Fix #239 - handling of package objects

[odersky]

References to .package are now also inserted if the
accessed member comes from a class inherited by a package
object.

Closes #239

Review by @retronym

[odersky]

Note that -Ycheck caught the problem with the included test file before the fix was made.

[retronym]

Does this assign a position to Select(qual, TermName("package"))?

[odersky]

On Mon, Dec 15, 2014 at 12:43 AM, Jason Zaugg [email protected]
wrote:

In src/dotty/tools/dotc/transform/FirstTransform.scala
#282 (diff):

@@ -124,7 +124,7 @@ class FirstTransform extends MiniPhaseTransform with IdentityDenotTransformer wi
normalizeType {
val qual = tree.qualifier
qual.symbol.moduleClass.denot match {

•    case pkg: PackageClassDenotation if tree.symbol.maybeOwner.isPackageObject =>
  

•    case pkg: PackageClassDenotation if !tree.symbol.maybeOwner.is(Package) =>
     cpy.Select(tree)(qual select pkg.packageObj.symbol, tree.name)
  

Does this assign a position to Select(qual, TermName("package"))?

Yes, it's the position of qual.

• Martin

—
Reply to this email directly or view it on GitHub
https://github.com/lampepfl/dotty/pull/282/files#r21800912.

Martin Odersky
EPFL

[retronym]

There are some gaps with inherited implicit members:

package p {
  class C[A] { implicit def foo: M[A] = ??? }

  object `package` extends C[String]

  object test0 {
    def compute[A](implicit m: M[A]): A = ???
    val v = compute
    val v1: String = v
  }
}

trait M[A]

object test1 {

  def compute[A](implicit m: M[A]): A = ???

  import p._
  val v = compute
  val v1: String = v
}

I tested this with dotty (as at this PR) and scalac.

Dotty fails with:

./bin/dotc sandbox/test.scala
sandbox/test.scala:8: error: type mismatch:
 found   : => M[String](p.foo)
 required: M[(A? = p$C$$A)]
    val v = compute
                   ^
sandbox/test.scala:9: error: type mismatch:
 found   : p$C$$A(p.test0.v)
 required: String
    val v1: String = v
                     ^
sandbox/test.scala:20: error: type mismatch:
 found   : => M[String](p.foo)
 required: M[(A? = p$C$$A)]
  val v = compute
                 ^
sandbox/test.scala:21: error: type mismatch:
 found   : p$C$$A(test1.v)
 required: String
  val v1: String = v
                   ^
four errors found

Scalac compiles successfully.

[odersky]

Good catch. I added a patch that fixes this.

[retronym]

LGTM. Patching ASF seems to address the problem in a more centralized way than we managed in scalac.

You might like to try a few more test cases from scala/scala#4001. Sorry that I forgot to point out this one yesterday.

Perhaps the most esoteric one was related to insertion of an apply call for pack.O(), where O is defined in the package object.