Conditionally emit rest parameters

src/compiler/emitter.ts

@@ -243,11 +243,11 @@ module ts {
                         // }
                         // module m {
                         //     /* this is line 1 -- Assume current writer indent 8
-                        //      * line                                                --3 = 8 - 4 + 5 
+                        //      * line                                                --3 = 8 - 4 + 5
                         //            More right indented comment */                  --4 = 8 - 4 + 11
                         //     class c { }
                         // }
-                        var spacesToEmit = currentWriterIndentSpacing - firstCommentLineIndent + calculateIndent(pos, nextLineStart); 
+                        var spacesToEmit = currentWriterIndentSpacing - firstCommentLineIndent + calculateIndent(pos, nextLineStart);
                         if (spacesToEmit > 0) {
                             var numberOfSingleSpacesToEmit = spacesToEmit % getIndentSize();
                             var indentSizeSpaceString = getIndentString((spacesToEmit - numberOfSingleSpacesToEmit) / getIndentSize());
@@ -348,7 +348,7 @@ module ts {
             var emitEnd = function (node: Node) { };
 
             /** Emit the text for the given token that comes after startPos
-              * This by default writes the text provided with the given tokenKind 
+              * This by default writes the text provided with the given tokenKind
               * but if optional emitFn callback is provided the text is emitted using the callback instead of default text
               * @param tokenKind the kind of the token to search and emit
               * @param startPos the position in the source to start searching for the token
@@ -417,13 +417,13 @@ module ts {
                     // 1. Relative Column 0 based
                     sourceMapData.sourceMapMappings += base64VLQFormatEncode(lastRecordedSourceMapSpan.emittedColumn - prevEncodedEmittedColumn);
 
-                    // 2. Relative sourceIndex 
+                    // 2. Relative sourceIndex
                     sourceMapData.sourceMapMappings += base64VLQFormatEncode(lastRecordedSourceMapSpan.sourceIndex - lastEncodedSourceMapSpan.sourceIndex);
 
                     // 3. Relative sourceLine 0 based
                     sourceMapData.sourceMapMappings += base64VLQFormatEncode(lastRecordedSourceMapSpan.sourceLine - lastEncodedSourceMapSpan.sourceLine);
 
-                    // 4. Relative sourceColumn 0 based 
+                    // 4. Relative sourceColumn 0 based
                     sourceMapData.sourceMapMappings += base64VLQFormatEncode(lastRecordedSourceMapSpan.sourceColumn - lastEncodedSourceMapSpan.sourceColumn);
 
                     // 5. Relative namePosition 0 based
@@ -523,7 +523,7 @@ module ts {
 
                 function recordNewSourceFileStart(node: SourceFile) {
                     // Add the the file to tsFilePaths
-                    // If sourceroot option: Use the relative path corresponding to the common directory path 
+                    // If sourceroot option: Use the relative path corresponding to the common directory path
                     // otherwise source locations relative to map file location
                     var sourcesDirectoryPath = compilerOptions.sourceRoot ? program.getCommonSourceDirectory() : sourceMapDir;
 
@@ -625,7 +625,7 @@ module ts {
                     sourceMapDecodedMappings: []
                 };
 
-                // Normalize source root and make sure it has trailing "/" so that it can be used to combine paths with the 
+                // Normalize source root and make sure it has trailing "/" so that it can be used to combine paths with the
                 // relative paths of the sources list in the sourcemap
                 sourceMapData.sourceMapSourceRoot = ts.normalizeSlashes(sourceMapData.sourceMapSourceRoot);
                 if (sourceMapData.sourceMapSourceRoot.length && sourceMapData.sourceMapSourceRoot.charCodeAt(sourceMapData.sourceMapSourceRoot.length - 1) !== CharacterCodes.slash) {
@@ -929,15 +929,15 @@ module ts {
                     var operand = (<TypeAssertion>node.expression).operand;
 
