Hide problematic static forwarders

compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala

@@ -21,6 +21,7 @@ import dotty.tools.dotc.core.Names.Name
 import dotty.tools.dotc.core.NameKinds.ExpandedName
 import dotty.tools.dotc.core.Signature
 import dotty.tools.dotc.core.StdNames._
+import dotty.tools.dotc.core.NameKinds
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.Types
 import dotty.tools.dotc.core.Types._
@@ -507,7 +508,7 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
      *
      * must-single-thread
      */
-    private def addForwarder(jclass: asm.ClassVisitor, module: Symbol, m: Symbol): Unit = {
+    private def addForwarder(jclass: asm.ClassVisitor, module: Symbol, m: Symbol, isSynthetic: Boolean): Unit = {
       val moduleName     = internalName(module)
       val methodInfo     = module.thisType.memberInfo(m)
       val paramJavaTypes: List[BType] = methodInfo.firstParamTypes map toTypeKind
@@ -518,9 +519,10 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
        *  and we don't know what classes might be subclassing the companion class.  See SI-4827.
        */
       // TODO: evaluate the other flags we might be dropping on the floor here.
-      // TODO: ACC_SYNTHETIC ?
       val flags = GenBCodeOps.PublicStatic | (
         if (m.is(JavaVarargs)) asm.Opcodes.ACC_VARARGS else 0
+      ) | (
+        if (isSynthetic) asm.Opcodes.ACC_SYNTHETIC else 0
       )
 
       // TODO needed? for(ann <- m.annotations) { ann.symbol.initialize }
@@ -595,7 +597,16 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
           report.log(s"No forwarder for non-public member $m")
         else {
           report.log(s"Adding static forwarder for '$m' from $jclassName to '$moduleClass'")
-          addForwarder(jclass, moduleClass, m)
+          // It would be simpler to not generate forwarders for these methods,
+          // but that wouldn't be binary-compatible with Scala 3.0.0, so instead
+          // we generate ACC_SYNTHETIC forwarders so Java compilers ignore them.
+          val isSynthetic =
+            m0.name.is(NameKinds.SyntheticSetterName) ||
+            // Only hide bridges generated at Erasure, mixin forwarders are also
+            // marked as bridge but shouldn't be hidden since they don't have a
+            // non-bridge overload.
+            m0.is(Bridge) && m0.initial.validFor.firstPhaseId == erasurePhase.next.id
+          addForwarder(jclass, moduleClass, m, isSynthetic)
         }
       }
     }

compiler/test/dotc/run-test-pickling.blacklist

@@ -34,3 +34,4 @@ typeclass-derivation3.scala
 varargs-abstract
 zero-arity-case-class.scala
 i12194.scala
+i12753

tests/run/i12753.check

@@ -0,0 +1,28 @@
+1
+Dbr
+1
+1
+2
+1
+1
+1
+1
+2
+1
+1
+synthetic public static C D.foo(int)
+public static D D.foo(int)
+public static D D.t()
+synthetic public static java.lang.Object D.bar()
+public static java.lang.String D.bar()
+public static int O.a()
+public static int O.b()
+public static int O.c()
+public static int O.d()
+public static int O.i()
+public static int O.j()
+public static int O.k()
+public static int O.l()
+synthetic public static void O.T$_setter_$a_$eq(int)
+public static void O.b_$eq(int)
+public static void O.j_$eq(int)

tests/run/i12753/C.scala

@@ -0,0 +1,34 @@
+trait C[This <: C[This]]
+
+trait COps[This <: C[This]] {
+  def t: This
+  def foo(x: Int): This = t
+  def bar: Object = "Cbr"
+}
+
+class D extends C[D] {
+  def x = 1
+}
+object D extends COps[D] {
+  def t = new D
+  override def foo(x: Int): D = super.foo(x)
+  override def bar: String = "Dbr"
+}
+
+trait T {
+  val a = 1
+  var b = 1
+  lazy val c = 1
+  def d = 1
+
+  val i: Int
+  var j: Int
+  lazy val k: Int = 1
+  def l: Int
+}
+object O extends T {
+  val i: Int = 1
+  var j: Int = 1
+  override lazy val k: Int = 1
+  def l: Int = 1
+}

tests/run/i12753/Test.java

@@ -0,0 +1,36 @@
+public class Test {
+  public static void s(Object s) {
+    System.out.println(s);
+  }
+
+  public static void statics(Class<?> c) {
+    java.lang.reflect.Method[] ms = c.getDeclaredMethods();
+    java.util.Arrays.sort(ms, (a, b) -> a.toString().compareTo(b.toString()));
+    for (java.lang.reflect.Method a : ms) {
+      if (java.lang.reflect.Modifier.isStatic(a.getModifiers()))
+        s((a.isSynthetic() ? "synthetic " : "") + a);
+    }
+  }
+
+  public static void main(String[] args) {
+    s(D.foo(1).x());
+    s(D.bar().trim());
+
+    s(O.a());
+    s(O.b());
+    O.b_$eq(2);
+    s(O.b());
+    s(O.c());
+    s(O.d());
+
+    s(O.i());
+    s(O.j());
+    O.j_$eq(2);
+    s(O.j());
+    s(O.k());
+    s(O.l());
+
+    statics(D.class);
+    statics(O.class);
+  }
+}