Lints should respect -Wmacros

[neko-kai]

reproduction steps

using Scala 2.13.3:

Scastie showing the warning: https://scastie.scala-lang.org/r3Fnc5YcSzeA91CKs06EtQ

// libraryDependencies += "com.github.alexarchambault" %% "scalacheck-shapeless_1.14" % "1.2.5"

import org.scalacheck.Arbitrary

final case class X(s: String)
object X {
  implicit val arb: Arbitrary[X] = org.scalacheck.derive.MkArbitrary[X].arbitrary
}

problem

Getting a warning:

Block result was adapted via implicit conversion (method apply) taking a by-name parameter

But the warning applies to the code generated by shapeless.Lazy macro, not user-written code. This makes it mandatory to disable the -Xlint:byname-implicit due to the massive amount of false positives whenever implicit derivation is used.

[som-snytt]

-Wunused consults -Wmacros, and it looks like -Xlint:missing-interpolator attempts to avoid reporting on macro expansion. Maybe typer could just tell reporter not to report warnings.

[SethTisue]

fyi @milessabin

[milessabin]

I'd seen this and assumed the linter rule was trigger happy and disabled it.

There's nothing I can do here because the structure is essential to the encoding of Lazy. It's a shame this wasn't picked up in the community build.

[diesalbla]

The error message was introduced by scala/scala#8590

[SethTisue]

volunteer to attempt to improve the situation?

[lrytz]

Maybe we can find a secret handshake to sidestep the warning? It would also be good not to warn if the method call is written by the user, not synthesized by the compiler:

scala> implicit def f(x: => Int): Int = x
warning: 1 feature warning; for details, enable `:setting -feature` or `:replay -feature`
def f(x: => Int): Int

scala> { println("hi"); f(1) }
                         ^
       warning: Block result was adapted via implicit conversion (method f) taking a by-name parameter
hi
val res0: Int = 1

Alternatively, the shapeless macro could add a : @nowarn("cat=lint-byname-implicit") ascription.

scala> { println("hi"); f(1) } : @annotation.nowarn("cat=lint-byname-implicit")
hi

[alexklibisz]

If anyone else is trying to figure out how to suppress just this one type of lint warning:

-Xlint:-byname-implicit