diff --git a/tests/baselines/reference/arrayLiteralInNonVarArgParameter.js b/tests/baselines/reference/arrayLiteralInNonVarArgParameter.js
index f44b76f24e..57cba07d6b 100644
--- a/tests/baselines/reference/arrayLiteralInNonVarArgParameter.js
+++ b/tests/baselines/reference/arrayLiteralInNonVarArgParameter.js
@@ -7,8 +7,8 @@ panic([], 'one', 'two');
 //// [arrayLiteralInNonVarArgParameter.js]
 function panic(val) {
     var opt = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        opt[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        opt[_i - 1] = arguments[_i];
     }
 }
 panic([], 'one', 'two');
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignaturesWithRestParameters.js b/tests/baselines/reference/assignmentCompatWithCallSignaturesWithRestParameters.js
index c541114f91..f4cf5cc79e 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignaturesWithRestParameters.js
+++ b/tests/baselines/reference/assignmentCompatWithCallSignaturesWithRestParameters.js
@@ -51,15 +51,15 @@ var a; // ok, same number of required params
 a = function () { return 1; }; // ok, same number of required params
 a = function () {
     var args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i - 0] = arguments[_i];
     }
     return 1;
 }; // ok, same number of required params
 a = function () {
     var args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i - 0] = arguments[_i];
     }
     return 1;
 }; // error, type mismatch
@@ -71,8 +71,8 @@ var a2;
 a2 = function () { return 1; }; // ok, fewer required params
 a2 = function () {
     var args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i - 0] = arguments[_i];
     }
     return 1;
 }; // ok, fewer required params
@@ -80,15 +80,15 @@ a2 = function (x) { return 1; }; // ok, fewer required params
 a2 = function (x) { return 1; }; // ok, same number of required params
 a2 = function (x) {
     var args = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        args[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
     }
     return 1;
 }; // ok, same number of required params
 a2 = function (x) {
     var args = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        args[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
     }
     return 1;
 }; // should be type mismatch error
@@ -102,8 +102,8 @@ a3 = function (x, y) { return 1; }; // ok, all present params match
 a3 = function (x, y, z) { return 1; }; // error
 a3 = function (x) {
     var z = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        z[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        z[_i - 1] = arguments[_i];
     }
     return 1;
 }; // error
@@ -116,8 +116,8 @@ a4 = function (x, y) { return 1; }; // error, second param has type mismatch
 a4 = function (x, y) { return 1; }; // ok, same number of required params with matching types
 a4 = function (x) {
     var args = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        args[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
     }
     return 1;
 }; // error, rest params have type mismatch
diff --git a/tests/baselines/reference/baseTypeAfterDerivedType.js b/tests/baselines/reference/baseTypeAfterDerivedType.js
index 893e0e737b..c64239ac0c 100644
--- a/tests/baselines/reference/baseTypeAfterDerivedType.js
+++ b/tests/baselines/reference/baseTypeAfterDerivedType.js
@@ -22,8 +22,8 @@ var Derived2 = (function () {
     }
     Derived2.prototype.method = function () {
         var args = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            args[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            args[_i - 0] = arguments[_i];
         }
     };
     return Derived2;
diff --git a/tests/baselines/reference/collisionArgumentsArrowFunctions.js b/tests/baselines/reference/collisionArgumentsArrowFunctions.js
index c2f70d0ac9..0aa939e1a2 100644
--- a/tests/baselines/reference/collisionArgumentsArrowFunctions.js
+++ b/tests/baselines/reference/collisionArgumentsArrowFunctions.js
@@ -19,15 +19,15 @@ var f2NoError = () => {
 //// [collisionArgumentsArrowFunctions.js]
 var f1 = function (i) {
     var arguments = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        arguments[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        arguments[_i - 1] = arguments[_i];
     }
     var arguments; // no error
 };
 var f12 = function (arguments) {
     var rest = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        rest[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        rest[_i - 1] = arguments[_i];
     }
     var arguments = 10; // no error
 };
@@ -36,8 +36,8 @@ var f1NoError = function (arguments) {
 };
 var f2 = function () {
     var restParameters = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        restParameters[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        restParameters[_i - 0] = arguments[_i];
     }
     var arguments = 10; // No Error
 };
diff --git a/tests/baselines/reference/collisionArgumentsClassConstructor.js b/tests/baselines/reference/collisionArgumentsClassConstructor.js
index 0581b37a1e..ca743777b3 100644
--- a/tests/baselines/reference/collisionArgumentsClassConstructor.js
+++ b/tests/baselines/reference/collisionArgumentsClassConstructor.js
@@ -91,8 +91,8 @@ declare class c6NoError {
 var c1 = (function () {
     function c1(i) {
         var arguments = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            arguments[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            arguments[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     }
@@ -101,8 +101,8 @@ var c1 = (function () {
 var c12 = (function () {
     function c12(arguments) {
         var rest = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rest[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rest[_i - 1] = arguments[_i];
         }
         var arguments = 10; // no error
     }
@@ -117,8 +117,8 @@ var c1NoError = (function () {
 var c2 = (function () {
     function c2() {
         var restParameters = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            restParameters[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            restParameters[_i - 0] = arguments[_i];
         }
         var arguments = 10; // no error
     }
@@ -133,8 +133,8 @@ var c2NoError = (function () {
 var c3 = (function () {
     function c3(arguments) {
         var restParameters = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            restParameters[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            restParameters[_i - 1] = arguments[_i];
         }
         this.arguments = arguments;
         var arguments = 10; // no error
@@ -151,8 +151,8 @@ var c3NoError = (function () {
 var c5 = (function () {
     function c5(i) {
         var arguments = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            arguments[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            arguments[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     }
@@ -161,8 +161,8 @@ var c5 = (function () {
 var c52 = (function () {
     function c52(arguments) {
         var rest = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rest[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rest[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     }
diff --git a/tests/baselines/reference/collisionArgumentsClassMethod.js b/tests/baselines/reference/collisionArgumentsClassMethod.js
