Fix Int64.operator == (#911)

Bug introduced in commit a4dc873, which is not released yet.

Note: `operator ==` implementations in this package are not symmetric, but we
consider that as intentional. See #910 for details.

Fixes #910.

Author: osa1

pkgs/fixnum/lib/src/int64_native.dart

@@ -270,7 +270,17 @@ class Int64 implements IntX {
   /// Returns whether this [Int64] has the same numeric value as the given
   /// object. The argument may be an [int] or an [IntX].
   @override
-  bool operator ==(Object other) => _i == _promote(other);
+  bool operator ==(Object other) {
+    if (other is Int64) {
+      return _i == other._i;
+    } else if (other is int) {
+      return _i == other;
+    } else if (other is Int32) {
+      return _i == other.toInt();
+    } else {
+      return false;
+    }
+  }
 
   @override
   Int64 abs() => Int64(_i.abs());

pkgs/fixnum/test/int32_test.dart

@@ -214,18 +214,25 @@ void main() {
     });
 
     test('==', () {
-      expect(Int32(17), isNot(equals(Int32(18))));
-      expect(Int32(17), equals(Int32(17)));
-      expect(Int32(17), isNot(equals(Int32(16))));
-      expect(Int32(17), isNot(equals(Int64(18))));
-      expect(Int32(17), equals(Int64(17)));
-      expect(Int32(17), isNot(equals(Int64(16))));
-      expect(Int32.MIN_VALUE, isNot(equals(Int32.MAX_VALUE)));
-      expect(Int32(17), isNot(equals(18)));
-      expect(Int32(17) == 17, isTrue); // ignore: unrelated_type_equality_checks
-      expect(Int32(17), isNot(equals(16)));
-      expect(Int32(17), isNot(equals(Object())));
-      expect(Int32(17), isNot(equals(null)));
+      // Note: do not use `equals` matcher below as it considers exceptions as
+      // `false`. See issue #910.
+      expect(Int32(17) == Int32(18), false);
+      expect(Int32(17) == Int32(17), true);
+      expect(Int32(17) == Int32(16), false);
+      // ignore: unrelated_type_equality_checks
+      expect(Int32(17) == Int64(18), false);
+      // ignore: unrelated_type_equality_checks
+      expect(Int32(17) == Int64(17), true);
+      // ignore: unrelated_type_equality_checks
+      expect(Int32(17) == Int64(16), false);
+      expect(Int32.MIN_VALUE == Int32.MAX_VALUE, false);
+      expect(Int32(17) == 18, false);
+      // ignore: unrelated_type_equality_checks
+      expect(Int32(17) == 17, true);
+      expect(Int32(17) == 16, false);
+      expect(Int32(17) == Object(), false);
+      // ignore: unnecessary_null_comparison
+      expect(Int32(17) == null, false);
     });
 
     test('>=', () {

pkgs/fixnum/test/int64_test.dart

@@ -459,34 +459,40 @@ void main() {
     });
 
     test('==', () {
-      expect(Int64(0), equals(Int64(0)));
-      expect(Int64(0), isNot(equals(Int64(1))));
-      expect(Int64(0), equals(Int32(0)));
-      expect(Int64(0), isNot(equals(Int32(1))));
-      expect(Int64(0) == 0, isTrue); // ignore: unrelated_type_equality_checks
-      expect(Int64(0), isNot(equals(1)));
-      expect(Int64(10), isNot(equals(Int64(11))));
-      expect(Int64(10), equals(Int64(10)));
-      expect(Int64(10), isNot(equals(Int64(9))));
-      expect(Int64(10), isNot(equals(Int32(11))));
-      expect(Int64(10), equals(Int32(10)));
-      expect(Int64(10), isNot(equals(Int32(9))));
-      expect(Int64(10), isNot(equals(11)));
-      expect(Int64(10) == 10, isTrue); // ignore: unrelated_type_equality_checks
-      expect(Int64(10), isNot(equals(9)));
-      expect(Int64(-10), equals(Int64(-10)));
+      // Note: do not use `equals` matcher below as it considers exceptions as
+      // `false`. See issue #910.
+      expect(Int64(0) == Int64(0), true);
+      expect(Int64(0) == Int64(1), false);
+      // ignore: unrelated_type_equality_checks
+      expect(Int64(0) == Int32(0), true);
+      // ignore: unrelated_type_equality_checks
+      expect(Int64(0) == Int32(1), false);
+      expect(Int64(0) == 0, true);
+      expect(Int64(0) == 1, false);
+      expect(Int64(10) == Int64(11), false);
+      expect(Int64(10) == Int64(10), true);
+      expect(Int64(10) == Int64(9), false);
+      // ignore: unrelated_type_equality_checks
+      expect(Int64(10) == Int32(11), false);
+      // ignore: unrelated_type_equality_checks
+      expect(Int64(10) == Int32(10), true);
+      // ignore: unrelated_type_equality_checks
+      expect(Int64(10) == Int32(9), false);
+      expect(Int64(10) == 11, false);
+      expect(Int64(10) == 10, true);
+      expect(Int64(10) == 9, false);
+      expect(Int64(-10) == Int64(-10), true);
       expect(Int64(-10) != Int64(-10), false);
-      expect(
-        Int64(-10) == -10,
-        isTrue,
-      ); // ignore: unrelated_type_equality_checks
-      expect(Int64(-10), isNot(equals(-9)));
-      expect(largePos, equals(largePos));
-      expect(largePos, isNot(equals(largePosPlusOne)));
-      expect(largePosPlusOne, isNot(equals(largePos)));
-      expect(Int64.MIN_VALUE, isNot(equals(Int64.MAX_VALUE)));
-      expect(Int64(17), isNot(equals(Object())));
-      expect(Int64(17), isNot(equals(null)));
+      // ignore: unrelated_type_equality_checks
+      expect(Int64(-10) == -10, true);
+      expect(Int64(-10) == -9, false);
+      expect(largePos == largePos, true);
+      expect(largePos == largePosPlusOne, false);
+      expect(largePosPlusOne == largePos, false);
+      expect(Int64.MIN_VALUE == Int64.MAX_VALUE, false);
+      expect(Int64(17) == Object(), false);
+      // ignore: unnecessary_null_comparison
+      expect(Int64(17) == null, false);
     });
 
     test('>=', () {