Merge pull request #8197 from Microsoft/transforms-skip-emit

Skip emit of this parameters

src/compiler/binder.ts

@@ -2267,6 +2267,11 @@ namespace ts {
             transformFlags |= TransformFlags.AssertTypeScript;
         }
 
+        // If the parameter's name is 'this', then it is TypeScript syntax.
+        if (node.name && (node.name as Identifier).originalKeywordKind === SyntaxKind.ThisKeyword) {
+            transformFlags |= TransformFlags.AssertTypeScript;
+        }
+
         // If a parameter has an accessibility modifier, then it is TypeScript syntax.
         if (hasModifier(node, ModifierFlags.AccessibilityModifier)) {
             transformFlags |= TransformFlags.AssertTypeScript | TransformFlags.ContainsParameterPropertyAssignments;

src/compiler/transformers/ts.ts

@@ -359,6 +359,7 @@ namespace ts {
                     // - accessibility modifiers
                     // - the question mark (?) token for optional parameters
                     // - type annotations
+                    // - this parameters
                     return visitParameter(<ParameterDeclaration>node);
 
                 case SyntaxKind.ParenthesizedExpression:
@@ -2120,10 +2121,14 @@ namespace ts {
          * This function will be called when one of the following conditions are met:
          * - The node has an accessibility modifier.
          * - The node has a questionToken.
+         * - The node's kind is ThisKeyword.
          *
          * @param node The parameter declaration node.
          */
         function visitParameter(node: ParameterDeclaration) {
+            if (node.name && (node.name as Identifier).originalKeywordKind === SyntaxKind.ThisKeyword) {
+                return undefined;
+            }
             const clone = getMutableClone(node);
             clone.decorators = undefined;
             clone.modifiers = undefined;

tests/baselines/reference/thisTypeInFunctionsNegative.js

@@ -341,18 +341,19 @@ var ThisConstructor = (function () {
     return ThisConstructor;
 }());
 var thisConstructorType;
-function notFirst(a, this) { return this.n; }
+function notFirst(a) { return this.n; }
 ///// parse errors /////
 function modifiers(, C) {
     if ( === void 0) {  = this; }
     return this.n;
 }
-function restParam(, C) { return this.n; }
+function restParam(C) { return this.n; }
 function optional(C) { return this.n; }
 function decorated(, C) {
     if ( === void 0) {  = this; }
     return this.n;
 }
+function initializer() { }
 new C();
 number;
 {