Use loop instead of while(true) in libraries and compiler itself

And remove spurious fails/unreachable() calls.

src/libcore/int.rs

@@ -64,7 +64,7 @@ fn parse_buf(buf: [u8], radix: uint) -> option<int> {
         start = 1u;
     }
     let mut n = 0;
-    while true {
+    loop {
         alt char::to_digit(buf[i] as char, radix) {
           some(d) { n += (d as int) * power; }
           none { ret none; }
@@ -72,8 +72,7 @@ fn parse_buf(buf: [u8], radix: uint) -> option<int> {
         power *= radix as int;
         if i <= start { ret some(n); }
         i -= 1u;
-    }
-    fail;
+    };
 }
 
 #[doc = "Parse a string to an int"]

src/libcore/u64.rs

@@ -70,7 +70,7 @@ fn from_str(buf: str, radix: u64) -> option<u64> {
     if str::len(buf) == 0u { ret none; }
     let mut i = str::len(buf) - 1u;
     let mut power = 1u64, n = 0u64;
-    while true {
+    loop {
         alt char::to_digit(buf[i] as char, radix as uint) {
           some(d) { n += d as u64 * power; }
           none { ret none; }
@@ -78,8 +78,7 @@ fn from_str(buf: str, radix: u64) -> option<u64> {
         power *= radix;
         if i == 0u { ret some(n); }
         i -= 1u;
-    }
-    fail;
+    };
 }
 
 #[doc = "Computes the bitwise complement"]

src/libcore/uint.rs

@@ -133,7 +133,7 @@ fn parse_buf(buf: [u8], radix: uint) -> option<uint> {
     let mut i = vec::len(buf) - 1u;
     let mut power = 1u;
     let mut n = 0u;
-    while true {
+    loop {
         alt char::to_digit(buf[i] as char, radix) {
           some(d) { n += d * power; }
           none { ret none; }
@@ -141,8 +141,7 @@ fn parse_buf(buf: [u8], radix: uint) -> option<uint> {
         power *= radix;
         if i == 0u { ret some(n); }
         i -= 1u;
-    }
-    fail;
+    };
 }
 
 #[doc = "Parse a string to an int"]