SI-8134 SI-5954 Fix companions in package object under separate comp.

The tests cases enclosed exhibited two failures modes under
separate compilation.

  1. When a synthetic companion object for a case- or implicit-class
     defined in a package object is called for,
     `Namer#ensureCompanionObject` is used to check for an explicitly
     defined companion before decided to create a synthetic one.
     This lookup of an existing companion symbol by `companionObjectOf`
     would locate a symbol backed by a class file which was in the
     scope of the enclosing package class. Furthermore, because the
     owner of that symbol is the package object class that has now
     been noted as corresponding to a source file in the current
     run, the class-file backed module symbol is *also* deemed to
     be from the current run. (This logic is in `Run#compiles`.)

     Thinking the companion module already existed, no synthetic
     module was created, which would lead to a crash in extension
     methods, which needs to add methods to it.

  2. In cases when the code explicitly contains the companion pair,
     we still ran into problems in the backend whereby the class-file
     based and source-file based symbols for the module ended up in
     the same scope (of the package class). This tripped an assertion
     in `Symbol#companionModule`.

We get into these problems because of the eager manner in which
class-file based package object are opened in `openPackageModule`.
The members of the module are copied into the scope of the enclosing
package:

    scala> ScalaPackage.info.member(nme.List)
    res0: $r#59116.intp#45094.global#28436.Symbol#29451 = value List#2462

    scala> ScalaPackage.info.member(nme.PACKAGE).info.member(nme.List)
    res1: $r#59116.intp#45094.global#28436.Symbol#29451 = value List#2462

This seems to require a two-pronged defense:

  1. When we attach a pre-existing symbol for a package object symbol
     to the tree of its new source, unlink the "forwarder" symbols
     (its decls from the enclosing
     package class.

  2. In `Flatten`, in the spirit of `replaceSymbolInCurrentScope`,
     remove static member modules from the scope of the enclosing
     package object (aka `exitingFlatten(nestedModule.owner)`).

This commit also removes the warnings about defining companions
in package objects and converts those neg tests to pos (with
-Xfatal-warnings to prove they are warning free.)

Defining nested classes/objects in package objects still has
a drawback: you can't shift a class from the package to the
package object, or vice versa, in a binary compatible manner,
because of the `package$` prefix on the flattened name of
nested classes. For this reason, the `-Xlint` warning about
this remains. This issue is tracked as SI-4344.

However, if one heeds this warning and incrementatlly recompiles,
we no longer need to run into a DoubleDefinition error (which
was dressed up with a more specific diagnostic in SI-5760.)
The neg test case for that bug has been converted to a pos.

