SI-3832 Don't lift methods in aux constructor trailing stats as STATIC

SI-1909 modified LambdaLift to lift in auxiliary constructors methods as STATIC
so they could be called before the self-constructor was called.

That allowed for:

     class Foo (x: Int) {
       def this() = this( {
         def bar() = 5
         bar
       })
    }

However, if the method is in a statement that trails the self constructor call,
this is unnecessary and in fact incorrect as it robs the lifted method of `this`.

This commit uses the machinery established in SI-6666 to limit the STATIC-ness
of lifted methods to those used in arguments for self-constructor calls.

This is used exclusively; the `isAuxillaryConstructor` check wasn't the right
way to solve this, as was seen by the regression it caused in SI-3832.
A new test case shows that we can statically lift methods in super-constructor
calls, rather than just self-constructor calls.

We also have to avoid statically lifting objects in these positions. For now,
I just emit a dev warning that a VerifyError is in your future. With some more
thought we could escalate that to a implementation restriction and emit an error.

1 files changed, 9 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
index 515fa66cfa..acef2a50d8 100644
--- a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
+++ b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
@@ -436,8 +436,15 @@ abstract class LambdaLift extends InfoTransform {
     private def liftDef(tree: Tree): Tree = {
       val sym = tree.symbol
       val oldOwner = sym.owner
-      if (sym.owner.isAuxiliaryConstructor && sym.isMethod)  // # bug 1909
-    	  sym setFlag STATIC
+      if (sym.isMethod && isUnderConstruction(sym.owner.owner)) { // # bug 1909
+         if (sym.isModule) { // Yes, it can be a module and a method, see comments on `isModuleNotMethod`!
+           // TODO promote to an implementation restriction if we can reason that this *always* leads to VerifyError.
+           // See neg/t1909-object.scala
+           def msg = s"SI-1909 Unable to STATICally lift $sym, which is defined in the self- or super-constructor call of ${sym.owner.owner}. A VerifyError is likely."
+           devWarning(tree.pos, msg)
+          } else sym setFlag STATIC
+      }
+
       sym.owner = sym.owner.enclClass
       if (sym.isClass) sym.owner = sym.owner.toInterface
       if (sym.isMethod) sym setFlag LIFTED