librustc: Remove the fallback to int from typechecking.

This breaks a fair amount of code. The typical patterns are:

* `for _ in range(0, 10)`: change to `for _ in range(0u, 10)`;

* `println!("{}", 3)`: change to `println!("{}", 3i)`;

* `[1, 2, 3].len()`: change to `[1i, 2, 3].len()`.

RFC #30. Closes #6023.

[breaking-change]

src/libcore/ops.rs

@@ -570,11 +570,18 @@ pub trait Shl<RHS,Result> {
 
 macro_rules! shl_impl(
     ($($t:ty)*) => ($(
-        #[cfg(not(test))]
+        #[cfg(stage0)]
         impl Shl<$t, $t> for $t {
             #[inline]
             fn shl(&self, other: &$t) -> $t { (*self) << (*other) }
         }
+        #[cfg(not(stage0), not(test))]
+        impl Shl<$t, $t> for $t {
+            #[inline]
+            fn shl(&self, other: &$t) -> $t {
+                (*self) << (*other as uint)
+            }
+        }
     )*)
 )
 
@@ -612,11 +619,16 @@ pub trait Shr<RHS,Result> {
 
 macro_rules! shr_impl(
     ($($t:ty)*) => ($(
-        #[cfg(not(test))]
+        #[cfg(stage0, not(test))]
         impl Shr<$t, $t> for $t {
             #[inline]
             fn shr(&self, other: &$t) -> $t { (*self) >> (*other) }
         }
+        #[cfg(not(stage0), not(test))]
+        impl Shr<$t, $t> for $t {
+            #[inline]
+            fn shr(&self, other: &$t) -> $t { (*self) >> (*other as uint) }
+        }
     )*)
 )