Discover inner classes for sealed hierarchy

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -15,12 +15,11 @@ package tools.nsc
 package typechecker
 
 import scala.annotation.{tailrec, unused}
-import scala.collection.mutable
+import scala.collection.mutable, mutable.ListBuffer
 import scala.reflect.internal.{Chars, TypesStats}
 import scala.reflect.internal.util.{FreshNameCreator, ListOfNil, Statistics, StringContextStripMarginOps}
 import scala.tools.nsc.Reporting.{MessageFilter, Suppression, WConf, WarningCategory}
 import scala.util.chaining._
-import mutable.ListBuffer
 import symtab.Flags._
 import Mode._
 
@@ -2653,18 +2652,29 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
       val selectorTp = packCaptured(selector1.tpe.widen).skolemizeExistential(context.owner, selector)
       val casesTyped = typedCases(cases, selectorTp, pt)
 
-      def initChildren(sym: Symbol): Unit = if (sym.isJava && sym.isSealed) {
-        sym.attachments.get[PermittedSubclassSymbols].foreach(_.permits.foreach { child =>
-          child.initialize
-          initChildren(child)
-        })
-        patmat.javaClassesByUnit.get(sym.pos.source).foreach(_.foreach { c =>
-          if (c.parentSymbols.contains(sym)) {
-            c.initialize
-            initChildren(c)
+      def initChildren(sym: Symbol): Unit =
+        if (sym.isJava && sym.isSealed)
+          sym.attachments.get[PermittedSubclassSymbols] match {
+            case Some(PermittedSubclassSymbols(permits)) =>
+              for (child <- permits if child.isJava)
+                initChildren(child.initialize)
+            case _ =>
+              val seen = mutable.HashSet.empty[Symbol]
+              def populate(): Unit =
+                patmat.javaClassesByUnit.get(sym.pos.source) match {
+                  case Some(classes) =>
+                    classes.find(!seen(_)) match {
+                      case Some(unseen) =>
+                        seen += unseen
+                        unseen.initialize.companionSymbol.moduleClass.initialize
+                        if (unseen.hasAttachment[PermittedSubclassSymbols]) initChildren(unseen)
+                        populate()
+                      case _ =>
+                    }
+                  case _ =>
+                }
+              populate()
           }
-        })
-      }
       initChildren(selectorTp.typeSymbol)
 
       def finish(cases: List[CaseDef], matchType: Type) =

test/files/neg/t12159g.check

@@ -0,0 +1,7 @@
+t.scala:4: warning: match may not be exhaustive.
+It would fail on the following inputs: Oz(), Z()
+  def n(a: X) = a match { case _: Y => 42 }
+                ^
+error: No warnings can be incurred under -Werror.
+1 warning
+1 error

test/files/neg/t12159g/X.java

@@ -1,9 +1,12 @@
 
 package p;
 public sealed interface X {
-  public default int x() { return 1; }
+  public default int x() { return 27; }
 }
 final class Y implements X { }
 final class O {
   final static class Z implements X { }
+  final static class Inner {
+    final static class Oz implements X { }
+  }
 }

test/files/neg/t12159g/t.scala

@@ -1,5 +1,5 @@
-
+// scalac: -Werror -Xlint
 package p
 class T {
-  def n(a: X) = a match { case _: Y => 0 }
+  def n(a: X) = a match { case _: Y => 42 }
 }