index 4ac6748a6b..10c9b28854 100644
--- a/tests/baselines/reference/collisionArgumentsClassMethod.js
+++ b/tests/baselines/reference/collisionArgumentsClassMethod.js
@@ -54,15 +54,15 @@ var c1 = (function () {
     }
     c1.prototype.foo = function (i) {
         var arguments = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            arguments[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            arguments[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     };
     c1.prototype.foo1 = function (arguments) {
         var rest = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rest[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rest[_i - 1] = arguments[_i];
         }
         var arguments = 10; // no error
     };
@@ -71,15 +71,15 @@ var c1 = (function () {
     };
     c1.prototype.f4 = function (i) {
         var arguments = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            arguments[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            arguments[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     };
     c1.prototype.f41 = function (arguments) {
         var rest = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rest[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rest[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     };
@@ -93,8 +93,8 @@ var c3 = (function () {
     }
     c3.prototype.foo = function () {
         var restParameters = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            restParameters[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            restParameters[_i - 0] = arguments[_i];
         }
         var arguments = 10; // no error
     };
diff --git a/tests/baselines/reference/collisionArgumentsFunction.js b/tests/baselines/reference/collisionArgumentsFunction.js
index 505127b7c9..9ce4a5ab0e 100644
--- a/tests/baselines/reference/collisionArgumentsFunction.js
+++ b/tests/baselines/reference/collisionArgumentsFunction.js
@@ -48,15 +48,15 @@ declare function f6(arguments: string); // no codegen no error
 // Functions
 function f1(arguments) {
     var restParameters = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        restParameters[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        restParameters[_i - 1] = arguments[_i];
     }
     var arguments = 10; // no error
 }
 function f12(i) {
     var arguments = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        arguments[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        arguments[_i - 1] = arguments[_i];
     }
     var arguments; // no error
 }
@@ -65,8 +65,8 @@ function f1NoError(arguments) {
 }
 function f3() {
     var restParameters = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        restParameters[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        restParameters[_i - 0] = arguments[_i];
     }
     var arguments = 10; // no error
 }
@@ -75,15 +75,15 @@ function f3NoError() {
 }
 function f4(arguments) {
     var rest = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        rest[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        rest[_i - 1] = arguments[_i];
     }
     var arguments; // No error
 }
 function f42(i) {
     var arguments = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        arguments[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        arguments[_i - 1] = arguments[_i];
     }
     var arguments; // No error
 }
diff --git a/tests/baselines/reference/collisionArgumentsFunctionExpressions.js b/tests/baselines/reference/collisionArgumentsFunctionExpressions.js
index 54039a4bce..405ceb625c 100644
--- a/tests/baselines/reference/collisionArgumentsFunctionExpressions.js
+++ b/tests/baselines/reference/collisionArgumentsFunctionExpressions.js
@@ -38,15 +38,15 @@ function foo() {
 function foo() {
     function f1(arguments) {
         var restParameters = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            restParameters[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            restParameters[_i - 1] = arguments[_i];
         }
         var arguments = 10; // no error
     }
     function f12(i) {
         var arguments = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            arguments[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            arguments[_i - 1] = arguments[_i];
         }
         var arguments; // no error
     }
@@ -55,8 +55,8 @@ function foo() {
     }
     function f3() {
         var restParameters = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            restParameters[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            restParameters[_i - 0] = arguments[_i];
         }
         var arguments = 10; // no error
     }
@@ -65,15 +65,15 @@ function foo() {
     }
     function f4(arguments) {
         var rest = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rest[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rest[_i - 1] = arguments[_i];
         }
         var arguments; // No error
     }
     function f42(i) {
         var arguments = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            arguments[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            arguments[_i - 1] = arguments[_i];
         }
         var arguments; // No error
     }
diff --git a/tests/baselines/reference/contextuallyTypingRestParameters.js b/tests/baselines/reference/contextuallyTypingRestParameters.js
index ac48cc6db0..17561f5d7f 100644
--- a/tests/baselines/reference/contextuallyTypingRestParameters.js
+++ b/tests/baselines/reference/contextuallyTypingRestParameters.js
@@ -10,8 +10,8 @@ var x: (...y: string[]) => void = function (.../*3*/y) {
 //// [contextuallyTypingRestParameters.js]
 var x = function () {
     var y = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        y[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        y[_i - 0] = arguments[_i];
     }
     var t = y;
     var x2 = t; // This should be error
diff --git a/tests/baselines/reference/declFileConstructors.js b/tests/baselines/reference/declFileConstructors.js
index 830e30e65c..327221debf 100644
--- a/tests/baselines/reference/declFileConstructors.js
+++ b/tests/baselines/reference/declFileConstructors.js
@@ -118,8 +118,8 @@ exports.ConstructorWithParameters = ConstructorWithParameters;
 var ConstructorWithRestParamters = (function () {
     function ConstructorWithRestParamters(a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     }
@@ -180,8 +180,8 @@ var GlobalConstructorWithParameters = (function () {
 var GlobalConstructorWithRestParamters = (function () {
     function GlobalConstructorWithRestParamters(a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     }
diff --git a/tests/baselines/reference/declFileFunctions.js b/tests/baselines/reference/declFileFunctions.js
index 329c61b9ab..da1917163e 100644
--- a/tests/baselines/reference/declFileFunctions.js
+++ b/tests/baselines/reference/declFileFunctions.js
@@ -78,8 +78,8 @@ function fooWithParameters(/** this is comment about a*/ a,
 exports.fooWithParameters = fooWithParameters;
 function fooWithRestParameters(a) {
     var rests = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        rests[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        rests[_i - 1] = arguments[_i];
     }
     return a + rests.join("");
 }
