Missing warning for invalid recursive val.

Compiler version

3.1.1

Minimized code

val a: Int = a

https://scastie.scala-lang.org/9Naw4C8JRuKQtPd0VXBXLw

No warnings or compilation errors

Expectation

Compiler error or warning. Scala 2 gives value a in object Playground does nothing other than call itself recursively

Without warning, this is easy to create bugs like this. For eg:

 def create[F[_], S](using enc: Encoder[S])(state: S, fsm: FSM[F, S, Cmd, Option[Stat]]) =
    new Stat[F]:
      val state = state
      val fsm   = fsm

[liufengyun]

Asking the obvious, why isn’t -Ysafe-init a default?

There is still something we want to improve, in particular, better error messages for handling inner classes, and improve the modularity of the check (warn for subtle initialization behavior of open class/traits).

And we also want to get more community feedback before turning it on by default.

[mbovel]

Excellent, indeed:

28 |  val y: Int = y
   |      ^
   |      Access non-initialized value y. Calling trace:
   |       -> val y: Int = y    [ <...>.scala:28 ]

it’s still a good idea to have an additional check for such cases that are enabled by default.

Is it? Shouldn’t we encourage users interested in these checks to use -Ysafe-init instead, as it is a way more robust and powerful alternative to the shallow checks we could add by default?

@Swoorup could you use this flag for your use-cases?