Add accessible check for import usage

Author: som-snytt

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

@@ -305,8 +305,10 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
     def matchingSelector(info: ImportInfo): ImportSelector | Null =
       val qtpe = info.site
       def hasAltMember(nm: Name) = qtpe.member(nm).hasAltWith: alt =>
-           alt.symbol == sym
-        || nm.isTypeName && alt.symbol.isAliasType && alt.info.dealias.typeSymbol == sym
+        val sameSym =
+             alt.symbol == sym
+          || nm.isTypeName && alt.symbol.isAliasType && alt.info.dealias.typeSymbol == sym
+        sameSym && alt.symbol.isAccessibleFrom(qtpe)
       def loop(sels: List[ImportSelector]): ImportSelector | Null = sels match
         case sel :: sels =>
           val matches =

tests/warn/i23347.scala

@@ -0,0 +1,22 @@
+//> using options -Wunused:all
+
+object USED {
+  case class A(value: Int)
+}
+
+object UNUSED {
+  // In reality UNUSED would contain several other necessary members!
+  private type A = USED.A // warn private
+  class B
+}
+
+object Test {
+  import USED.*
+  import UNUSED.*
+
+  def foo(a: A): Int = a.value
+
+  def g(b: B) = ()
+
+}
+