Singleton-type inference in method return type

According to SLS, a type in value definition(in method definition, too) is not determined by the local type inference, so

```scala
scala> val p = "hello"
p: String = hello

scala> val v = p : p.type
v: p.type = hello
```

seems ok, but

```scala
scala> def v = p : p.type
v: String
```

. Or SLS is wrong?