@@ -103,8 +103,8 @@ function nonExportedFooWithParameters(/** this is comment about a*/ a,
 }
 function nonExportedFooWithRestParameters(a) {
     var rests = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        rests[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        rests[_i - 1] = arguments[_i];
     }
     return a + rests.join("");
 }
@@ -123,8 +123,8 @@ function globalfooWithParameters(/** this is comment about a*/ a,
 }
 function globalfooWithRestParameters(a) {
     var rests = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        rests[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        rests[_i - 1] = arguments[_i];
     }
     return a + rests.join("");
 }
diff --git a/tests/baselines/reference/declFileMethods.js b/tests/baselines/reference/declFileMethods.js
index 9b0e42414e..2b82a4b71b 100644
--- a/tests/baselines/reference/declFileMethods.js
+++ b/tests/baselines/reference/declFileMethods.js
@@ -205,8 +205,8 @@ var c1 = (function () {
     };
     c1.prototype.fooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -224,8 +224,8 @@ var c1 = (function () {
     };
     c1.prototype.privateFooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -243,8 +243,8 @@ var c1 = (function () {
     };
     c1.staticFooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -262,8 +262,8 @@ var c1 = (function () {
     };
     c1.privateStaticFooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -288,8 +288,8 @@ var c2 = (function () {
     };
     c2.prototype.fooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -307,8 +307,8 @@ var c2 = (function () {
     };
     c2.prototype.privateFooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -326,8 +326,8 @@ var c2 = (function () {
     };
     c2.staticFooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
@@ -345,8 +345,8 @@ var c2 = (function () {
     };
     c2.privateStaticFooWithRestParameters = function (a) {
         var rests = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            rests[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            rests[_i - 1] = arguments[_i];
         }
         return a + rests.join("");
     };
diff --git a/tests/baselines/reference/declFileRestParametersOfFunctionAndFunctionType.js b/tests/baselines/reference/declFileRestParametersOfFunctionAndFunctionType.js
index c6d26308ab..2d071c80de 100644
--- a/tests/baselines/reference/declFileRestParametersOfFunctionAndFunctionType.js
+++ b/tests/baselines/reference/declFileRestParametersOfFunctionAndFunctionType.js
@@ -13,8 +13,8 @@ var f6 = () => { return [<any>10]; }
 //// [declFileRestParametersOfFunctionAndFunctionType.js]
 function f1() {
     var args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i - 0] = arguments[_i];
     }
 }
 function f2(x) {
diff --git a/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction1.js b/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction1.js
index 72d2545e61..2505e3f608 100644
--- a/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction1.js
+++ b/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction1.js
@@ -18,8 +18,8 @@ var TestFile = (function () {
         var _this = this;
         return function () {
             var x = [];
-            for (var _a = 0; _a < arguments.length; _a++) {
-                x[_a - 0] = arguments[_a];
+            for (var _i = 0; _i < arguments.length; _i++) {
+                x[_i - 0] = arguments[_i];
             }
             /// <summary>Test summary</summary>
             /// <param name="message" type="String" />
diff --git a/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction2.js b/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction2.js
index 3309a395ef..53f6d08eaf 100644
--- a/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction2.js
+++ b/tests/baselines/reference/detachedCommentAtStartOfLambdaFunction2.js
@@ -22,8 +22,8 @@ var TestFile = (function () {
             /// <param name="message" type="String" />
             /// <returns type="Function" />
             var x = [];
-            for (var _a = 0; _a < arguments.length; _a++) {
-                x[_a - 0] = arguments[_a];
+            for (var _i = 0; _i < arguments.length; _i++) {
+                x[_i - 0] = arguments[_i];
             }
             return message + _this.name;
         };
diff --git a/tests/baselines/reference/funcdecl.js b/tests/baselines/reference/funcdecl.js
index 32d024f4ee..de080873b9 100644
--- a/tests/baselines/reference/funcdecl.js
+++ b/tests/baselines/reference/funcdecl.js
@@ -105,8 +105,8 @@ function withOptionalInitializedParams(a, c) {
 var withOptionalInitializedParamsVar = withOptionalInitializedParams;
 function withRestParams(a) {
     var myRestParameter = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        myRestParameter[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        myRestParameter[_i - 1] = arguments[_i];
     }
     return myRestParameter;
 }
diff --git a/tests/baselines/reference/functionCall10.js b/tests/baselines/reference/functionCall10.js
index a9b5ca4788..9d5cb33a56 100644
--- a/tests/baselines/reference/functionCall10.js
+++ b/tests/baselines/reference/functionCall10.js
@@ -9,8 +9,8 @@ foo(1, 'bar');
 //// [functionCall10.js]
 function foo() {
     var a = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        a[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        a[_i - 0] = arguments[_i];
     }
 }
 ;
diff --git a/tests/baselines/reference/functionCall13.js b/tests/baselines/reference/functionCall13.js
index 6edf95fb4b..ce57f43215 100644
--- a/tests/baselines/reference/functionCall13.js
+++ b/tests/baselines/reference/functionCall13.js
@@ -10,8 +10,8 @@ foo('foo', 1, 3);
 //// [functionCall13.js]
 function foo(a) {
     var b = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        b[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        b[_i - 1] = arguments[_i];
     }
 }
 foo('foo', 1);
diff --git a/tests/baselines/reference/functionCall14.js b/tests/baselines/reference/functionCall14.js
index 343b3e58b7..47447f46db 100644
--- a/tests/baselines/reference/functionCall14.js
+++ b/tests/baselines/reference/functionCall14.js
@@ -10,8 +10,8 @@ foo('foo', 1, 3);
 //// [functionCall14.js]
 function foo(a) {
     var b = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        b[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        b[_i - 1] = arguments[_i];
     }
 }
 foo('foo', 1);
diff --git a/tests/baselines/reference/functionCall15.js b/tests/baselines/reference/functionCall15.js
index 07864c5f4c..28fa4c917c 100644
--- a/tests/baselines/reference/functionCall15.js
+++ b/tests/baselines/reference/functionCall15.js
@@ -4,7 +4,7 @@ function foo(a?:string, b?:number, ...b:number[]){}
 //// [functionCall15.js]
 function foo(a, b) {
     var b = [];
-    for (var _a = 2; _a < arguments.length; _a++) {
-        b[_a - 2] = arguments[_a];
+    for (var _i = 2; _i < arguments.length; _i++) {
+        b[_i - 2] = arguments[_i];
     }
 }
diff --git a/tests/baselines/reference/functionCall16.js b/tests/baselines/reference/functionCall16.js
index fdf7ed1542..187572a9a7 100644
--- a/tests/baselines/reference/functionCall16.js
+++ b/tests/baselines/reference/functionCall16.js
@@ -11,8 +11,8 @@ foo('foo', 'bar', 3);
 //// [functionCall16.js]
 function foo(a, b) {
     var c = [];
