Add assertion

Author: Andy Hanson

src/compiler/utilities.ts

@@ -1861,12 +1861,12 @@ namespace ts {
     }
 
     // True if the given identifier, string literal, or number literal is the name of a declaration node
-    export function isDeclarationName(name: Node): boolean {
+    export function isDeclarationName(name: Node, parent: Node = name.parent): boolean {
         switch (name.kind) {
             case SyntaxKind.Identifier:
             case SyntaxKind.StringLiteral:
             case SyntaxKind.NumericLiteral:
-                return isDeclaration(name.parent) && name.parent.name === name;
+                return isDeclaration(parent) && parent.name === name;
             default:
                 return false;
         }
@@ -4300,7 +4300,10 @@ namespace ts {
 
     /** @internal */
     export function isNamedDeclaration(node: Node): node is NamedDeclaration & { name: DeclarationName } {
-        return !!(node as NamedDeclaration).name;
+        const name = (node as NamedDeclaration).name;
+        // Need to pass in parent as this is called from the binder before parent is set.
+        Debug.assert(!name || isDeclaration(node) && node.name === name, "A 'name' property should always be a DeclarationName.");
+        return !!name;
     }
 
     export function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName | undefined {