fix isNew determination

Author: Christoph Bühler

src/imports/DefaultImport.ts

@@ -10,7 +10,7 @@ import { AliasedImport } from './Import';
  */
 export class DefaultImport implements AliasedImport {
     public get isNew(): boolean {
-        return this.start !== undefined && this.end !== undefined;
+        return this.start === undefined || this.end === undefined;
     }
 
     constructor(public libraryName: string, public alias: string, public start?: number, public end?: number) { }

src/imports/ExternalModuleImport.ts

@@ -10,7 +10,7 @@ import { AliasedImport } from './Import';
  */
 export class ExternalModuleImport implements AliasedImport {
     public get isNew(): boolean {
-        return this.start !== undefined && this.end !== undefined;
+        return this.start === undefined || this.end === undefined;
     }
 
     constructor(public libraryName: string, public alias: string, public start?: number, public end?: number) { }

src/imports/NamedImport.ts

@@ -14,7 +14,7 @@ export class NamedImport implements Import {
     public specifiers: SymbolSpecifier[] = [];
 
     public get isNew(): boolean {
-        return this.start !== undefined && this.end !== undefined;
+        return this.start === undefined || this.end === undefined;
     }
 
     constructor(public libraryName: string, public start?: number, public end?: number) { }

src/imports/NamespaceImport.ts

@@ -9,7 +9,7 @@ import { AliasedImport } from './Import';
  */
 export class NamespaceImport implements AliasedImport {
     public get isNew(): boolean {
-        return this.start !== undefined && this.end !== undefined;
+        return this.start === undefined || this.end === undefined;
     }
 
     constructor(public libraryName: string, public alias: string, public start?: number, public end?: number) { }

src/imports/StringImport.ts

@@ -9,7 +9,7 @@ import { Import } from './Import';
  */
 export class StringImport implements Import {
     public get isNew(): boolean {
-        return this.start !== undefined && this.end !== undefined;
+        return this.start === undefined || this.end === undefined;
     }
 
     constructor(public libraryName: string, public start?: number, public end?: number) { }