Inconsistent warning behaviour on initialisation: warning for class but not singelton object, AND difficult to find docs about warnings

[bjornregnell]

Compiler version

Scala 3.7.3

Minimized code

//> using scala 3.7.3
//> using options -Wall

object NoWarningProvided:
  val a = b
  val b = 42

class WarningIsProvided:
  val a = b
  val b = 42

Output

$ scala compile .
Compiling project (Scala 3.7.3, JVM (21))
[warn] ./bug.scala:10:7
[warn] Access non-initialized value b. Calling trace:
[warn] ├── class WarningIsProvided:	[ bug.scala:8 ]
[warn] │   ^
[warn] └── val a = b	[ bug.scala:9 ]
[warn]             ^
[warn]   val b = 42
[warn]       ^
Compiled project (Scala 3.7.3, JVM (21))

Expectation

Same warning also for object NoWarningProvided

[bjornregnell]

See also https://scastie.scala-lang.org/xSuVourQTwa3MjqZpNp7EQ

[som-snytt]

//> using scala 3.7.3
//> using options -Wall -Ysafe-init-global

object NoWarningProvided:
  val a = b
  val b = 42

class WarningIsProvided:
  val a = b
  val b = 42

yields

-- Warning: /home/amarki/snips/i24106.scala:10:6 -------------------------------
10 |  val b = 42
   |      ^
   |      Access non-initialized value b. Calling trace:
   |      ├── class WarningIsProvided:  [ i24106.scala:8 ]
   |      │   ^
   |      └── val a = b [ i24106.scala:9 ]
   |                  ^
-- Warning: /home/amarki/snips/i24106.scala:5:10 -------------------------------
5 |  val a = b
  |          ^
  |          Access uninitialized field value b. Calling trace:
  |          ├── object NoWarningProvided:      [ i24106.scala:4 ]
  |          │   ^
  |          └── val a = b      [ i24106.scala:5 ]
  |                      ^
2 warnings found

Maybe there is an update about the -Y version getting a promotion to -W. I agree it is very confusing. (I would prefer an imperfect warning than no warning.)

[bjornregnell]

I have difficulties finding docs about warnings:

Here is no mention of -Ysafe-init-global:

[bjornregnell]

This page is deprecated although seems to be the official one:

[bjornregnell]

Perhaps a static web page with options docs should be generated based on scala compile -Y and scala compile -W so that there is one single point of truth and the static page is always updated everytime a new compiler is released... ?

[bjornregnell]

And still quite strange that I need to look for a specific -Y option to get a warning that is not included in -Wall ...

[som-snytt]

We came close to an automated page for Scala 2. It would still be nice to have a page with a drop-down to select any version you can pick with scala-cli.

I think it was "split" because it was still a topic of research; part remained -Y because "not ready for prime time". I don't know the issues.