Fix #498: Optimize rest arguments

src/compiler/checker.ts

@@ -13248,6 +13248,14 @@ namespace ts {
             // or parameter. The flow container is the innermost function starting with which we analyze the control
             // flow graph to determine the control flow based type.
             const isParameter = getRootDeclaration(declaration).kind === SyntaxKind.Parameter;
+
+            if (isParameter) {
+                const parameterDeclaration = getRootDeclaration(declaration) as ParameterDeclaration;
+                if (parameterDeclaration.dotDotDotToken) {
+                    getNodeLinks(parameterDeclaration).flags |= NodeCheckFlags.EmitRestParam;
+                }
+            }
+
             const declarationContainer = getControlFlowContainer(declaration);
             let flowContainer = getControlFlowContainer(node);
             const isOuterVariable = flowContainer !== declarationContainer;

src/compiler/transformers/es2015.ts

@@ -1341,7 +1341,7 @@ namespace ts {
          *                                          synthesized call to `super`
          */
         function shouldAddRestParameter(node: ParameterDeclaration, inConstructorWithSynthesizedSuper: boolean) {
-            return node && node.dotDotDotToken && node.name.kind === SyntaxKind.Identifier && !inConstructorWithSynthesizedSuper;
+            return node && node.dotDotDotToken && node.name.kind === SyntaxKind.Identifier && !inConstructorWithSynthesizedSuper && resolver.getNodeCheckFlags(node) & NodeCheckFlags.EmitRestParam;
         }
 
         /**

src/compiler/types.ts

@@ -3313,6 +3313,7 @@ namespace ts {
         AssignmentsMarked                   = 0x00400000,  // Parameter assignments have been marked
         ClassWithConstructorReference       = 0x00800000,  // Class that contains a binding to its constructor inside of the class body.
         ConstructorReferenceInClass         = 0x01000000,  // Binding to a class constructor inside of the class's body.
+        EmitRestParam                       = 0x02000000,  // Rest parameter used in body.
     }
 
     /* @internal */

tests/baselines/reference/accessorWithRestParam.js

@@ -9,22 +9,12 @@ var C = /** @class */ (function () {
     function C() {
     }
     Object.defineProperty(C.prototype, "X", {
-        set: function () {
-            var v = [];
-            for (var _i = 0; _i < arguments.length; _i++) {
-                v[_i] = arguments[_i];
-            }
-        },
+        set: function () { },
         enumerable: true,
         configurable: true
     });
     Object.defineProperty(C, "X", {
-        set: function () {
-            var v2 = [];
-            for (var _i = 0; _i < arguments.length; _i++) {
-                v2[_i] = arguments[_i];
-            }
-        },
+        set: function () { },
         enumerable: true,
         configurable: true
     });

tests/baselines/reference/arrayLiteralInNonVarArgParameter.js

@@ -5,10 +5,5 @@ panic([], 'one', 'two');
 
 
 //// [arrayLiteralInNonVarArgParameter.js]
-function panic(val) {
-    var opt = [];
-    for (var _i = 1; _i < arguments.length; _i++) {
-        opt[_i - 1] = arguments[_i];
-    }
-}
+function panic(val) { }
 panic([], 'one', 'two');

tests/baselines/reference/assignmentCompatWithCallSignaturesWithRestParameters.js

