Make Result::{unwrap, unwrap_err} require Show

`foo.ok().unwrap()` and `foo.err().unwrap()` are the fallbacks for types
that aren't `Show`.

Closes #13379

2 files changed, 20 insertions, 15 deletions

diff --git a/src/libstd/comm/mod.rs b/src/libstd/comm/mod.rs
index 58781c01d66..e2d7a869fbc 100644
--- a/src/libstd/comm/mod.rs
+++ b/src/libstd/comm/mod.rs
@@ -496,7 +496,7 @@ impl<T: Send> Sender<T> {
                                 // This send cannot fail because the task is
                                 // asleep (we're looking at it), so the receiver
                                 // can't go away.
-                                (*a.get()).send(t).unwrap();
+                                (*a.get()).send(t).ok().unwrap();
                                 task.wake().map(|t| t.reawaken());
                                 (a, Ok(()))
                             }
diff --git a/src/libstd/result.rs b/src/libstd/result.rs
index 8bd36127db2..9ca1443ea50 100644
--- a/src/libstd/result.rs
+++ b/src/libstd/result.rs
@@ -12,6 +12,7 @@
 
 use clone::Clone;
 use cmp::Eq;
+use std::fmt::Show;
 use iter::{Iterator, FromIterator};
 use option::{None, Option, Some};
 
@@ -174,46 +175,50 @@ impl<T, E> Result<T, E> {
         }
     }
 
-    /////////////////////////////////////////////////////////////////////////
-    // Common special cases
-    /////////////////////////////////////////////////////////////////////////
-
     /// Unwraps a result, yielding the content of an `Ok`.
-    /// Fails if the value is an `Err`.
+    /// Else it returns `optb`.
     #[inline]
-    pub fn unwrap(self) -> T {
+    pub fn unwrap_or(self, optb: T) -> T {
         match self {
             Ok(t) => t,
-            Err(_) => fail!("called `Result::unwrap()` on an `Err` value")
+            Err(_) => optb
         }
     }
 
     /// Unwraps a result, yielding the content of an `Ok`.
-    /// Else it returns `optb`.
+    /// If the value is an `Err` then it calls `op` with its value.
     #[inline]
-    pub fn unwrap_or(self, optb: T) -> T {
+    pub fn unwrap_or_handle(self, op: |E| -> T) -> T {
         match self {
             Ok(t) => t,
-            Err(_) => optb
+            Err(e) => op(e)
         }
     }
+}
 
+impl<T, E: Show> Result<T, E> {
     /// Unwraps a result, yielding the content of an `Ok`.
-    /// If the value is an `Err` then it calls `op` with its value.
+    ///
+    /// Fails if the value is an `Err`.
     #[inline]
-    pub fn unwrap_or_handle(self, op: |E| -> T) -> T {
+    pub fn unwrap(self) -> T {
         match self {
             Ok(t) => t,
-            Err(e) => op(e)
+            Err(e) =>
+                fail!("called `Result::unwrap()` on an `Err` value: {}", e)
         }
     }
+}
 
+impl<T: Show, E> Result<T, E> {
     /// Unwraps a result, yielding the content of an `Err`.
+    ///
     /// Fails if the value is an `Ok`.
     #[inline]
     pub fn unwrap_err(self) -> E {
         match self {
-            Ok(_) => fail!("called `Result::unwrap_err()` on an `Ok` value"),
+            Ok(t) =>
+                fail!("called `Result::unwrap_err()` on an `Ok` value: {}", t),
             Err(e) => e
         }
     }