Add getCurrentDirectory to ServerHost

src/compiler/program.ts

@@ -187,8 +187,22 @@ namespace ts {
     const typeReferenceExtensions = [".d.ts"];
 
     function getEffectiveTypeRoots(options: CompilerOptions, host: ModuleResolutionHost) {
-        return options.typeRoots ||
-            map(defaultTypeRoots, d => combinePaths(options.configFilePath ? getDirectoryPath(options.configFilePath) : host.getCurrentDirectory(), d));
+        if (options.typeRoots) {
+            return options.typeRoots;
+        }
+
+        let currentDirectory: string;
+        if (options.configFilePath) {
+            currentDirectory = getDirectoryPath(options.configFilePath);
+        }
+        else if (host.getCurrentDirectory) {
+            currentDirectory = host.getCurrentDirectory();
+        }
+
+        if (!currentDirectory) {
+            return undefined;
+        }
+        return map(defaultTypeRoots, d => combinePaths(currentDirectory, d));
     }
 
     /**

src/server/editorServices.ts

@@ -113,6 +113,7 @@ namespace ts.server {
             this.moduleResolutionHost = {
                 fileExists: fileName => this.fileExists(fileName),
                 readFile: fileName => this.host.readFile(fileName),
+                getCurrentDirectory: () => this.host.getCurrentDirectory(),
                 directoryExists: directoryName => this.host.directoryExists(directoryName)
             };
         }

tests/cases/fourslash/server/typeReferenceOnServer.ts

@@ -0,0 +1,9 @@
+/// <reference path='../fourslash.ts' />
+
+/////// <reference types="foo" />
+////var x: number;
+////x./*1*/
+
+goTo.marker("1");
+verify.not.completionListIsEmpty();
+