Switch to isNodeDescendantOf

Author: sandersn

src/compiler/checker.ts

@@ -4420,26 +4420,13 @@ namespace ts {
             let container = getThisContainer(node, /*includeArrowFunctions*/ false);
             let parent = container && container.parent;
             if (parent && (isClassLike(parent) || parent.kind === SyntaxKind.InterfaceDeclaration)) {
-                if (!(container.flags & NodeFlags.Static) && !isConstructorParameter(node, container)) {
+                if (!(container.flags & NodeFlags.Static) &&
+                    (container.kind !== SyntaxKind.Constructor || isNodeDescendentOf(node, (<ConstructorDeclaration>container).body))) {
                     return getDeclaredTypeOfClassOrInterface(getSymbolOfNode(parent)).thisType;
                 }
             }
             error(node, Diagnostics.A_this_type_is_available_only_in_a_non_static_member_of_a_class_or_interface);
             return unknownType;
-
-            function isConstructorParameter(node: Node, container: Node) {
-                if (container.kind === SyntaxKind.Constructor) {
-                    let ctor = (<ConstructorDeclaration>container);
-                    while (node && node !== ctor) {
-                        if (node === ctor.body) {
-                            return false;
-                        }
-                        node = node.parent;
-                    }
-
-                    return true;
-                }
-            }
         }
 
         function getTypeFromThisTypeNode(node: TypeNode): Type {

src/compiler/emitter.ts

@@ -359,14 +359,6 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
             sourceMaps: sourceMapDataList
         };
 
-        function isNodeDescendentOf(node: Node, ancestor: Node): boolean {
-            while (node) {
-                if (node === ancestor) return true;
-                node = node.parent;
-            }
-            return false;
-        }
-
         function isUniqueLocalName(name: string, container: Node): boolean {
             for (let node = container; isNodeDescendentOf(node, container); node = node.nextContainer) {
                 if (node.locals && hasProperty(node.locals, name)) {

src/compiler/utilities.ts

@@ -1151,6 +1151,14 @@ namespace ts {
         return !!node && (node.kind === SyntaxKind.ArrayBindingPattern || node.kind === SyntaxKind.ObjectBindingPattern);
     }
 
+    export function isNodeDescendentOf(node: Node, ancestor: Node): boolean {
+        while (node) {
+            if (node === ancestor) return true;
+            node = node.parent;
+        }
+        return false;
+    }
+
     export function isInAmbientContext(node: Node): boolean {
         while (node) {
             if (node.flags & (NodeFlags.Ambient | NodeFlags.DeclarationFile)) {