                     // Make sure we consider all nested cast expressions, e.g.:
-                    // (<any><number><any>-A).x; 
+                    // (<any><number><any>-A).x;
                     while (operand.kind == SyntaxKind.TypeAssertion) {
                         operand = (<TypeAssertion>operand).operand;
                     }
 
                     // We have an expression of the form: (<Type>SubExpr)
                     // Emitting this as (SubExpr) is really not desirable. We would like to emit the subexpr as is.
                     // Omitting the parentheses, however, could cause change in the semantics of the generated
-                    // code if the casted expression has a lower precedence than the rest of the expression, e.g.: 
+                    // code if the casted expression has a lower precedence than the rest of the expression, e.g.:
                     //      (<any>new A).foo should be emitted as (new A).foo and not new A.foo
                     //      (<any>typeof A).toString() should be emitted as (typeof A).toString() and not typeof A.toString()
                     //      new (<any>A()) should be emitted as new (A()) and not new A()
@@ -1275,6 +1275,11 @@ module ts {
                 if (hasRestParameters(node)) {
                     var restIndex = node.parameters.length - 1;
                     var restParam = node.parameters[restIndex];
+
+                    if (!resolver.isParameterUsedInFunction(node, restParam)) {
+                        return;
+                    }
+
                     writeLine();
                     emitLeadingComments(restParam);
                     emitStart(restParam);
@@ -2156,7 +2161,7 @@ module ts {
 
                             if (commentLine >= lastCommentLine + 2) {
                                 // There was a blank line between the last comment and this comment.  This
-                                // comment is not part of the copyright comments.  Return what we have so 
+                                // comment is not part of the copyright comments.  Return what we have so
                                 // far.
                                 return detachedComments;
                             }
@@ -2335,7 +2340,7 @@ module ts {
                     }
                     // If the node is parented in the current source file we need to emit export declare or just export
                     else if (node.parent === currentSourceFile) {
-                        // If the node is exported 
+                        // If the node is exported
                         if (node.flags & NodeFlags.Export) {
                             write("export ");
                         }
@@ -2361,7 +2366,7 @@ module ts {
             }
 
             function writeImportDeclaration(node: ImportDeclaration) {
-                // note usage of writer. methods instead of aliases created, just to make sure we are using 
+                // note usage of writer. methods instead of aliases created, just to make sure we are using
                 // correct writer especially to handle asynchronous alias writing
                 emitJsDocComments(node);
                 if (node.flags & NodeFlags.Export) {
@@ -2845,7 +2850,7 @@ module ts {
                     switch (node.kind) {
                         case SyntaxKind.ConstructSignature:
                             // Interfaces cannot have return types that cannot be named
-                            diagnosticMessage = symbolAccesibilityResult.errorModuleName ? 
+                            diagnosticMessage = symbolAccesibilityResult.errorModuleName ?
                             Diagnostics.Return_type_of_constructor_signature_from_exported_interface_has_or_is_using_name_0_from_private_module_1 :
                             Diagnostics.Return_type_of_constructor_signature_from_exported_interface_has_or_is_using_private_name_0;
                             break;
@@ -3036,8 +3041,8 @@ module ts {
                 return program.getSourceFile(referenceFileName);
             }
 
-            // Contains the reference paths that needs to go in the declaration file. 
-            // Collecting this separately because reference paths need to be first thing in the declaration file 
+            // Contains the reference paths that needs to go in the declaration file.
+            // Collecting this separately because reference paths need to be first thing in the declaration file
             // and we could be collecting these paths from multiple files into single one with --out option
             var referencePathsOutput = "";
             function writeReferencePath(referencedFile: SourceFile) {
@@ -3099,7 +3104,7 @@ module ts {
                 });
             }
 
