Don't construct unnecessarily asymmetricEqualityTesterArgCompatShims

This speeds up MatchersUtil#equals by about 6-7x.

lib/jasmine-core/jasmine.js

@@ -279,7 +279,7 @@ getJasmineRequireObj().base = function(j$, jasmineGlobal) {
   };
 
   j$.isAsymmetricEqualityTester_ = function(obj) {
-    return obj && j$.isA_('Function', obj.asymmetricMatch);
+    return obj ? j$.isA_('Function', obj.asymmetricMatch) : false;
   };
 
   j$.getType_ = function(value) {
@@ -4494,13 +4494,15 @@ getJasmineRequireObj().MatchersUtil = function(j$) {
   MatchersUtil.prototype.asymmetricMatch_ = function(a, b, aStack, bStack, customTesters, diffBuilder) {
     var asymmetricA = j$.isAsymmetricEqualityTester_(a),
         asymmetricB = j$.isAsymmetricEqualityTester_(b),
-        shim = j$.asymmetricEqualityTesterArgCompatShim(this, customTesters),
+        shim,
         result;
 
-    if (asymmetricA && asymmetricB) {
+    if (asymmetricA === asymmetricB) {
       return undefined;
     }
 
+    shim = j$.asymmetricEqualityTesterArgCompatShim(this, customTesters);
+
     if (asymmetricA) {
       result = a.asymmetricMatch(b, shim);
       if (!result) {

spec/core/baseSpec.js

@@ -30,4 +30,25 @@ describe('base helpers', function() {
       }, 100);
     });
   });
+
+  describe('isAsymmetricEqualityTester_', function() {
+    it('returns false when the argument is falsy', function() {
+      expect(jasmineUnderTest.isAsymmetricEqualityTester_(null)).toBe(false);
+    });
+
+    it('returns false when the argument does not have a asymmetricMatch property', function() {
+      var obj = {};
+      expect(jasmineUnderTest.isAsymmetricEqualityTester_(obj)).toBe(false);
+    });
+
+    it("returns false when the argument's asymmetricMatch is not a function", function() {
+      var obj = { asymmetricMatch: 'yes' };
+      expect(jasmineUnderTest.isAsymmetricEqualityTester_(obj)).toBe(false);
+    });
+
+    it("returns true when the argument's asymmetricMatch is a function", function() {
+      var obj = { asymmetricMatch: function() {} };
+      expect(jasmineUnderTest.isAsymmetricEqualityTester_(obj)).toBe(true);
+    });
+  });
 });

src/core/base.js

@@ -112,7 +112,7 @@ getJasmineRequireObj().base = function(j$, jasmineGlobal) {
   };
 
   j$.isAsymmetricEqualityTester_ = function(obj) {
-    return obj && j$.isA_('Function', obj.asymmetricMatch);
+    return obj ? j$.isA_('Function', obj.asymmetricMatch) : false;
   };
 
   j$.getType_ = function(value) {

src/core/matchers/matchersUtil.js

@@ -90,13 +90,15 @@ getJasmineRequireObj().MatchersUtil = function(j$) {
   MatchersUtil.prototype.asymmetricMatch_ = function(a, b, aStack, bStack, customTesters, diffBuilder) {
     var asymmetricA = j$.isAsymmetricEqualityTester_(a),
         asymmetricB = j$.isAsymmetricEqualityTester_(b),
-        shim = j$.asymmetricEqualityTesterArgCompatShim(this, customTesters),
+        shim,
         result;
 
-    if (asymmetricA && asymmetricB) {
+    if (asymmetricA === asymmetricB) {
       return undefined;
     }
 
+    shim = j$.asymmetricEqualityTesterArgCompatShim(this, customTesters);
+
     if (asymmetricA) {
       result = a.asymmetricMatch(b, shim);
       if (!result) {