Fix parameter types for compareTo().

lib/src/int64.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of fixnum;
 
 /**
  * An immutable 64-bit signed integer, in the range [-2^63, 2^63 - 1].
  * Arithmetic operations may overflow in order to maintain this range.
  */
@@ skipping 440 matching lines @@
       o = new Int64(other);
     } else if (other is Int32) {
       o = other.toInt64();
     }
     if (o != null) {
       return _l == o._l && _m == o._m && _h == o._h;
     }
     return false;
   }
 
-  int compareTo(Comparable other) =>_compareTo(other);
+  int compareTo(other) => _compareTo(other);
 
   int _compareTo(other) {
     Int64 o = _promote(other);
     int signa = _h >> (_BITS2 - 1);
     int signb = o._h >> (_BITS2 - 1);
     if (signa != signb) {
       return signa == 0 ? 1 : -1;
     }
     if (_h > o._h) {
       return 1;
@@ skipping 518 matching lines @@
       if (r0 == 0 && r1 == 0 && r2 == 0) {
         return ZERO;
       } else {
         return _sub(b0, b1, b2, r0, r1, r2);
       }
     } else {
       return _negate(r0, r1, r2);
     }
   }
 }