-            // TODO(shkamat): Should we not write any declaration file if any of them can produce error, 
+            // TODO(shkamat): Should we not write any declaration file if any of them can produce error,
             // or should we just not write this file like we are doing now
             if (!reportedDeclarationError) {
                 var declarationOutput = referencePathsOutput;

src/compiler/types.ts

@@ -662,6 +662,7 @@ module ts {
         shouldEmitDeclarations(): boolean;
         isDeclarationVisible(node: Declaration): boolean;
         isImplementationOfOverload(node: FunctionDeclaration): boolean;
+        isParameterUsedInFunction(func: FunctionDeclaration, param: ParameterDeclaration): boolean;
         writeTypeAtLocation(location: Node, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: TextWriter): void;
         writeReturnTypeOfSignatureDeclaration(signatureDeclaration: SignatureDeclaration, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: TextWriter): void;
         writeSymbol(symbol: Symbol, enclosingDeclaration: Node, meaning: SymbolFlags, writer: TextWriter): void;

tests/baselines/reference/arrayLiteralInNonVarArgParameter.js

@@ -6,9 +6,5 @@ panic([], 'one', 'two');
 
 //// [arrayLiteralInNonVarArgParameter.js]
 function panic(val) {
-    var opt = [];
-    for (var _i = 1; _i < arguments.length; _i++) {
-        opt[_i - 1] = arguments[_i];
-    }
 }
 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 - 0] = arguments[_i];
-    }
-    return 1;
-}; // ok, same number of required params
-a = function () {
-    var args = [];
-    for (var _i = 0; _i < arguments.length; _i++) {
-        args[_i - 0] = 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 - 0] = 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

@@ -21,10 +21,6 @@ var Derived2 = (function () {
     function Derived2() {
     }
     Derived2.prototype.method = function () {
-        var args = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            args[_i - 0] = arguments[_i];
-        }
     };
     return Derived2;
 })();

tests/baselines/reference/collisionArgumentsArrowFunctions.js

@@ -25,20 +25,12 @@ var f1 = function (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 - 0] = arguments[_i];
-    }
     var arguments = 10; // No Error
 };
 var f2NoError = function () {

tests/baselines/reference/collisionArgumentsClassConstructor.js

@@ -100,10 +100,6 @@ var c1 = (function () {
 })();
 var c12 = (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 +112,6 @@ var c1NoError = (function () {
 })();
 var c2 = (function () {
     function c2() {
-        var restParameters = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            restParameters[_i - 0] = arguments[_i];
-        }
         var arguments = 10; // no error
     }
     return c2;
@@ -132,10 +124,6 @@ var c2NoError = (function () {
 })();
 var c3 = (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
     }
@@ -160,10 +148,6 @@ var c5 = (function () {
 })();
 var c52 = (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

@@ -60,10 +60,6 @@ var c1 = (function () {
         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) {
@@ -77,10 +73,6 @@ var c1 = (function () {
         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 +84,6 @@ var c3 = (function () {
     function c3() {
     }
     c3.prototype.foo = function () {
-        var restParameters = [];
-        for (var _i = 0; _i < arguments.length; _i++) {
-            restParameters[_i - 0] = arguments[_i];
-        }
         var arguments = 10; // no error
     };
     c3.prototype.fooNoError = function () {

tests/baselines/reference/collisionArgumentsFunction.js

@@ -47,10 +47,6 @@ declare function f6(arguments: string); // no codegen no error
 //// [collisionArgumentsFunction.js]
 // Functions
 function f1(arguments) {
-    var restParameters = [];
-    for (var _i = 1; _i < arguments.length; _i++) {
-        restParameters[_i - 1] = arguments[_i];
-    }
     var arguments = 10; // no error
 }
 function f12(i) {
@@ -64,20 +60,12 @@ function f1NoError(arguments) {
     var arguments = 10; // no error
 }
 function f3() {
-    var restParameters = [];
-    for (var _i = 0; _i < arguments.length; _i++) {
-        restParameters[_i - 0] = arguments[_i];
-    }
     var arguments = 10; // no error
 }
 function f3NoError() {
     var arguments = 10; // no error
 }
 function f4(arguments) {
-    var rest = [];
-    for (var _i = 1; _i < arguments.length; _i++) {
-        rest[_i - 1] = arguments[_i];
-    }
     var arguments; // No error
 }
 function f42(i) {