Merge pull request #2473 from Microsoft/getSemanticDiagnosticsDeclarations

Fix issue where getSemanticDiagnostics was returning undefined on a .d.ts file.

Author: CyrusNajmabadi

src/services/services.ts

@@ -2389,7 +2389,7 @@ module ts {
 
             // If '-d' is enabled, check for emitter error. One example of emitter error is export class implements non-export interface
             let declarationDiagnostics = program.getDeclarationDiagnostics(targetSourceFile);
-            return semanticDiagnostics.concat(declarationDiagnostics);
+            return concatenate(semanticDiagnostics, declarationDiagnostics);
         }
 
         function getCompilerOptionsDiagnostics() {

tests/cases/fourslash/getSemanticDiagnosticForDeclaration1.ts

@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts" />
+
+// @declaration: true
+// @Filename: File.d.ts
+//// declare var v: string;
+
+verify.numberOfErrorsInCurrentFile(0);
+
+