a === b -> identical(a, b)

tests/compiler/dart2js_extra/nan_negate_test.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.
 
 // Don't convert !(a op b) to (a neg-op b) when a or b might be NaN.
 test(double n) {
   // Force known type to double, preserves NaN.
   n = 0.0 + n;
   Expect.isFalse(n >= 0);
   Expect.isTrue(!(n < 0));
 
   Expect.isFalse(n <= 0);
   Expect.isTrue(!(n > 0));
 
   Expect.isFalse(n < 0);
   Expect.isTrue(!(n >= 0));
 
   Expect.isFalse(n > 0);
   Expect.isTrue(!(n <= 0));
 
   Expect.isFalse(n == 0);
   Expect.isFalse(!(n != 0));
 
   Expect.isTrue(n != 0);
   Expect.isTrue(!(n == 0));
 
-  Expect.isFalse(n === 0);
-  Expect.isFalse(!(n !== 0));
+  Expect.isFalse(identical(n, 0));
+  Expect.isFalse(!(!identical(n, 0)));
 
-  Expect.isTrue(n !== 0);
-  Expect.isTrue(!(n === 0));
+  Expect.isTrue(!identical(n, 0));
+  Expect.isTrue(!(identical(n, 0)));
 
   Expect.isFalse(0 >= n);
   Expect.isTrue(!(0 < n));
 
   Expect.isFalse(0 <= n);
   Expect.isTrue(!(0 > n));
 
   Expect.isFalse(0 < n);
   Expect.isTrue(!(0 >= n));
 
   Expect.isFalse(0 > n);
   Expect.isTrue(!(0 <= n));
 
   Expect.isFalse(0 == n);
   Expect.isFalse(!(0 != n));
 
   Expect.isTrue(0 != n);
   Expect.isTrue(!(0 == n));
 
-  Expect.isFalse(0 === n);
-  Expect.isFalse(!(0 !== n));
+  Expect.isFalse(identical(0, n));
+  Expect.isFalse(!(!identical(0, n)));
 
-  Expect.isTrue(0 !== n);
-  Expect.isTrue(!(0 === n));
+  Expect.isTrue(!identical(0, n));
+  Expect.isTrue(!(identical(0, n)));
 }
 
 testConstant() {
   Expect.isFalse(double.NAN >= 0);
   Expect.isTrue(!(double.NAN < 0));
 
   Expect.isFalse(double.NAN <= 0);
   Expect.isTrue(!(double.NAN > 0));
 
   Expect.isFalse(double.NAN < 0);
   Expect.isTrue(!(double.NAN >= 0));
 
   Expect.isFalse(double.NAN > 0);
   Expect.isTrue(!(double.NAN <= 0));
 
   Expect.isFalse(double.NAN == 0);
   Expect.isFalse(!(double.NAN != 0));
 
   Expect.isTrue(double.NAN != 0);
   Expect.isTrue(!(double.NAN == 0));
 
-  Expect.isFalse(double.NAN === 0);
-  Expect.isFalse(!(double.NAN !== 0));
+  Expect.isFalse(identical(double.NAN, 0));
+  Expect.isFalse(!(!identical(double.NAN, 0)));
 
-  Expect.isTrue(double.NAN !== 0);
-  Expect.isTrue(!(double.NAN === 0));
+  Expect.isTrue(!identical(double.NAN, 0));
+  Expect.isTrue(!(identical(double.NAN, 0)));
 
   Expect.isFalse(0 >= double.NAN);
   Expect.isTrue(!(0 < double.NAN));
 
   Expect.isFalse(0 <= double.NAN);
   Expect.isTrue(!(0 > double.NAN));
 
   Expect.isFalse(0 < double.NAN);
   Expect.isTrue(!(0 >= double.NAN));
 
   Expect.isFalse(0 > double.NAN);
   Expect.isTrue(!(0 <= double.NAN));
 
   Expect.isFalse(0 == double.NAN);
   Expect.isFalse(!(0 != double.NAN));
 
   Expect.isTrue(0 != double.NAN);
   Expect.isTrue(!(0 == double.NAN));
 
-  Expect.isFalse(0 === double.NAN);
-  Expect.isFalse(!(0 !== double.NAN));
+  Expect.isFalse(identical(0, double.NAN));
+  Expect.isFalse(!(!identical(0, double.NAN)));
 
-  Expect.isTrue(0 !== double.NAN);
-  Expect.isTrue(!(0 === double.NAN));
+  Expect.isTrue(!identical(0, double.NAN));
+  Expect.isTrue(!(identical(0, double.NAN)));
 }
 
 main() {
   test(hideConstant(27, double.NAN));
   testConstant();
 }
 
 double hideConstant(int n, double result) {
   if (n == 1) return result;
   if ((n & 1) == 0) return hideConstant(n >> 1, result);
   return hideConstant(3 * n + 1, result);
 }