No warn param of overriding method

Author: som-snytt

compiler/src/dotty/tools/dotc/transform/CheckUnused.scala

@@ -580,6 +580,7 @@ object CheckUnused:
       end checkExplicit
       // begin
       if !infos.skip(m)
+        && !m.nextOverriddenSymbol.exists
         && !allowed
       then
         checkExplicit()

tests/warn/i22742.scala

@@ -0,0 +1,10 @@
+//> using options -Wunused:all -Werror
+
+trait Foldable[F[_]]:
+  def foldLeft[A, B](fa: F[A], b: B)(f: (B, A) => B): B
+
+type Id[A] = A
+
+given foldableId: Foldable[Id] =
+  new Foldable[Id]:
+    def foldLeft[A, B](fa: Id[A], b: B)(f: (B, A) => B): B = b