Generate static forwarders for object members in companion interface

Same change implemented five years ago in Scala 2:
scala/scala#5131

Fixes #13572.

This PR was backported to 3.1.0-RC3 in #13616, this lets us bump the
previousDottyVersion to make the mima checks pass even though this PR
introduces new public member (and while we're at it, we can reset the
mima filter list).

Author: smarter

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

@@ -292,7 +292,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
       emitAnnotations(cnode, claszSymbol.annotations ++ ssa)
 
       if (!isCZStaticModule && !isCZParcelable) {
-        val skipStaticForwarders = (claszSymbol.isInterface || claszSymbol.is(Module) || ctx.settings.XnoForwarders.value)
+        val skipStaticForwarders = (claszSymbol.is(Module) || ctx.settings.XnoForwarders.value)
         if (!skipStaticForwarders) {
           val lmoc = claszSymbol.companionModule
           // add static forwarders if there are no name conflicts; see bugs #363 and #1735

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

@@ -1,3 +1,6 @@
+## Many of these tests fail because CompilationTests.pickling does not handle
+## tests containing java files correctly
+
 derive-generic.scala
 eff-dependent.scala
 enum-java
@@ -38,3 +41,4 @@ i12753
 t6138
 t6138-2
 i12656.scala
+trait-static-forwarder

project/Build.scala

@@ -81,7 +81,7 @@ object Build {
    *  set to 3.1.3. If it is going to be 3.1.0, it must be set to the latest
    *  3.0.x release.
    */
-  val previousDottyVersion = "3.0.2"
+  val previousDottyVersion = "3.1.0-RC3"
 
   object CompatMode {
     final val BinaryCompatible = 0

project/MiMaFilters.scala

@@ -4,48 +4,5 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object MiMaFilters {
   val Library: Seq[ProblemFilter] = Seq(
-    // Experimental API for saferExceptions
-    exclude[MissingClassProblem]("scala.CanThrow"),
-    exclude[MissingClassProblem]("scala.CanThrow$package"),
-    exclude[MissingClassProblem]("scala.CanThrow$package$"),
-    exclude[MissingClassProblem]("scala.unsafeExceptions"),
-    exclude[MissingClassProblem]("scala.unsafeExceptions$"),
-    exclude[MissingFieldProblem]("scala.runtime.stdLibPatches.language#experimental.saferExceptions"),
-    exclude[MissingClassProblem]("scala.runtime.stdLibPatches.language$experimental$saferExceptions$"),
-
-    // New APIs that will be introduced in 3.1.0
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule.Wildcard"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule.WildcardTypeTest"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SourceFileMethods.getJPath"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SourceFileMethods.name"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SourceFileMethods.path"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SourceFileMethods.getJPath"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SourceFileMethods.name"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SourceFileMethods.path"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#UnapplyModule.apply"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#UnapplyModule.apply"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule.TypedOrTestTypeTest"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule.TypedOrTest"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule.TypedOrTestMethods"),
-    exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TypeReprMethods.isTupleN"),
-
-    // TODO: Remove those filters after releasing 3.1.0:
-    exclude[DirectMissingMethodProblem]("scala.CanEqual.canEqualSeqs"),
-    exclude[DirectMissingMethodProblem]("scala.CanEqual.canEqualOptions"),
-    exclude[DirectMissingMethodProblem]("scala.CanEqual.canEqualOption"),
-    exclude[DirectMissingMethodProblem]("scala.CanEqual.canEqualEither"),
-    exclude[DirectMissingMethodProblem]("scala.Tuple.canEqualEmptyTuple"),
-    exclude[DirectMissingMethodProblem]("scala.Tuple.canEqualTuple"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule.WildcardTypeTest"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule.Wildcard"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule.TypedOrTestTypeTest"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule.TypedOrTest"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule.TypedOrTestMethods"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TypeReprMethods.isTupleN"),
-    exclude[MissingClassProblem]("scala.quoted.Quotes$reflectModule$TypedOrTestMethods"),
-    exclude[MissingClassProblem]("scala.quoted.Quotes$reflectModule$TypedOrTestModule"),
-    exclude[MissingClassProblem]("scala.quoted.Quotes$reflectModule$WildcardModule"),
-    exclude[MissingClassProblem]("scala.runtime.$throws$package"),
-    exclude[MissingClassProblem]("scala.runtime.$throws$package$"),
   )
 }

tests/run/trait-static-forwarder.check

@@ -0,0 +1 @@
+42

tests/run/trait-static-forwarder/Test.java

@@ -0,0 +1,5 @@
+public final class Test {
+    public static void main(String... args) {
+        System.out.println(T.foo());
+    }
+}

tests/run/trait-static-forwarder/forwarders.scala

@@ -0,0 +1,5 @@
+trait T
+
+object T {
+  def foo = 42
+}