spurious unused warning of local given for CanEqual with -Wunused:locals and -language:strictEquality

[felher]

3.3 is awesome, thank you for bringing warnings back and all your hard work! ❤️
There seems to be a small interaction problem with what is regarded unused and -language:strictEquality though:

Compiler version

3.3.0

Minimized code

CompilerOptions:

• -language:strictEquality
• -Wunused:locals

class SomeType

def testIt(st1: SomeType, st2: SomeType): Boolean =
  given CanEqual[SomeType, SomeType] = CanEqual.derived
  st1 == st2

Output

A warning that the given definition is unused - or a compiler error that SomeType can not be compare with itself when removed

Expectation

It should not warn since the given CanEqual[...] is required by the compiler under -language:strictEquality

Scastie

https://scastie.scala-lang.org/i6Osmdc1SSK9FQlN3a65dA

[aflierl]

I would like to remark that something similar happens when using -Wunused:imports if the given is imported from somewhere else (like another package), e.g.:

object OneModule:
  import AnotherModule.given

  def meep =  Meep("meep") == Meep("moop")

final case class Meep(moop: String)

object AnotherModule:
  given CanEqual[Meep, Meep] = CanEqual.derived

Or is this / should this be another bug?

[lukestephenson]

Also observed the same issue. Created a minimal repo (before I spotted the issue was already raised) showing the compilation failure for both:

• imports of givens not working
• given within a function being reported as unused.

Thanks (agree with the earlier sentiment that 3.3 is great - thanks for the improvements!)

[joan38]

Hey! Getting hit by the same issue here but with -Wunused:imports and importing the given CanEqual.
I also have -Xfatal-warnings so it makes it impossible to make the compiler happy because either it complains that the CanEqual is missing or that the import is unused.

[joan38]

Nice! Is this targeted to be released in 3.3.2?

[Kordyjan]

Is this targeted to be released in 3.3.2?

Yes.