Scala 2.13.15 marks pattern vars as unused in for comprehension if there is a filter #13041
Description
Reproduction steps
Scala version: 2.13.15
Sbt: 1.10.2
Scalac options:
ThisBuild / scalacOptions ++= List(
"-Xfatal-warnings",
"-Ywarn-unused:patvars"
) val m = Map(
"first" -> Map((true, 1), (false, 2), (true, 3)),
"second" -> Map((true, 1), (false, 2), (true, 3))
)
m.map { case (a, m1) =>
for {
(status, lag) <- m1 if status
} yield (a, status, lag)
}Problem
Getting compilation error:
[error] pattern var lag in value $anonfun is never used
[error] (status, lag) <- m1 if status
If I remove if clause, it compiles:
val m = Map(
"first" -> Map((true, 1), (false, 2), (true, 3)),
"second" -> Map((true, 1), (false, 2), (true, 3))
)
m.map { case (a, m1) =>
for {
(status, lag) <- m1
} yield (a, status, lag)
}