-    for (var _a = 2; _a < arguments.length; _a++) {
-        c[_a - 2] = arguments[_a];
+    for (var _i = 2; _i < arguments.length; _i++) {
+        c[_i - 2] = arguments[_i];
     }
 }
 foo('foo', 1);
diff --git a/tests/baselines/reference/functionCall17.js b/tests/baselines/reference/functionCall17.js
index a6794012d6..73f7fd6070 100644
--- a/tests/baselines/reference/functionCall17.js
+++ b/tests/baselines/reference/functionCall17.js
@@ -11,8 +11,8 @@ foo('foo', 'bar', 3, 4);
 //// [functionCall17.js]
 function foo(a, b, c) {
     var d = [];
-    for (var _a = 3; _a < arguments.length; _a++) {
-        d[_a - 3] = arguments[_a];
+    for (var _i = 3; _i < arguments.length; _i++) {
+        d[_i - 3] = arguments[_i];
     }
 }
 foo('foo', 1);
diff --git a/tests/baselines/reference/functionOverloadsRecursiveGenericReturnType.js b/tests/baselines/reference/functionOverloadsRecursiveGenericReturnType.js
index 73bb56b3f7..ab0baf2059 100644
--- a/tests/baselines/reference/functionOverloadsRecursiveGenericReturnType.js
+++ b/tests/baselines/reference/functionOverloadsRecursiveGenericReturnType.js
@@ -27,8 +27,8 @@ var A = (function () {
 })();
 function Choice() {
     var v_args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        v_args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        v_args[_i - 0] = arguments[_i];
     }
     return new A();
 }
diff --git a/tests/baselines/reference/genericRestArgs.js b/tests/baselines/reference/genericRestArgs.js
index 1896e886c9..75c88d7cbf 100644
--- a/tests/baselines/reference/genericRestArgs.js
+++ b/tests/baselines/reference/genericRestArgs.js
@@ -15,8 +15,8 @@ var a2Gc = makeArrayG<any[]>(1, ""); // error
 //// [genericRestArgs.js]
 function makeArrayG() {
     var items = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        items[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        items[_i - 0] = arguments[_i];
     }
     return items;
 }
diff --git a/tests/baselines/reference/implicitAnyDeclareFunctionWithoutFormalType.js b/tests/baselines/reference/implicitAnyDeclareFunctionWithoutFormalType.js
index 2d452a9f53..72d68da228 100644
--- a/tests/baselines/reference/implicitAnyDeclareFunctionWithoutFormalType.js
+++ b/tests/baselines/reference/implicitAnyDeclareFunctionWithoutFormalType.js
@@ -24,8 +24,8 @@ function func2(a, b, c) {
 ;
 function func3() {
     var args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i - 0] = arguments[_i];
     }
 }
 ;
diff --git a/tests/baselines/reference/inferTypeArgumentsInSignatureWithRestParameters.js b/tests/baselines/reference/inferTypeArgumentsInSignatureWithRestParameters.js
index 198bd3dcfa..1cc86829a6 100644
--- a/tests/baselines/reference/inferTypeArgumentsInSignatureWithRestParameters.js
+++ b/tests/baselines/reference/inferTypeArgumentsInSignatureWithRestParameters.js
@@ -14,20 +14,20 @@ i(a); // OK
 //// [inferTypeArgumentsInSignatureWithRestParameters.js]
 function f(array) {
     var args = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        args[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
     }
 }
 function g(array) {
     var args = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        args[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
     }
 }
 function h(nonarray) {
     var args = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        args[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
     }
 }
 function i(array, opt) {
diff --git a/tests/baselines/reference/inheritedConstructorWithRestParams.js b/tests/baselines/reference/inheritedConstructorWithRestParams.js
index 67b9cc0832..b924fe25db 100644
--- a/tests/baselines/reference/inheritedConstructorWithRestParams.js
+++ b/tests/baselines/reference/inheritedConstructorWithRestParams.js
@@ -24,8 +24,8 @@ var __extends = this.__extends || function (d, b) {
 var Base = (function () {
     function Base() {
         var a = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            a[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            a[_i - 0] = arguments[_i];
         }
     }
     return Base;
diff --git a/tests/baselines/reference/noImplicitAnyParametersInBareFunctions.js b/tests/baselines/reference/noImplicitAnyParametersInBareFunctions.js
index f23819244c..06848d7e89 100644
--- a/tests/baselines/reference/noImplicitAnyParametersInBareFunctions.js
+++ b/tests/baselines/reference/noImplicitAnyParametersInBareFunctions.js
@@ -63,15 +63,15 @@ function f5(x, y, z) {
 // Implicit-'any[]' error for r.
 function f6() {
     var r = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        r[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        r[_i - 0] = arguments[_i];
     }
 }
 // Implicit-'any'/'any[]' errors for x, r.
 function f7(x) {
     var r = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        r[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        r[_i - 1] = arguments[_i];
     }
 }
 function f8(x3, y3) {
@@ -87,16 +87,16 @@ var f12 = function (x, y, z) { return ""; };
 // Implicit-'any[]' error for r.
 var f13 = function () {
     var r = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        r[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        r[_i - 0] = arguments[_i];
     }
     return "";
 };
 // Implicit-'any'/'any[]' errors for x, r.
 var f14 = function (x) {
     var r = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        r[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        r[_i - 1] = arguments[_i];
     }
     return "";
 };
diff --git a/tests/baselines/reference/noImplicitAnyParametersInClass.js b/tests/baselines/reference/noImplicitAnyParametersInClass.js
index 3a2ee3e38b..82164884b8 100644
--- a/tests/baselines/reference/noImplicitAnyParametersInClass.js
+++ b/tests/baselines/reference/noImplicitAnyParametersInClass.js
@@ -106,16 +106,16 @@ var C = (function () {
         // Implicit-'any[]' error for r.
         this.pub_f13 = function () {
             var r = [];
-            for (var _a = 0; _a < arguments.length; _a++) {
-                r[_a - 0] = arguments[_a];
+            for (var _i = 0; _i < arguments.length; _i++) {
+                r[_i - 0] = arguments[_i];
             }
             return "";
         };
         // Implicit-'any'/'any[]' errors for x, r.
         this.pub_f14 = function (x) {
             var r = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                r[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                r[_i - 1] = arguments[_i];
             }
             return "";
         };
@@ -130,16 +130,16 @@ var C = (function () {
         // Implicit-'any[]' error for r.
         this.priv_f13 = function () {
             var r = [];
-            for (var _a = 0; _a < arguments.length; _a++) {
-                r[_a - 0] = arguments[_a];
+            for (var _i = 0; _i < arguments.length; _i++) {
+                r[_i - 0] = arguments[_i];
             }
             return "";
         };
         // Implicit-'any'/'any[]' errors for x, r.
         this.priv_f14 = function (x) {
             var r = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                r[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                r[_i - 1] = arguments[_i];
             }
             return "";
         };
@@ -162,15 +162,15 @@ var C = (function () {
     // Implicit-'any[]' errors for r.
