Compiler should not allow to define @volatile val

[WojciechMazur]

@volatile annotation only makes sense on variables. The compiler should not allow to use this annotation on immutable val field.

Compiler version

All Scala 3 versions

Minimized code

class Foo:
  @volatile val x: Int = ???

Output

No warnings

Expectation

Give the same error as Scala 2:

./main.scala:2: error: values cannot be volatile
  @volatile val x: Int = ???
                ^

[scala-center-bot]

This issue was picked for the Issue Spree No. 41 of January 16th, 2024 which takes place in 2 days. @mbovel, @AnotherMedo will be working on it. If you have any insight into the issue or guidance on how to fix it, please leave it here.

[mbovel]

We can probably check it from RefChecks.transformValDef.