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Keep unused annot on params #23037

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Merged
merged 1 commit into from
Apr 28, 2025
Merged

Keep unused annot on params #23037

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6 changes: 4 additions & 2 deletions compiler/src/dotty/tools/dotc/transform/PostTyper.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -247,8 +247,10 @@ class PostTyper extends MacroTransform with InfoTransformer { thisPhase =>
if sym.is(Param) then
registerIfUnrolledParam(sym)
// @unused is getter/setter but we want it on ordinary method params
if !sym.owner.is(Method) || sym.owner.isConstructor then
sym.keepAnnotationsCarrying(thisPhase, Set(defn.ParamMetaAnnot), orNoneOf = defn.NonBeanMetaAnnots)
// @param should be consulted only for fields
val unusing = sym.getAnnotation(defn.UnusedAnnot)
sym.keepAnnotationsCarrying(thisPhase, Set(defn.ParamMetaAnnot), orNoneOf = defn.NonBeanMetaAnnots)
unusing.foreach(sym.addAnnotation)
else if sym.is(ParamAccessor) then
// @publicInBinary is not a meta-annotation and therefore not kept by `keepAnnotationsCarrying`
val publicInBinaryAnnotOpt = sym.getAnnotation(defn.PublicInBinaryAnnot)
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13 changes: 13 additions & 0 deletions tests/warn/i23033.scala
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@@ -0,0 +1,13 @@
//> using options -Werror -Wunused:all

import scala.annotation.unused
import scala.concurrent.ExecutionContext
import scala.util.NotGiven

object Test {
given [T](using @unused ev: NotGiven[T <:< Int]): AnyRef with {}
}
object Useful:
given [T](using @unused ec: ExecutionContext): AnyRef with {}
object Syntax:
given [T] => (@unused ec: ExecutionContext) => AnyRef
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