     C.prototype.pub_f6 = function () {
         var r = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            r[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            r[_i - 0] = arguments[_i];
         }
     };
     // Implicit-'any'/'any[]' errors for x, r.
     C.prototype.pub_f7 = function (x) {
         var r = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            r[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            r[_i - 1] = arguments[_i];
         }
     };
     C.prototype.pub_f8 = function (x3, y3) {
@@ -194,15 +194,15 @@ var C = (function () {
     // Implicit-'any[]' errors for r.
     C.prototype.priv_f6 = function () {
         var r = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            r[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            r[_i - 0] = arguments[_i];
         }
     };
     // Implicit-'any'/'any[]' errors for x, r.
     C.prototype.priv_f7 = function (x) {
         var r = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            r[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            r[_i - 1] = arguments[_i];
         }
     };
     C.prototype.priv_f8 = function (x3, y3) {
diff --git a/tests/baselines/reference/noImplicitAnyParametersInModule.js b/tests/baselines/reference/noImplicitAnyParametersInModule.js
index b9af2af132..fccb16cefa 100644
--- a/tests/baselines/reference/noImplicitAnyParametersInModule.js
+++ b/tests/baselines/reference/noImplicitAnyParametersInModule.js
@@ -67,15 +67,15 @@ var M;
     // Implicit-'any[]' error for r.
     function m_f6() {
         var r = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            r[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            r[_i - 0] = arguments[_i];
         }
     }
     // Implicit-'any'/'any[]' errors for x and r.
     function m_f7(x) {
         var r = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            r[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            r[_i - 1] = arguments[_i];
         }
     }
     function m_f8(x3, y3) {
@@ -91,16 +91,16 @@ var M;
     // Implicit-'any[]' errors for r.
     var m_f13 = function () {
         var r = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            r[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            r[_i - 0] = arguments[_i];
         }
         return "";
     };
     // Implicit-'any'/'any[]' errors for x and r.
     var m_f14 = function (x) {
         var r = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            r[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            r[_i - 1] = arguments[_i];
         }
         return "";
     };
diff --git a/tests/baselines/reference/nonArrayRestArgs.js b/tests/baselines/reference/nonArrayRestArgs.js
index 27e05034a1..d16b7dea34 100644
--- a/tests/baselines/reference/nonArrayRestArgs.js
+++ b/tests/baselines/reference/nonArrayRestArgs.js
@@ -7,8 +7,8 @@ function foo(...rest: number) { // error
 //// [nonArrayRestArgs.js]
 function foo() {
     var rest = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        rest[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        rest[_i - 0] = arguments[_i];
     }
     var x = rest[0];
     return x;
diff --git a/tests/baselines/reference/overloadGenericFunctionWithRestArgs.js b/tests/baselines/reference/overloadGenericFunctionWithRestArgs.js
index 62676c0d03..c4b133ea44 100644
--- a/tests/baselines/reference/overloadGenericFunctionWithRestArgs.js
+++ b/tests/baselines/reference/overloadGenericFunctionWithRestArgs.js
@@ -23,8 +23,8 @@ var A = (function () {
 })();
 function Choice() {
     var v_args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        v_args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        v_args[_i - 0] = arguments[_i];
     }
     return new A();
 }
diff --git a/tests/baselines/reference/overloadResolutionOverNonCTLambdas.js b/tests/baselines/reference/overloadResolutionOverNonCTLambdas.js
index 52a2c92f10..86e84ced58 100644
--- a/tests/baselines/reference/overloadResolutionOverNonCTLambdas.js
+++ b/tests/baselines/reference/overloadResolutionOverNonCTLambdas.js
@@ -34,13 +34,13 @@ var Bugs;
     // replace(searchValue: RegExp, replaceValue: (substring: string, ...args: any[]) => string): string;
     function bug2(message) {
         var args = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            args[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            args[_i - 1] = arguments[_i];
         }
         var result = message.replace(/\{(\d+)\}/g, function (match) {
             var rest = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                rest[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                rest[_i - 1] = arguments[_i];
             }
             var index = rest[0];
             return typeof args[index] !== 'undefined' ? args[index] : match;
diff --git a/tests/baselines/reference/restArgAssignmentCompat.js b/tests/baselines/reference/restArgAssignmentCompat.js
index 5fb98a0125..a52cff7ec5 100644
--- a/tests/baselines/reference/restArgAssignmentCompat.js
+++ b/tests/baselines/reference/restArgAssignmentCompat.js
@@ -12,8 +12,8 @@ n([4], 'foo');
 //// [restArgAssignmentCompat.js]
 function f() {
     var x = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        x[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        x[_i - 0] = arguments[_i];
     }
     x.forEach(function (n, i) { return void ('item ' + i + ' = ' + n); });
 }
diff --git a/tests/baselines/reference/restParameterAssignmentCompatibility.js b/tests/baselines/reference/restParameterAssignmentCompatibility.js
index ca81a284ed..62c0204c74 100644
--- a/tests/baselines/reference/restParameterAssignmentCompatibility.js
+++ b/tests/baselines/reference/restParameterAssignmentCompatibility.js
@@ -32,8 +32,8 @@ var T = (function () {
     }
     T.prototype.m = function () {
         var p3 = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            p3[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            p3[_i - 0] = arguments[_i];
         }
     };
     return T;
diff --git a/tests/baselines/reference/restParameterNoTypeAnnotation.js b/tests/baselines/reference/restParameterNoTypeAnnotation.js
