12:50:50 -06:00 · 2017-12-09 12:50:50 -06:00 · 7808841390
commit 7808841390
4 changed files with 240 additions and 0 deletions
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--- a/Cargo.toml
+++ b/Cargo.toml
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+[package]
+name = "futuretest"
+version = "0.1.0"
+authors = ["Mahmoud Al-Qudsi <mqudsi@neosmart.net>"]
+
+[dependencies]
+futures = "*"
+tokio-core = "*"
--- a/src/main.rs
+++ b/src/main.rs
@ -0,0 +1,20 @@
+extern crate futures;
+extern crate tokio_core;
+use futures::future::{self};
+use futures::future::*;
+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")
+        .and_then(|_|
+             future::result(Ok(())
+                .map_err(|()| "String error".to_owned())
+            )
+        )
+    ;
+
+    core.run(f).unwrap();
+}