Improve `try!` docs to make clearer it returns `Result`.

The API documentation is not explicit enough that because `try!` returns
`Err` early for you, you can only use it in functions that return
`Result`. The book mentions this, but if you come across `try!` outside
of the book and look it up in the docs, this restriction on the return
type of the function is not particularly clear.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index e909946ece4..003c4b2b78c 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -223,7 +223,9 @@
 //! }
 //! ```
 //!
-//! `try!` is imported by the prelude, and is available everywhere.
+//! `try!` is imported by the prelude and is available everywhere, but it can only
+//! be used in functions that return `Result` because of the early return of
+//! `Err` that it provides.
 
 #![stable(feature = "rust1", since = "1.0.0")]