index 195b6e28a0..95e092fdd4 100644
--- a/tests/baselines/reference/restParameterNoTypeAnnotation.js
+++ b/tests/baselines/reference/restParameterNoTypeAnnotation.js
@@ -8,8 +8,8 @@ function foo(...rest) {
 //// [restParameterNoTypeAnnotation.js]
 function foo() {
     var rest = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        rest[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        rest[_i - 0] = arguments[_i];
     }
     var x = rest[0];
     return x;
diff --git a/tests/baselines/reference/restParameters.js b/tests/baselines/reference/restParameters.js
index 5b5717b34f..2e5b7bb4c9 100644
--- a/tests/baselines/reference/restParameters.js
+++ b/tests/baselines/reference/restParameters.js
@@ -10,25 +10,25 @@ function f21(a:string, b?:string, c?:number, ...d:number[]){}
 //// [restParameters.js]
 function f18(a) {
     var b = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        b[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        b[_i - 1] = arguments[_i];
     }
 }
 function f19(a, b) {
     var c = [];
-    for (var _a = 2; _a < arguments.length; _a++) {
-        c[_a - 2] = arguments[_a];
+    for (var _i = 2; _i < arguments.length; _i++) {
+        c[_i - 2] = arguments[_i];
     }
 }
 function f20(a, b) {
     var c = [];
-    for (var _a = 2; _a < arguments.length; _a++) {
-        c[_a - 2] = arguments[_a];
+    for (var _i = 2; _i < arguments.length; _i++) {
+        c[_i - 2] = arguments[_i];
     }
 }
 function f21(a, b, c) {
     var d = [];
-    for (var _a = 3; _a < arguments.length; _a++) {
-        d[_a - 3] = arguments[_a];
+    for (var _i = 3; _i < arguments.length; _i++) {
+        d[_i - 3] = arguments[_i];
     }
 }
diff --git a/tests/baselines/reference/restParamsWithNonRestParams.js b/tests/baselines/reference/restParamsWithNonRestParams.js
index 745c91d4a0..6b0caa7239 100644
--- a/tests/baselines/reference/restParamsWithNonRestParams.js
+++ b/tests/baselines/reference/restParamsWithNonRestParams.js
@@ -9,22 +9,22 @@ foo3(); // error but shouldn't be
 //// [restParamsWithNonRestParams.js]
 function foo() {
     var b = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        b[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        b[_i - 0] = arguments[_i];
     }
 }
 foo(); // ok
 function foo2(a) {
     var b = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        b[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        b[_i - 1] = arguments[_i];
     }
 }
 foo2(); // should be an error
 function foo3(a) {
     var b = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        b[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        b[_i - 1] = arguments[_i];
     }
 }
 foo3(); // error but shouldn't be
diff --git a/tests/baselines/reference/sourceMapSample.js b/tests/baselines/reference/sourceMapSample.js
index 62ad950935..96c78c94c0 100644
--- a/tests/baselines/reference/sourceMapSample.js
+++ b/tests/baselines/reference/sourceMapSample.js
@@ -57,8 +57,8 @@ var Foo;
         var str = greeter.greet();
         function foo2(greeting) {
             var restGreetings = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                restGreetings[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                restGreetings[_i - 1] = arguments[_i];
             }
             var greeters = [];
             greeters[0] = new Greeter(greeting);
diff --git a/tests/baselines/reference/sourceMapSample.sourcemap.txt b/tests/baselines/reference/sourceMapSample.sourcemap.txt
index 7608a68193..218dfb1c15 100644
--- a/tests/baselines/reference/sourceMapSample.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapSample.sourcemap.txt
@@ -454,7 +454,7 @@ sourceFile:sourceMapSample.ts
 1->Emitted(21, 13) Source(21, 37) + SourceIndex(0) name (Foo.Bar.foo2)
 2 >Emitted(21, 36) Source(21, 63) + SourceIndex(0) name (Foo.Bar.foo2)
 ---
->>>            for (var _a = 1; _a < arguments.length; _a++) {
+>>>            for (var _i = 1; _i < arguments.length; _i++) {
 1->^^^^^^^^^^^^^^^^^
 2 >                 ^^^^^^^^^^^
 3 >                            ^
@@ -474,7 +474,7 @@ sourceFile:sourceMapSample.ts
 5 >Emitted(22, 53) Source(21, 37) + SourceIndex(0) name (Foo.Bar.foo2)
 6 >Emitted(22, 57) Source(21, 63) + SourceIndex(0) name (Foo.Bar.foo2)
 ---
->>>                restGreetings[_a - 1] = arguments[_a];
+>>>                restGreetings[_i - 1] = arguments[_i];
 1 >^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 1 >
diff --git a/tests/baselines/reference/sourceMapValidationClass.js b/tests/baselines/reference/sourceMapValidationClass.js
index bc526bc674..eef5a723eb 100644
--- a/tests/baselines/reference/sourceMapValidationClass.js
+++ b/tests/baselines/reference/sourceMapValidationClass.js
@@ -22,8 +22,8 @@ class Greeter {
 var Greeter = (function () {
     function Greeter(greeting) {
         var b = [];
-        for (var _a = 1; _a < arguments.length; _a++) {
-            b[_a - 1] = arguments[_a];
+        for (var _i = 1; _i < arguments.length; _i++) {
+            b[_i - 1] = arguments[_i];
         }
         this.greeting = greeting;
         this.x1 = 10;
diff --git a/tests/baselines/reference/sourceMapValidationClass.sourcemap.txt b/tests/baselines/reference/sourceMapValidationClass.sourcemap.txt
index 8909f29310..1c80abde32 100644
--- a/tests/baselines/reference/sourceMapValidationClass.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapValidationClass.sourcemap.txt
@@ -48,7 +48,7 @@ sourceFile:sourceMapValidationClass.ts
 1 >Emitted(3, 9) Source(2, 42) + SourceIndex(0) name (Greeter.constructor)
 2 >Emitted(3, 20) Source(2, 56) + SourceIndex(0) name (Greeter.constructor)
 ---
->>>        for (var _a = 1; _a < arguments.length; _a++) {
+>>>        for (var _i = 1; _i < arguments.length; _i++) {
 1->^^^^^^^^^^^^^
 2 >             ^^^^^^^^^^^
 3 >                        ^
@@ -68,7 +68,7 @@ sourceFile:sourceMapValidationClass.ts
 5 >Emitted(4, 49) Source(2, 42) + SourceIndex(0) name (Greeter.constructor)
 6 >Emitted(4, 53) Source(2, 56) + SourceIndex(0) name (Greeter.constructor)
 ---
->>>            b[_a - 1] = arguments[_a];
+>>>            b[_i - 1] = arguments[_i];
 1 >^^^^^^^^^^^^
