Fix #3476: Add Artifact flag to closures

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -805,7 +805,7 @@ object desugar {
    *  If `inlineable` is true, tag $anonfun with an @inline annotation.
    */
   def makeClosure(params: List[ValDef], body: Tree, tpt: Tree = TypeTree(), inlineable: Boolean)(implicit ctx: Context) = {
-    var mods = synthetic
+    var mods = synthetic | Artifact
     if (inlineable) mods |= Inline
     Block(
       DefDef(nme.ANON_FUN, Nil, params :: Nil, tpt, body).withMods(mods),

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

@@ -12,6 +12,7 @@ import core.TypeErasure.erasure
 import core.Types._
 import core.classfile.ClassfileConstants
 import ast.Trees._
+import SymUtils._
 import TypeUtils._
 import java.lang.StringBuilder
 
@@ -27,8 +28,11 @@ object GenericSignatures {
    *  @param info The type of the symbol
    *  @return The signature if it could be generated, `None` otherwise.
    */
-  def javaSig(sym0: Symbol, info: Type)(implicit ctx: Context): Option[String] =
-    javaSig0(sym0, info)(ctx.withPhase(ctx.erasurePhase))
+  def javaSig(sym0: Symbol, info: Type)(implicit ctx: Context): Option[String] = {
+    // Avoid generating a signature for local symbols.
+    if (sym0.isLocal) None
+    else javaSig0(sym0, info)(ctx.withPhase(ctx.erasurePhase))
+  }
 
   @noinline
   private final def javaSig0(sym0: Symbol, info: Type)(implicit ctx: Context): Option[String] = {

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

@@ -341,7 +341,7 @@ object LambdaLift {
         local.copySymDenotation(
           owner = newOwner,
           name = newName(local),
-          initFlags = local.flags &~ Module &~ Final | Private | maybeStatic,
+          initFlags = local.flags &~ Module &~ Final | Private | Lifted | maybeStatic,
             // drop Module because class is no longer a singleton in the lifted context.
           info = liftedInfo(local)).installAfter(thisPhase)
       }

tests/generic-java-signatures/i3476.check

@@ -0,0 +1 @@
+OK

tests/generic-java-signatures/i3476.scala

@@ -0,0 +1,98 @@
+object Test {
+
+  def hasGenericSignature(cls: Class[_], methName: String): Boolean = {
+    cls.getDeclaredMethods().find(_.getName.contains(methName)) match {
+      case None => throw new NoSuchMethodError(s"No $methName in ${cls.getName}")
+      case Some(meth) => meth.getTypeParameters.nonEmpty
+    }
+  }
+
+  def checkHasGenericSignature(cls: Class[_], methName: String): Unit =
+    assert(hasGenericSignature(cls, methName))
+
+  def checkDoesntHaveGenericSignature(cls: Class[_], methName: String): Unit =
+    assert(!hasGenericSignature(cls, methName))
+
+  def main(args: Array[String]): Unit = {
+
+    checkHasGenericSignature(classOf[TopLevelClass], "meth")
+    checkHasGenericSignature(classOf[AbstractTopLevelClass], "meth")
+    checkHasGenericSignature(classOf[TopLevelClass#InsideClass], "meth")
+    checkHasGenericSignature(classOf[TopLevelClass#AbstractInsideClass], "meth")
+    checkDoesntHaveGenericSignature(new TopLevelClass().localClass, "meth")
+    checkDoesntHaveGenericSignature(new TopLevelClass().otherLocalClass, "meth")
+
+    checkHasGenericSignature(TopLevelObject.getClass, "meth")
+    checkHasGenericSignature(classOf[TopLevelObject.InsideObject], "meth")
+    checkHasGenericSignature(classOf[TopLevelObject.AbstractInsideObject], "meth")
+    checkDoesntHaveGenericSignature(TopLevelObject.localClass, "meth")
+    checkDoesntHaveGenericSignature(TopLevelObject.otherLocalClass, "meth")
+
+    println("OK")
+  }
+}
+
+object TopLevelObject {
+  def meth[T](x: T): T = x
+
+  def localObject: Class[_] = {
+    object LocalObject {
+      def meth[T](x: T): T = x
+    }
+    LocalObject.getClass
+  }
+
+  def localClass: Class[_] = {
+    class LocalClass {
+      def meth[T](x: T): T = x
+    }
+    classOf[LocalClass]
+  }
+
+  val otherLocalClass: Class[_] = {
+    class LocalClass {
+      def meth[T](x: T): T = x
+    }
+    classOf[LocalClass]
+  }
+
+  class InsideObject {
+    def meth[T](x: T): T = x
+  }
+
+  abstract class AbstractInsideObject {
+    def meth[T](x: T): T = x
+  }
+}
+
+class TopLevelClass {
+
+  def meth[T](x: T): T = x
+
+  def localClass: Class[_] = {
+    class LocalClass {
+      def meth[T](x: T): T = x
+    }
+    classOf[LocalClass]
+  }
+
+  val otherLocalClass: Class[_] = {
+    class LocalClass {
+      def meth[T](x: T): T = x
+    }
+    classOf[LocalClass]
+  }
+
+  class InsideClass {
+    def meth[T](x: T): T = x
+  }
+
+  abstract class AbstractInsideClass {
+    def meth[T](x: T): T = x
+  }
+}
+
+abstract class AbstractTopLevelClass {
+  def meth[T](x: T): T = x
+}
+