SI-9390 Emit local defs that don't capture this as static

This avoids unnecessary memory retention, and allows lambdas
that call the local methods to be serializable, regardless of
whether or not the enclosing class is serializable.

The second point is especially pressing, given that the enclosing
class for local methods defined in a used to be the (serializable)
anonymous function class, but as of Scala 2.12 will be the enclosing
class of the lambda.

This change is similar in spirit to SI-9408 / 93bee55e.

1 files changed, 31 insertions, 0 deletions

diff --git a/test/files/run/t9390b.scala b/test/files/run/t9390b.scala
new file mode 100644
index 0000000000..439e21e0a0
--- /dev/null
+++ b/test/files/run/t9390b.scala
@@ -0,0 +1,31 @@
+class C { // C is not serializable
+  def foo = (x: Int) => (y: Int) => x + y
+  def bar = (x: Int) => (y: Int) => {toString; x + y}
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val c = new C
+    val f = c.foo
+    assert(f(1)(2) == 3)
+    val f1 = serializeDeserialize(f)
+    assert(f1(1)(2) == 3)
+
+    try {
+      serializeDeserialize(c.bar)
+      assert(false)
+    } catch {
+      case _: java.io.NotSerializableException =>
+        // expected, lambda transitively refers to this
+    }
+  }
+
+  def serializeDeserialize[T <: AnyRef](obj: T): T = {
+    import java.io._
+    val buffer = new ByteArrayOutputStream
+    val out = new ObjectOutputStream(buffer)
+    out.writeObject(obj)
+    val in = new ObjectInputStream(new ByteArrayInputStream(buffer.toByteArray))
+    in.readObject.asInstanceOf[T]
+  }
+}