 2 >            ^^^^^^^^^^^^^^^^^^^^^^^^^^
 1 >
diff --git a/tests/baselines/reference/sourceMapValidationClasses.js b/tests/baselines/reference/sourceMapValidationClasses.js
index 0ab0d1e10a..96724f7c3c 100644
--- a/tests/baselines/reference/sourceMapValidationClasses.js
+++ b/tests/baselines/reference/sourceMapValidationClasses.js
@@ -58,8 +58,8 @@ var Foo;
         var str = greeter.greet();
         function foo2(greeting) {
             var restGreetings = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                restGreetings[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                restGreetings[_i - 1] = arguments[_i];
             }
             var greeters = []; /* inline block comment */
             greeters[0] = new Greeter(greeting);
diff --git a/tests/baselines/reference/sourceMapValidationClasses.sourcemap.txt b/tests/baselines/reference/sourceMapValidationClasses.sourcemap.txt
index 31d276c68a..d82ac6c3e0 100644
--- a/tests/baselines/reference/sourceMapValidationClasses.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapValidationClasses.sourcemap.txt
@@ -456,7 +456,7 @@ sourceFile:sourceMapValidationClasses.ts
 1->Emitted(21, 13) Source(21, 37) + SourceIndex(0) name (Foo.Bar.foo2)
 2 >Emitted(21, 36) Source(21, 83) + SourceIndex(0) name (Foo.Bar.foo2)
 ---
->>>            for (var _a = 1; _a < arguments.length; _a++) {
+>>>            for (var _i = 1; _i < arguments.length; _i++) {
 1->^^^^^^^^^^^^^^^^^
 2 >                 ^^^^^^^^^^^
 3 >                            ^
@@ -476,7 +476,7 @@ sourceFile:sourceMapValidationClasses.ts
 5 >Emitted(22, 53) Source(21, 37) + SourceIndex(0) name (Foo.Bar.foo2)
 6 >Emitted(22, 57) Source(21, 83) + SourceIndex(0) name (Foo.Bar.foo2)
 ---
->>>                restGreetings[_a - 1] = arguments[_a];
+>>>                restGreetings[_i - 1] = arguments[_i];
 1 >^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 1 >
diff --git a/tests/baselines/reference/sourceMapValidationFunctions.js b/tests/baselines/reference/sourceMapValidationFunctions.js
index 11b3fe40a6..58222aa48c 100644
--- a/tests/baselines/reference/sourceMapValidationFunctions.js
+++ b/tests/baselines/reference/sourceMapValidationFunctions.js
@@ -22,8 +22,8 @@ function greet(greeting) {
 function greet2(greeting, n, x) {
     if (n === void 0) { n = 10; }
     var restParams = [];
-    for (var _a = 3; _a < arguments.length; _a++) {
-        restParams[_a - 3] = arguments[_a];
+    for (var _i = 3; _i < arguments.length; _i++) {
+        restParams[_i - 3] = arguments[_i];
     }
     greetings++;
     return greetings;
@@ -31,8 +31,8 @@ function greet2(greeting, n, x) {
 function foo(greeting, n, x) {
     if (n === void 0) { n = 10; }
     var restParams = [];
-    for (var _a = 3; _a < arguments.length; _a++) {
-        restParams[_a - 3] = arguments[_a];
+    for (var _i = 3; _i < arguments.length; _i++) {
+        restParams[_i - 3] = arguments[_i];
     }
     return;
 }
diff --git a/tests/baselines/reference/sourceMapValidationFunctions.sourcemap.txt b/tests/baselines/reference/sourceMapValidationFunctions.sourcemap.txt
index a1dff1a3b9..a9e43e404a 100644
--- a/tests/baselines/reference/sourceMapValidationFunctions.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapValidationFunctions.sourcemap.txt
@@ -145,7 +145,7 @@ sourceFile:sourceMapValidationFunctions.ts
 1 >Emitted(8, 5) Source(6, 55) + SourceIndex(0) name (greet2)
 2 >Emitted(8, 25) Source(6, 78) + SourceIndex(0) name (greet2)
 ---
->>>    for (var _a = 3; _a < arguments.length; _a++) {
+>>>    for (var _i = 3; _i < arguments.length; _i++) {
 1->^^^^^^^^^
 2 >         ^^^^^^^^^^^
 3 >                    ^
@@ -165,7 +165,7 @@ sourceFile:sourceMapValidationFunctions.ts
 5 >Emitted(9, 45) Source(6, 55) + SourceIndex(0) name (greet2)
 6 >Emitted(9, 49) Source(6, 78) + SourceIndex(0) name (greet2)
 ---
->>>        restParams[_a - 3] = arguments[_a];
+>>>        restParams[_i - 3] = arguments[_i];
 1 >^^^^^^^^
 2 >        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 1 >
@@ -272,7 +272,7 @@ sourceFile:sourceMapValidationFunctions.ts
 1 >Emitted(17, 5) Source(10, 52) + SourceIndex(0) name (foo)
 2 >Emitted(17, 25) Source(10, 75) + SourceIndex(0) name (foo)
 ---
->>>    for (var _a = 3; _a < arguments.length; _a++) {
+>>>    for (var _i = 3; _i < arguments.length; _i++) {
 1->^^^^^^^^^
 2 >         ^^^^^^^^^^^
 3 >                    ^
@@ -292,7 +292,7 @@ sourceFile:sourceMapValidationFunctions.ts
 5 >Emitted(18, 45) Source(10, 52) + SourceIndex(0) name (foo)
 6 >Emitted(18, 49) Source(10, 75) + SourceIndex(0) name (foo)
 ---
->>>        restParams[_a - 3] = arguments[_a];
+>>>        restParams[_i - 3] = arguments[_i];
 1 >^^^^^^^^
 2 >        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 1 >
diff --git a/tests/baselines/reference/strictMode5.js b/tests/baselines/reference/strictMode5.js
index 747c84f554..c46de926db 100644
--- a/tests/baselines/reference/strictMode5.js
+++ b/tests/baselines/reference/strictMode5.js
@@ -22,8 +22,8 @@ function bar(x: number = 10) {
 function foo() {
     "use strict";
     var args = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        args[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i - 0] = arguments[_i];
     }
 }
 var A = (function () {
diff --git a/tests/baselines/reference/stringLiteralTypeIsSubtypeOfString.js b/tests/baselines/reference/stringLiteralTypeIsSubtypeOfString.js
index 9ba7e17b2e..37aa59bef4 100644
--- a/tests/baselines/reference/stringLiteralTypeIsSubtypeOfString.js
+++ b/tests/baselines/reference/stringLiteralTypeIsSubtypeOfString.js
@@ -133,8 +133,8 @@ var C = (function () {
     };
     C.prototype.concat = function () {
         var strings = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            strings[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            strings[_i - 0] = arguments[_i];
         }
         return null;
     };
diff --git a/tests/baselines/reference/subtypingWithCallSignatures2.js b/tests/baselines/reference/subtypingWithCallSignatures2.js
index f863756e60..a887c52d2a 100644
--- a/tests/baselines/reference/subtypingWithCallSignatures2.js
+++ b/tests/baselines/reference/subtypingWithCallSignatures2.js
