diff --git a/Jakefile b/Jakefile
index 207cfce2e7f..16330305b6a 100644
--- a/Jakefile
+++ b/Jakefile
@@ -366,7 +366,7 @@ desc("Builds the test infrastructure using the built compiler");
 task("tests", ["local", run].concat(libraryTargets));
 
 function exec(cmd, completeHandler) {
-    var ex = jake.createExec([cmd]);
+    var ex = jake.createExec([cmd], {windowsVerbatimArguments: true});
     // Add listeners for output and error
     ex.addListener("stdout", function(output) {
         process.stdout.write(output);
@@ -488,18 +488,25 @@ task("runtests-browser", ["tests", "browserify", builtLocalDirectory], function(
     exec(cmd);
 }, {async: true});
 
+function getDiffTool() {
+    var program = process.env['DIFF']
+    if (!program) {
+        fail("Add the 'DIFF' environment variable to the path of the program you want to use.")
+    }
+    return program;
+}
 
 // Baseline Diff
-desc("Diffs the compiler baselines using the diff tool specified by the %DIFF% environment variable");
+desc("Diffs the compiler baselines using the diff tool specified by the 'DIFF' environment variable");
 task('diff', function () {
-    var cmd = "%DIFF% " + refBaseline + ' ' + localBaseline;
+    var cmd = '"' +  getDiffTool()  + '" ' + refBaseline + ' ' + localBaseline;
     console.log(cmd)
     exec(cmd);
 }, {async: true});
 
-desc("Diffs the RWC baselines using the diff tool specified by the %DIFF% environment variable");
+desc("Diffs the RWC baselines using the diff tool specified by the 'DIFF' environment variable");
 task('diff-rwc', function () {
-    var cmd = "%DIFF% " + refRwcBaseline + ' ' + localRwcBaseline;
+    var cmd = '"' +  getDiffTool()  + '" ' + refRwcBaseline + ' ' + localRwcBaseline;
     console.log(cmd)
     exec(cmd);
 }, {async: true});
diff --git a/src/lib/es6.d.ts b/src/lib/es6.d.ts
index 5706924e8e3..b666b11b969 100644
--- a/src/lib/es6.d.ts
+++ b/src/lib/es6.d.ts
@@ -211,7 +211,7 @@ interface NumberConstructor {
       * Converts a string to a floating-point number. 
       * @param string A string that contains a floating-point number. 
       */
-    parseFloat(string: string);
+    parseFloat(string: string): number;
 
     /**
       * Converts A string to an integer.
@@ -438,7 +438,7 @@ interface StringConstructor {
       * @param template A well-formed template string call site representation.
       * @param substitutions A set of substitution values.
       */
-    raw(template: TemplateStringsArray, ...substitutions: any[]);
+    raw(template: TemplateStringsArray, ...substitutions: any[]): string;
 }
 
 interface IteratorResult<T> {
@@ -472,8 +472,8 @@ declare var GeneratorFunction: GeneratorFunctionConstructor;
 
 interface Generator<T> extends Iterator<T> {
     next(value?: any): IteratorResult<T>;
-    throw (exception: any);
-    return (value: T);
+    throw (exception: any): IteratorResult<T>;
+    return (value: T): IteratorResult<T>;
     // [Symbol.toStringTag]: string;
 }
 
@@ -874,7 +874,7 @@ interface DataView {
 }
 
 interface DataViewConstructor {
-    new (buffer: ArrayBuffer, byteOffset?: number, byteLength?: number);
+    new (buffer: ArrayBuffer, byteOffset?: number, byteLength?: number): DataView;
 }
 declare var DataView: DataViewConstructor;