9 files changed, 0 insertions, 107 deletions

diff --git a/test/files/neg/package-ob-case.check b/test/files/neg/package-ob-case.check
deleted file mode 100644
index 9b0ede1c6d..0000000000
--- a/test/files/neg/package-ob-case.check
+++ /dev/null
@@ -1,10 +0,0 @@
-package-ob-case.scala:3: warning: it is not recommended to define classes/objects inside of package objects.
-If possible, define class X in package foo instead.
-    case class X(z: Int) { }
-               ^
-package-ob-case.scala:3: warning: class X should be placed directly in package foo instead of package object foo. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.
-    case class X(z: Int) { }
-               ^
-error: No warnings can be incurred under -Xfatal-warnings.
-two warnings found
-one error found
diff --git a/test/files/neg/package-ob-case.flags b/test/files/neg/package-ob-case.flags
deleted file mode 100644
index 6c1dd108ae..0000000000
--- a/test/files/neg/package-ob-case.flags
+++ /dev/null
@@ -1 +0,0 @@
--Xfatal-warnings -Xlint
\ No newline at end of file
diff --git a/test/files/neg/package-ob-case.scala b/test/files/neg/package-ob-case.scala
deleted file mode 100644
index 91a1fb7e48..0000000000
--- a/test/files/neg/package-ob-case.scala
+++ /dev/null
@@ -1,5 +0,0 @@
-package foo {
-  package object foo {
-    case class X(z: Int) { }
-  }
-}
diff --git a/test/files/neg/t5760-pkgobj-warn.check b/test/files/neg/t5760-pkgobj-warn.check
deleted file mode 100644
index a89398c3f7..0000000000
--- a/test/files/neg/t5760-pkgobj-warn.check
+++ /dev/null
@@ -1,4 +0,0 @@
-stalepkg_2.scala:6: error: Foo is already defined as class Foo in package object stalepkg
-  class Foo
-        ^
-one error found
diff --git a/test/files/neg/t5760-pkgobj-warn/stalepkg_1.scala b/test/files/neg/t5760-pkgobj-warn/stalepkg_1.scala
deleted file mode 100644
index ed4b731bb0..0000000000
--- a/test/files/neg/t5760-pkgobj-warn/stalepkg_1.scala
+++ /dev/null
@@ -1,11 +0,0 @@
-
-package object stalepkg {
-  class Foo
-}
-
-package stalepkg {
-  object Test {
-    def main(args: Array[String]) {
-    }
-  }
-}
diff --git a/test/files/neg/t5760-pkgobj-warn/stalepkg_2.scala b/test/files/neg/t5760-pkgobj-warn/stalepkg_2.scala
deleted file mode 100644
index 9abcdbab17..0000000000
--- a/test/files/neg/t5760-pkgobj-warn/stalepkg_2.scala
+++ /dev/null
@@ -1,11 +0,0 @@
-
-package object stalepkg {
-}
-
-package stalepkg {
-  class Foo
-  object Test {
-    def main(args: Array[String]) {
-    }
-  }
-}
diff --git a/test/files/neg/t5954.check b/test/files/neg/t5954.check
deleted file mode 100644
index 3950d14e4e..0000000000
--- a/test/files/neg/t5954.check
+++ /dev/null
@@ -1,18 +0,0 @@
-t5954.scala:36: warning: class D should be placed directly in package A instead of package object A. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.
-  case class D()
-             ^
-t5954.scala:35: warning: object C should be placed directly in package A instead of package object A. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.
-  object C
-         ^
-t5954.scala:34: warning: trait C should be placed directly in package A instead of package object A. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.
-  trait C
-        ^
-t5954.scala:33: warning: object B should be placed directly in package A instead of package object A. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.
-  object B
-         ^
-t5954.scala:32: warning: class B should be placed directly in package A instead of package object A. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.
-  class B
-        ^
-error: No warnings can be incurred under -Xfatal-warnings.
-5 warnings found
-one error found
diff --git a/test/files/neg/t5954.flags b/test/files/neg/t5954.flags
deleted file mode 100644
index 85d8eb2ba2..0000000000
--- a/test/files/neg/t5954.flags
+++ /dev/null
@@ -1 +0,0 @@
--Xfatal-warnings
diff --git a/test/files/neg/t5954.scala b/test/files/neg/t5954.scala
deleted file mode 100644
index 3ccb5ed3ff..0000000000
--- a/test/files/neg/t5954.scala
+++ /dev/null
@@ -1,46 +0,0 @@
-// if you ever think you've fixed the underlying reason for the warning
-// imposed by SI-5954, then here's a test that should pass with two "succes"es
-//
-//import scala.tools.partest._
-//
-//object Test extends DirectTest {
-//  def code = ???
-//
-//  def problemCode = """
-//    package object A {
-//      class B
-//      object B
-//      case class C()
-//    }
-//  """
-//
-//  def compileProblemCode() = {
-//    val classpath = List(sys.props("partest.lib"), testOutput.path) mkString sys.props("path.separator")
-//    compileString(newCompiler("-cp", classpath, "-d", testOutput.path))(problemCode)
-//  }
-//
-//  def show() : Unit = {
-//    for (i <- 0 until 2) {
-//      compileProblemCode()
-//      println(s"success ${i + 1}")
-//    }
-//  }
-//}
-
-package object A {
-  // these should be prevented by the implementation restriction
-  class B
-  object B
-  trait C
-  object C
-  case class D()
-  // all the rest of these should be ok
-  class E
-  object F
-  val g = "omg"
-  var h = "wtf"
-  def i = "lol"
-  type j = String
-  class K(val k : Int) extends AnyVal
-  implicit class L(val l : Int)
-}