Don't report errors for empty generator functions with type annotations.

Author: CyrusNajmabadi

src/compiler/checker.ts

@@ -7340,7 +7340,7 @@ module ts {
 
  function checkFunctionExpressionOrObjectLiteralMethodBody(node: FunctionExpression | MethodDeclaration) {
  Debug.assert(node.kind !== SyntaxKind.MethodDeclaration || isObjectLiteralMethod(node));
- if (node.type) {
+ if (node.type && !node.asteriskToken) {
  checkIfNonVoidFunctionHasReturnExpressionsOrSingleThrowStatment(node, getTypeFromTypeNodeOrHeritageClauseElement(node.type));
  }
 
@@ -8906,7 +8906,7 @@ module ts {
  }
 
  checkSourceElement(node.body);
- if (node.type && !isAccessor(node.kind)) {
+ if (node.type && !isAccessor(node.kind) && !node.asteriskToken) {
  checkIfNonVoidFunctionHasReturnExpressionsOrSingleThrowStatment(node, getTypeFromTypeNodeOrHeritageClauseElement(node.type));
  }