std: Change assert_eq!() to use {} instead of {:?}

Formatting via reflection has been a little questionable for some time now, and
it's a little unfortunate that one of the standard macros will silently use
reflection when you weren't expecting it. This adds small bits of code bloat to
libraries, as well as not always being necessary. In light of this information,
this commit switches assert_eq!() to using {} in the error message instead of
{:?}.

In updating existing code, there were a few error cases that I encountered:

* It's impossible to define Show for [T, ..N]. I think DST will alleviate this
  because we can define Show for [T].
* A few types here and there just needed a #[deriving(Show)]
* Type parameters needed a Show bound, I often moved this to `assert!(a == b)`
* `Path` doesn't implement `Show`, so assert_eq!() cannot be used on two paths.
  I don't think this is much of a regression though because {:?} on paths looks
  awful (it's a byte array).

Concretely speaking, this shaved 10K off a 656K binary. Not a lot, but sometime
significant for smaller binaries.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
index 4b5a05f4cb8..7b885df0317 100644
--- a/src/libsyntax/util/interner.rs
+++ b/src/libsyntax/util/interner.rs
@@ -18,6 +18,7 @@ use collections::HashMap;
 use std::cast;
 use std::cell::RefCell;
 use std::cmp::Equiv;
+use std::fmt;
 use std::hash::Hash;
 use std::rc::Rc;
 
@@ -114,6 +115,13 @@ impl Str for RcStr {
     }
 }
 
+impl fmt::Show for RcStr {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use std::fmt::Show;
+        self.as_slice().fmt(f)
+    }
+}
+
 impl RcStr {
     pub fn new(string: &str) -> RcStr {
         RcStr {