Add generator tests.

src/Workspaces/CSharpTest/CodeGeneration/SyntaxGeneratorTests.cs

@@ -530,6 +530,13 @@ public void TestReturnStatements()
             VerifySyntax<ReturnStatementSyntax>(Generator.ReturnStatement(Generator.IdentifierName("x")), "return x;");
         }
 
+        [Fact]
+        public void TestYieldReturnStatements()
+        {
+            VerifySyntax<YieldStatementSyntax>(Generator.YieldReturnStatement(Generator.LiteralExpression(1)), "yield return 1;");
+            VerifySyntax<YieldStatementSyntax>(Generator.YieldReturnStatement(Generator.IdentifierName("x")), "yield return x;");
+        }
+
         [Fact]
         public void TestThrowStatements()
         {

src/Workspaces/Core/Portable/Editing/SyntaxGenerator.cs

@@ -1399,7 +1399,7 @@ protected static SyntaxList<TNode> RemoveRange<TNode>(SyntaxList<TNode> list, in
         /// <summary>
         /// Creates a statement that can be used to yield a value from an iterator method.
         /// </summary>
-        /// <param name="expression">An optional expression that can be returned.</param>
+        /// <param name="expression">An expression that can be yielded.</param>
         internal abstract SyntaxNode YieldReturnStatement(SyntaxNode expression);
 
         /// <summary>

src/Workspaces/VisualBasicTest/CodeGeneration/SyntaxGeneratorTests.vb

@@ -475,6 +475,12 @@ End Class
             VerifySyntax(Of ReturnStatementSyntax)(Generator.ReturnStatement(Generator.IdentifierName("x")), "Return x")
         End Sub
 
+        <Fact>
+        Public Sub TestYieldReturnStatements()
+            VerifySyntax(Of YieldStatementSyntax)(Generator.YieldReturnStatement(Generator.LiteralExpression(1)), "Yield 1")
+            VerifySyntax(Of YieldStatementSyntax)(Generator.ReturnStatement(Generator.IdentifierName("x")), "Yield x")
+        End Sub
+
         <Fact>
         Public Sub TestThrowStatements()
             VerifySyntax(Of ThrowStatementSyntax)(Generator.ThrowStatement(), "Throw")