@@ -49,49 +49,19 @@ var a4: (x?: number, y?: string, ...z: number[]) => number;
 // call signatures in derived types must have the same or fewer optional parameters as the target for assignment
 var a; // ok, same number of required params
 a = function () { return 1; }; // ok, same number of required params
-a = function () {
-    var args = [];
-    for (var _i = 0; _i < arguments.length; _i++) {
-        args[_i] = arguments[_i];
-    }
-    return 1;
-}; // ok, same number of required params
-a = function () {
-    var args = [];
-    for (var _i = 0; _i < arguments.length; _i++) {
-        args[_i] = arguments[_i];
-    }
-    return 1;
-}; // error, type mismatch
+a = function () { return 1; }; // ok, same number of required params
+a = function () { return 1; }; // error, type mismatch
 a = function (x) { return 1; }; // ok, same number of required params
 a = function (x, y, z) { return 1; }; // ok, same number of required params
 a = function (x) { return 1; }; // ok, rest param corresponds to infinite number of params
 a = function (x) { return 1; }; // error, incompatible type
 var a2;
 a2 = function () { return 1; }; // ok, fewer required params
-a2 = function () {
-    var args = [];
-    for (var _i = 0; _i < arguments.length; _i++) {
-        args[_i] = arguments[_i];
-    }
-    return 1;
-}; // ok, fewer required params
+a2 = function () { return 1; }; // ok, fewer required params
 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 _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 _i = 1; _i < arguments.length; _i++) {
-        args[_i - 1] = arguments[_i];
-    }
-    return 1;
-}; // should be type mismatch error
+a2 = function (x) { return 1; }; // ok, same number of required params
+a2 = function (x) { return 1; }; // should be type mismatch error
 a2 = function (x, y) { return 1; }; // ok, rest param corresponds to infinite number of params
 a2 = function (x, y) { return 1; }; // ok, same number of required params
 var a3;
@@ -100,24 +70,12 @@ a3 = function (x) { return 1; }; // ok, fewer required params
 a3 = function (x) { return 1; }; // ok, same number of required params
 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 _i = 1; _i < arguments.length; _i++) {
-        z[_i - 1] = arguments[_i];
-    }
-    return 1;
-}; // error
+a3 = function (x) { return 1; }; // error
 a3 = function (x, y, z) { return 1; }; // error
 var a4;
 a4 = function () { return 1; }; // ok, fewer required params
 a4 = function (x, y) { return 1; }; // error, type mismatch
 a4 = function (x) { return 1; }; // ok, all present params match
 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 _i = 1; _i < arguments.length; _i++) {
-        args[_i - 1] = arguments[_i];
-    }
-    return 1;
-}; // error, rest params have type mismatch
+a4 = function (x) { return 1; }; // error, rest params have type mismatch

tests/baselines/reference/baseTypeAfterDerivedType.js

@@ -20,11 +20,6 @@ interface Base2 {
 var Derived2 = /** @class */ (function () {
     function Derived2() {
     }
-    Derived2.prototype.method = function () {
-        var args = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            args[_i] = arguments[_i];
-        }
-    };
+    Derived2.prototype.method = function () { };
     return Derived2;
 }());

tests/baselines/reference/callWithSpread.js

@@ -70,10 +70,6 @@ var __extends = (this && this.__extends) || (function () {
     };
 })();
 function foo(x, y) {
-    var z = [];
-    for (var _i = 2; _i < arguments.length; _i++) {
-        z[_i - 2] = arguments[_i];
-    }
 }
 var a;
 var z;
@@ -108,10 +104,6 @@ var C = /** @class */ (function () {
         this.foo.apply(this, [x, y].concat(z));
     }
     C.prototype.foo = function (x, y) {
-        var z = [];
-        for (var _i = 2; _i < arguments.length; _i++) {
-            z[_i - 2] = arguments[_i];
-        }
     };
     return C;
 }());

tests/baselines/reference/checkSuperCallBeforeThisAccessing5.js

@@ -20,10 +20,6 @@ var __extends = (this && this.__extends) || (function () {
 })();
 var Based = /** @class */ (function () {
     function Based() {
-        var arg = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            arg[_i] = arguments[_i];
-        }
     }
     return Based;
 }());

tests/baselines/reference/checkSuperCallBeforeThisAccessing6.js

@@ -23,10 +23,6 @@ var __extends = (this && this.__extends) || (function () {
 })();
 var Base = /** @class */ (function () {
     function Base() {
-        var arg = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            arg[_i] = arguments[_i];
-        }
     }
     return Base;
 }());

tests/baselines/reference/checkSuperCallBeforeThisAccessing8.js

@@ -23,10 +23,6 @@ var __extends = (this && this.__extends) || (function () {
 })();
 var Base = /** @class */ (function () {
     function Base() {
-        var arg = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            arg[_i] = arguments[_i];
-        }
     }
     return Base;
 }());

