Cleanup equality operator to accept any Object rather than just a SourceLocation.

lib/src/location.dart

Index: lib/src/location.dart
diff --git a/lib/src/location.dart b/lib/src/location.dart
index 41f251898c69e840aaf38199ddaf74363b3e16d2..27057424b1f3cf4ada9b14142654aabc24251c80 100644
--- a/lib/src/location.dart
+++ b/lib/src/location.dart
@@ -77,8 +77,9 @@ class SourceLocation implements Comparable<SourceLocation> {
     return offset - other.offset;
   }
 
-  bool operator ==(SourceLocation other) =>
-      sourceUrl == other.sourceUrl && offset == other.offset;
+  bool operator ==(other) =>
+      other is SourceLocation && sourceUrl == other.sourceUrl &&
+      offset == other.offset;
 
   int get hashCode => sourceUrl.hashCode + offset;