@@ -254,15 +254,15 @@ var r9a = [r9arg1, r9arg2];
 var r9b = [r9arg2, r9arg1];
 var r10arg1 = function () {
     var x = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        x[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        x[_i - 0] = arguments[_i];
     }
     return x[0];
 };
 var r10arg2 = function () {
     var x = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        x[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        x[_i - 0] = arguments[_i];
     }
     return null;
 };
diff --git a/tests/baselines/reference/subtypingWithCallSignatures3.js b/tests/baselines/reference/subtypingWithCallSignatures3.js
index 936c6550bc..fb7b0fef55 100644
--- a/tests/baselines/reference/subtypingWithCallSignatures3.js
+++ b/tests/baselines/reference/subtypingWithCallSignatures3.js
@@ -170,15 +170,15 @@ var Errors;
     var r3b = [r3arg, r3arg2];
     var r4arg = function () {
         var x = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            x[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            x[_i - 0] = arguments[_i];
         }
         return null;
     };
     var r4arg2 = function () {
         var x = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            x[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            x[_i - 0] = arguments[_i];
         }
         return null;
     };
diff --git a/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution1_ES6.js b/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution1_ES6.js
index 2c53b71301..a2a96168fd 100644
--- a/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution1_ES6.js
+++ b/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution1_ES6.js
@@ -25,8 +25,8 @@ var z = foo `${1}${2}${3}`;  // any (with error)
 //// [taggedTemplateStringsWithOverloadResolution1_ES6.js]
 function foo() {
     var stuff = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        stuff[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        stuff[_i - 0] = arguments[_i];
     }
     return undefined;
 }
diff --git a/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution2_ES6.js b/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution2_ES6.js
index 1f3762e533..44da93f804 100644
--- a/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution2_ES6.js
+++ b/tests/baselines/reference/taggedTemplateStringsWithOverloadResolution2_ES6.js
@@ -20,8 +20,8 @@ var d = foo2([], 1);          // number
 //// [taggedTemplateStringsWithOverloadResolution2_ES6.js]
 function foo1() {
     var stuff = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        stuff[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        stuff[_i - 0] = arguments[_i];
     }
     return undefined;
 }
@@ -29,8 +29,8 @@ var a = foo1 `${1}`; // string
 var b = foo1([], 1); // number
 function foo2() {
     var stuff = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        stuff[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        stuff[_i - 0] = arguments[_i];
     }
     return undefined;
 }
diff --git a/tests/baselines/reference/undeclaredModuleError.js b/tests/baselines/reference/undeclaredModuleError.js
index 6814170851..e7e9b70ee7 100644
--- a/tests/baselines/reference/undeclaredModuleError.js
+++ b/tests/baselines/reference/undeclaredModuleError.js
@@ -21,8 +21,8 @@ define(["require", "exports", 'fs'], function (require, exports, fs) {
     }
     function join() {
         var paths = [];
-        for (var _a = 0; _a < arguments.length; _a++) {
-            paths[_a - 0] = arguments[_a];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            paths[_i - 0] = arguments[_i];
         }
     }
     function instrumentFile(covFileDir, covFileName, originalFilePath) {
diff --git a/tests/baselines/reference/underscoreTest1.js b/tests/baselines/reference/underscoreTest1.js
index 0c792f981a..290e7aa6c8 100644
--- a/tests/baselines/reference/underscoreTest1.js
+++ b/tests/baselines/reference/underscoreTest1.js
@@ -985,8 +985,8 @@ var fibonacci = _.memoize(function (n) {
 });
 var log = _.bind(function (message) {
     var rest = [];
-    for (var _a = 1; _a < arguments.length; _a++) {
-        rest[_a - 1] = arguments[_a];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        rest[_i - 1] = arguments[_i];
     }
 }, Date);
 _.delay(log, 1000, 'logged later');
diff --git a/tests/baselines/reference/varArgParamTypeCheck.js b/tests/baselines/reference/varArgParamTypeCheck.js
index 761e0d5ee5..c2a3341643 100644
--- a/tests/baselines/reference/varArgParamTypeCheck.js
+++ b/tests/baselines/reference/varArgParamTypeCheck.js
@@ -24,8 +24,8 @@ sequence(
 //// [varArgParamTypeCheck.js]
 function sequence() {
     var sequences = [];
-    for (var _a = 0; _a < arguments.length; _a++) {
-        sequences[_a - 0] = arguments[_a];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        sequences[_i - 0] = arguments[_i];
     }
 }
 function callback(clb) {
diff --git a/tests/baselines/reference/vararg.js b/tests/baselines/reference/vararg.js
index 0a5e23e2fa..038afb90cb 100644
--- a/tests/baselines/reference/vararg.js
+++ b/tests/baselines/reference/vararg.js
@@ -46,8 +46,8 @@ var M;
         }
         C.prototype.f = function (x) {
             var rest = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                rest[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                rest[_i - 1] = arguments[_i];
             }
             var sum = 0;
             for (var i = 0; i < rest.length; i++) {
@@ -58,14 +58,14 @@ var M;
         };
         C.prototype.fnope = function (x) {
             var rest = [];
-            for (var _a = 1; _a < arguments.length; _a++) {
-                rest[_a - 1] = arguments[_a];
+            for (var _i = 1; _i < arguments.length; _i++) {
+                rest[_i - 1] = arguments[_i];
             }
         };
         C.prototype.fonly = function () {
             var rest = [];
-            for (var _a = 0; _a < arguments.length; _a++) {
-                rest[_a - 0] = arguments[_a];
+            for (var _i = 0; _i < arguments.length; _i++) {
+                rest[_i - 0] = arguments[_i];
             }
             builder = "";
             for (var i = 0; i < rest.length; i++) {