Separate compilation violates package-protected accessibility

[eed3si9n]

This is a retroactive bug report on Scala 2.12.x and 2.13.0 ~ 1 since it seems to be fixed in Scala 2.13.2.

reproduction steps

using Scala 2.13.1

bar/B.scala

package bar

protected[bar] class B(x: Int)

foo/Test.scala

package example

import bar.B

object Test {
  def b = new B(1)
}

bash

mkdir -p bar/classes/
mkdir -p foo/classes/
$HOME/Applications/scala-2.13.1/bin/scalac bar/B.scala -d bar/classes
ls bar/classes/bar
# outputs B.class

$HOME/Applications/scala-2.13.1/bin/scalac -cp bar/classes/ foo/Test.scala -d foo/classes
ls foo/classes/example
# outputs Test$.class  Test.class

problem

The separate compilation violates protected[bar].

expectation

Test should not compile.

foo/Test.scala:6: error: not found: type B
  def b = new B(1)
              ^
1 error

note

If I compile all sources together the accessibility is checked correctly:

$ $HOME/Applications/scala-2.13.1/bin/scalac bar/B.scala  foo/Test.scala -d foo/classes
foo/Test.scala:6: error: not found: type B
  def b = new B(1)
              ^
one error found

keyword for search

visibility

[som-snytt]

Duplicates #8121 which also turns on an import and separate compilation.

Fix was scala/scala#8753

I thought there was a similar "qualified access" ticket, but maybe not. It deserves a regression test, since Lukas feared side effects of symbol forcing, but I don't think he necessarily anticipated that other checks would start to work correctly.

[eed3si9n]

@som-snytt Thanks for the pointers!

Here's a PR for tests - scala/scala#9453