Merge pull request scala#7383 from lrytz/b11207

No static forwarders for bridges implementing abstract methods

Author: adriaanm

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

@@ -896,7 +896,10 @@ abstract class BCodeHelpers extends BCodeIdiomatic {
       debuglog(s"Potentially conflicting names for forwarders: $conflictingNames")
 
       for (m <- moduleClass.info.membersBasedOnFlags(BCodeHelpers.ExcludedForwarderFlags, symtab.Flags.METHOD)) {
-        if (m.isType || m.isDeferred || (m.owner eq definitions.ObjectClass) || m.isConstructor)
+        // Fix for scala/bug#11207, see https://github.com/scala/scala/pull/7035/files#r226274350. This makes sure that 2.12.8 generates
+        // the same forwarder methods as in 2.12.6 (but includes bridge flags). In 2.13 we don't generate any forwarders for bridges.
+        val bridgeImplementingAbstract = m.isBridge && m.nextOverriddenSymbol.isDeferred
+        if (m.isType || m.isDeferred || bridgeImplementingAbstract || (m.owner eq definitions.ObjectClass) || m.isConstructor)
           debuglog(s"No forwarder for '$m' from $jclassName to '$moduleClass': ${m.isType} || ${m.isDeferred} || ${m.owner eq definitions.ObjectClass} || ${m.isConstructor}")
         else if (conflictingNames(m.name))
           log(s"No forwarder for $m due to conflict with ${linkedClass.info.member(m.name)}")

test/junit/scala/tools/nsc/backend/jvm/BytecodeTest.scala

@@ -16,18 +16,28 @@ class BytecodeTest extends BytecodeTesting {
   import compiler._
 
   @Test
-  def bridgeFlag(): Unit = {
+  def staticForwardersBridgeFlag(): Unit = {
     val code =
-      """ A { def f: Object = null }
-        |object B extends A { override def f: String = "b" }
+      """ A {
+        |  def f: Object = null
+        |  def g: Object
+        |}
+        |object B extends A {
+        |  override def f: String = "b" // "bridge" forwarder
+        |  def g: String = "b"          // no "bridge" forwarder, as the overridden method is abstract, scala/bug#11207
+        |}
+        |case class K(x: Int, s: String)
       """.stripMargin
-    for (base <- List("trait", "class")) {
-      val List(a, bMirror, bModule) = compileClasses(base + code)
+    for (base <- List("trait", "abstract class")) {
+      val List(a, bMirror, bModule, kClass, kModule) = compileClasses(base + code)
       assertEquals("B", bMirror.name)
-      assertEquals(List("f()Ljava/lang/Object;0x49", "f()Ljava/lang/String;0x9"),
+      assertEquals(List("f()Ljava/lang/Object;0x49", "f()Ljava/lang/String;0x9", "g()Ljava/lang/String;0x9"),
         bMirror.methods.asScala
-          .filter(_.name == "f")
+          .filter(m => m.name == "f" || m.name == "g")
           .map(m => m.name + m.desc + "0x" + Integer.toHexString(m.access)).toList.sorted)
+      assertEquals("K", kClass.name)
+      val List(app) = kClass.methods.asScala.filter(_.name == "apply").toList
+      assertEquals("apply(ILjava/lang/String;)LK;0x9", app.name + app.desc + "0x" + Integer.toHexString(app.access))
     }
   }