From 8062bb5192c251f0ebced406a9575e03f65e6940 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Tue, 4 Jul 2023 15:00:30 +0200
Subject: [PATCH] Make toplevel protected qualified protected

For private toplevel definitions we expand `private` to `private[p]`
where `p` is the enclosing package. This PR applies the same scheme to
protected toplevel definitions.

Rationale: #18057 fixed an issue where toplevel protected members were always accessible
because explicit package object prefixes were added after the accessibility check was done,
and would re-establish the previous members without doing an accessibility check. The fix was
done by adding package objects first, then doing he rest of the checks. But that also means
that protected toplevel objects now get checked as members of their synthetic package object
instead of as members of their package. To avoid that we make the package explicit as qalifier.

Thsi shouls also make specs2 compile again.
---
 .../dotty/communitybuild/CommunityBuildTest.scala |  6 +-----
 compiler/src/dotty/tools/dotc/core/Flags.scala    |  1 +
 compiler/src/dotty/tools/dotc/typer/Namer.scala   |  7 +++----
 tests/pos/i18124/definition.scala                 | 15 +++++++++++++++
 tests/pos/i18124/usage.scala                      |  8 ++++++++
 5 files changed, 28 insertions(+), 9 deletions(-)
 create mode 100644 tests/pos/i18124/definition.scala
 create mode 100644 tests/pos/i18124/usage.scala

diff --git a/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala b/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
index 8837f7319117..bf6b6d431509 100644
--- a/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
+++ b/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
@@ -93,11 +93,7 @@ class CommunityBuildTestC:
   @Test def sconfig = projects.sconfig.run()
   @Test def shapeless = projects.shapeless.run()
   @Test def sourcecode = projects.sourcecode.run()
-
-  // Disabled. Currently fails in FutureMatchers.scala. The call to
-  // `checkResultFailure` goes to a protected method which is not accessible.
-  // I tried to fix it, but get test failures.
-  // @Test def specs2 = projects.specs2.run()
+  @Test def specs2 = projects.specs2.run()
 
   @Test def stdLib213 = projects.stdLib213.run()
   @Test def ujson = projects.ujson.run()
diff --git a/compiler/src/dotty/tools/dotc/core/Flags.scala b/compiler/src/dotty/tools/dotc/core/Flags.scala
index 8100bea374eb..62cb5726c6af 100644
--- a/compiler/src/dotty/tools/dotc/core/Flags.scala
+++ b/compiler/src/dotty/tools/dotc/core/Flags.scala
@@ -600,6 +600,7 @@ object Flags {
   val TermParamOrAccessor: FlagSet           = Param | ParamAccessor
   val PrivateParamAccessor: FlagSet          = ParamAccessor | Private
   val PrivateOrArtifact: FlagSet             = Private | Artifact
+  val PrivateOrProtected: FlagSet            = Private | Protected
   val ClassTypeParam: FlagSet                = Private | TypeParam
   val Scala2Trait: FlagSet                   = Scala2x | Trait
   val SyntheticArtifact: FlagSet             = Synthetic | Artifact
diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index 44787dcfeedc..9c67d1a11f73 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -223,11 +223,10 @@ class Namer { typer: Typer =>
       var flags1 = flags
       var privateWithin = privateWithinClass(tree.mods)
       val effectiveOwner = owner.skipWeakOwner
-      if (flags.is(Private) && effectiveOwner.is(Package)) {
-        // If effective owner is a package p, widen private to private[p]
-        flags1 = flags1 &~ PrivateLocal
+      if (flags.isOneOf(PrivateOrProtected) && !privateWithin.exists) && effectiveOwner.is(Package) then
+        // If effective owner is a package p, widen private to private[p] and protected to protected[p]
+        flags1 = flags1 &~ PrivateLocal // drop private but keep protected
         privateWithin = effectiveOwner
-      }
 
       val sym =
         if (prev.exists) {
diff --git a/tests/pos/i18124/definition.scala b/tests/pos/i18124/definition.scala
new file mode 100644
index 000000000000..1377c94fe7cd
--- /dev/null
+++ b/tests/pos/i18124/definition.scala
@@ -0,0 +1,15 @@
+// definition.scala
+package oolong.bson:
+
+  trait BsonValue
+  protected def merge(
+      base: BsonValue,
+      patch: BsonValue,
+      arraySubvalues: Boolean = false
+  ): BsonValue = ???
+
+  private def foo: Int = 1
+
+  package inner:
+    protected[bson] def bar = 2
+
diff --git a/tests/pos/i18124/usage.scala b/tests/pos/i18124/usage.scala
new file mode 100644
index 000000000000..0bc0417c01ad
--- /dev/null
+++ b/tests/pos/i18124/usage.scala
@@ -0,0 +1,8 @@
+// usage.scala
+package oolong.bson
+
+extension (bv: BsonValue)
+  def :+(other: BsonValue): BsonValue = merge(other, bv, false)
+
+val x = foo
+val y = inner.bar