Populate children of Java sealed hierarchy

Required for checking permitted subclasses
and for exhaustiveness of patterns.

Co-authored-by: Lukas Rytz <lukas.rytz@gmail.com>

src/compiler/scala/tools/nsc/javac/JavaParsers.scala

@@ -19,6 +19,7 @@ package javac
 import symtab.Flags
 import JavaTokens._
 import scala.annotation._
+import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
 import scala.language.implicitConversions
 import scala.reflect.internal.util.{ListOfNil, Position}
@@ -45,6 +46,7 @@ trait JavaParsers extends ast.parser.ParsersCommon with JavaScanners {
 
   abstract class JavaParser extends ParserCommon {
     val in: JavaScanner
+    def unit: CompilationUnit
 
     def freshName(prefix : String): Name
     protected implicit def i2p(offset : Int) : Position
@@ -838,6 +840,7 @@ trait JavaParsers extends ast.parser.ParsersCommon with JavaScanners {
       else Nil
 
     def classDecl(mods: Modifiers): List[Tree] = {
+      if (mods.hasFlag(SEALED)) patmat.javaClassesByUnit(unit.source) = mutable.Set.empty
       accept(CLASS)
       val pos = in.currentPos
       val name = identForType()
@@ -904,6 +907,7 @@ trait JavaParsers extends ast.parser.ParsersCommon with JavaScanners {
     }
 
     def interfaceDecl(mods: Modifiers): List[Tree] = {
+      if (mods.hasFlag(SEALED)) patmat.javaClassesByUnit(unit.source) = mutable.Set.empty
       accept(INTERFACE)
       val pos = in.currentPos
       val name = identForType()

src/compiler/scala/tools/nsc/transform/patmat/PatternMatching.scala

@@ -13,9 +13,10 @@
 package scala.tools.nsc.transform.patmat
 
 import scala.annotation.tailrec
+import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
 import scala.reflect.internal.{Mode, Types}
-import scala.reflect.internal.util.Statistics
+import scala.reflect.internal.util.{SourceFile, Statistics}
 import scala.tools.nsc.Global
 import scala.tools.nsc.ast
 import scala.tools.nsc.transform.{Transform, TypingTransformers}
@@ -58,6 +59,9 @@ trait PatternMatching extends Transform
 
   val phaseName: String = "patmat"
 
+  /** Symbols to force for determining children of sealed Java classes. */
+  val javaClassesByUnit = perRunCaches.newMap[SourceFile, mutable.Set[Symbol]]()
+
   def newTransformer(unit: CompilationUnit): AstTransformer = new MatchTransformer(unit)
 
   class MatchTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {

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

@@ -795,6 +795,8 @@ trait Namers extends MethodSynthesis {
       tree.symbol = enterClassSymbol(tree)
       tree.symbol setInfo completerOf(tree)
 
+      if (tree.symbol.isJava) patmat.javaClassesByUnit.get(tree.symbol.pos.source).foreach(_.addOne(tree.symbol))
+
       if (mods.isCase) {
         val m = ensureCompanionObject(tree, caseModuleDef)
         m.moduleClass.updateAttachment(new ClassForCaseCompanionAttachment(tree))

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

@@ -2653,6 +2653,20 @@ 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)
+          }
+        })
+      }
+      initChildren(selectorTp.typeSymbol)
+
       def finish(cases: List[CaseDef], matchType: Type) =
         treeCopy.Match(tree, selector1, cases) setType matchType
 

test/files/neg/t12159d.check

@@ -1,7 +1,7 @@
-s.scala:5: error: illegal inheritance from sealed class H
-class S extends H {
-                ^
-s.scala:8: error: illegal inheritance from sealed trait I
-trait T extends I {
-                ^
-2 errors
+t_3.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: W()
+    x match {
+    ^
+error: No warnings can be incurred under -Werror.
+1 warning
+1 error

test/files/neg/t12159d/X_3.java

@@ -0,0 +1,14 @@
+// javaVersion: 17+
+package p;
+
+sealed abstract public class X_3 {
+}
+
+final class W extends X_3 {
+}
+
+final class Y extends X_3 {
+}
+
+final class Z extends X_3 {
+}

test/files/neg/t12159d/t_3.scala

@@ -0,0 +1,12 @@
+// javaVersion: 17+
+// scalac: -Werror
+package p
+
+class C {
+  def f(x: X_3) =
+    x match {
+      case y: Y => y.toString
+      case z: Z => z.toString
+    }
+}
+

test/files/neg/t12159e.check

@@ -0,0 +1,11 @@
+t.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: W()
+    x match {
+    ^
+t.scala:12: warning: match may not be exhaustive.
+It would fail on the following inputs: Z(), Z2()
+    x match {
+    ^
+error: No warnings can be incurred under -Werror.
+2 warnings
+1 error

test/files/neg/t12159e/X.java

@@ -0,0 +1,20 @@
+// javaVersion: 17+
+package p;
+
+sealed abstract public class X {
+}
+
+final class W extends X {
+}
+
+final class Y extends X {
+}
+
+sealed class Z extends X permits Z1, Z2 {
+}
+
+final class Z1 extends Z {
+}
+
+final class Z2 extends Z {
+}

test/files/neg/t12159e/t.scala

@@ -0,0 +1,18 @@
+// javaVersion: 17+
+// scalac: -Werror
+package p
+
+class C {
+  def f(x: X) =
+    x match {
+      case y: Y => y.toString
+      case z: Z => z.toString
+    }
+  def g(x: X) =
+    x match {
+      case w: W => w.toString
+      case y: Y => y.toString
+      case z: Z1 => z.toString
+    }
+}
+

test/files/neg/t12159f.check

@@ -0,0 +1,11 @@
+t.scala:7: warning: match may not be exhaustive.
+It would fail on the following input: W()
+    x match {
+    ^
+t.scala:12: warning: match may not be exhaustive.
+It would fail on the following inputs: Z(), Z2()
+    x match {
+    ^
+error: No warnings can be incurred under -Werror.
+2 warnings
+1 error

test/files/neg/t12159f/X.java

@@ -0,0 +1,14 @@
+// javaVersion: 17+
+package p;
+
+sealed abstract public class X {
+}
+
+final class W extends X {
+}
+
+final class Y extends X {
+}
+
+sealed class Z extends X permits Z1, Z2 {
+}

test/files/neg/t12159f/Z.java

@@ -0,0 +1,8 @@
+// javaVersion: 17+
+package p;
+
+final class Z1 extends Z {
+}
+
+final class Z2 extends Z {
+}

test/files/neg/t12159f/t.scala

@@ -0,0 +1,18 @@
+// javaVersion: 17+
+// scalac: -Werror
+package p
+
+class C {
+  def f(x: X) =
+    x match {
+      case y: Y => y.toString
+      case z: Z => z.toString
+    }
+  def g(x: X) =
+    x match {
+      case w: W => w.toString
+      case y: Y => y.toString
+      case z: Z1 => z.toString
+    }
+}
+