tests/baselines/reference/collisionArgumentsArrowFunctions.js

@@ -18,27 +18,15 @@ var f2NoError = () => {
 
 //// [collisionArgumentsArrowFunctions.js]
 var f1 = function (i) {
-    var arguments = [];
-    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 _i = 1; _i < arguments.length; _i++) {
-        rest[_i - 1] = arguments[_i];
-    }
     var arguments = 10; // no error
 };
 var f1NoError = function (arguments) {
     var arguments = 10; // no error
 };
 var f2 = function () {
-    var restParameters = [];
-    for (var _i = 0; _i < arguments.length; _i++) {
-        restParameters[_i] = arguments[_i];
-    }
     var arguments = 10; // No Error
 };
 var f2NoError = function () {

tests/baselines/reference/collisionArgumentsClassConstructor.js

@@ -90,20 +90,12 @@ declare class c6NoError {
 // Constructors
 var c1 = /** @class */ (function () {
     function c1(i) {
-        var arguments = [];
-        for (var _i = 1; _i < arguments.length; _i++) {
-            arguments[_i - 1] = arguments[_i];
-        }
         var arguments; // no error
     }
     return c1;
 }());
 var c12 = /** @class */ (function () {
     function c12(arguments) {
-        var rest = [];
-        for (var _i = 1; _i < arguments.length; _i++) {
-            rest[_i - 1] = arguments[_i];
-        }
         var arguments = 10; // no error
     }
     return c12;
@@ -116,10 +108,6 @@ var c1NoError = /** @class */ (function () {
 }());
 var c2 = /** @class */ (function () {
     function c2() {
-        var restParameters = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            restParameters[_i] = arguments[_i];
-        }
         var arguments = 10; // no error
     }
     return c2;
@@ -132,10 +120,6 @@ var c2NoError = /** @class */ (function () {
 }());
 var c3 = /** @class */ (function () {
     function c3(arguments) {
-        var restParameters = [];
-        for (var _i = 1; _i < arguments.length; _i++) {
-            restParameters[_i - 1] = arguments[_i];
-        }
         this.arguments = arguments;
         var arguments = 10; // no error
     }
@@ -150,20 +134,12 @@ var c3NoError = /** @class */ (function () {
 }());
 var c5 = /** @class */ (function () {
     function c5(i) {
-        var arguments = [];
-        for (var _i = 1; _i < arguments.length; _i++) {
-            arguments[_i - 1] = arguments[_i];
-        }
         var arguments; // no error
     }
     return c5;
 }());
 var c52 = /** @class */ (function () {
     function c52(arguments) {
-        var rest = [];
-        for (var _i = 1; _i < arguments.length; _i++) {
-            rest[_i - 1] = arguments[_i];
-        }
         var arguments; // no error
     }
     return c52;

tests/baselines/reference/collisionArgumentsClassMethod.js

@@ -53,34 +53,18 @@ var c1 = /** @class */ (function () {
     function c1() {
     }
     c1.prototype.foo = function (i) {
-        var arguments = [];
-        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 _i = 1; _i < arguments.length; _i++) {
-            rest[_i - 1] = arguments[_i];
-        }
         var arguments = 10; // no error
     };
     c1.prototype.fooNoError = function (arguments) {
         var arguments = 10; // no error
     };
     c1.prototype.f4 = function (i) {
-        var arguments = [];
-        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 _i = 1; _i < arguments.length; _i++) {
-            rest[_i - 1] = arguments[_i];
-        }
         var arguments; // no error
     };
     c1.prototype.f4NoError = function (arguments) {
@@ -92,10 +76,6 @@ var c3 = /** @class */ (function () {
     function c3() {
     }
     c3.prototype.foo = function () {
-        var restParameters = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            restParameters[_i] = arguments[_i];
-        }
         var arguments = 10; // no error
     };
     c3.prototype.fooNoError = function () {