Fix error message when overriding with a lazy val

[smarter]

No description provided.

[anatoliykmetyuk]

It doesn't look like the test really tests the fix as it passes even without it. What we want is the -language:Scala2 flag when running the test.

sbt:dotty> repl -language:Scala2
scala> class A {
     |   val x: Int = 1
     | }
     | class B extends A {
     |   override lazy val x: Int = 2 // error
     | }
5 |  override lazy val x: Int = 2 // error
  |                    ^
  |                    may not override a non-lazy value

With the fix:

scala> class A {
     |   val x: Int = 1
     | }
     | class B extends A {
     |   override lazy val x: Int = 2 // error
     | }
5 |  override lazy val x: Int = 2 // error
  |                    ^
  |              error overriding value x in class A of type Int;
  |                lazy value x of type Int may not override a non-lazy value

Fixed.