Merge pull request #4652 from retronym/ticket/9408

SI-9408 Avoid capturing outer class in local classes.

1 files changed, 61 insertions, 0 deletions

diff --git a/test/files/run/t9408.scala b/test/files/run/t9408.scala
new file mode 100644
index 0000000000..231dca4ce7
--- /dev/null
+++ b/test/files/run/t9408.scala
@@ -0,0 +1,61 @@
+class Outer {
+  def assertNoFields(c: Class[_]) {
+    assert(c.getDeclaredFields.isEmpty)
+  }
+  def assertHasOuter(c: Class[_]) {
+    assert(c.getDeclaredFields.exists(_.getName.contains("outer")))
+  }
+  class Member
+  final class FinalMember
+
+  def test {
+    assertHasOuter(classOf[Member])
+    assertNoFields(classOf[FinalMember])
+    final class C
+    assertNoFields(classOf[C])
+    class D
+    assertNoFields(classOf[D])
+    (() => {class E; assertNoFields(classOf[E])}).apply()
+
+    // The outer reference elision currently runs on a class-by-class basis. If it cannot rule out that a class has
+    // subclasses, it will not remove the outer reference. A smarter analysis here could detect if no members of
+    // a sealed (or effectively sealed) hierarchy use the outer reference, the optimization could be performed.
+    class Parent
+    class Child extends Parent
+    assertHasOuter(classOf[Parent])
+
+    // Note: outer references (if they haven't been elided) are used in pattern matching as follows.
+    // This isn't relevant to term-owned classes, as you can't refer to them with a prefix that includes
+    // the outer class.
+    val outer1 = new Outer
+    val outer2 = new Outer
+    (new outer1.Member: Any) match {
+      case _: outer2.Member => sys.error("wrong match!")
+      case _: outer1.Member => // okay
+    }
+
+    // ... continuing on that theme, note that `Member` isn't considered as a local class, it is owned by a the class
+    // `LocalOuter`, which itself happens to be term-owned. So we expect that it has an outer reference, and that this
+    // is respected in type tests.
+    class LocalOuter {
+      class Member
+      final class FinalMember
+    }
+    assertNoFields(classOf[LocalOuter])
+    assertHasOuter(classOf[LocalOuter#Member])
+    val localOuter1 = new LocalOuter
+    val localOuter2 = new LocalOuter
+    (new localOuter1.Member: Any) match {
+      case _: localOuter2.Member => sys.error("wrong match!")
+      case _: localOuter1.Member => // okay
+    }
+    // Final member classes still lose the outer reference.
+    assertNoFields(classOf[LocalOuter#FinalMember])
+  }
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    new Outer().test
+  }
+}