Make toplevel privates package private

This is the only way that avoids tricky special cases.

Also: Fix desugaring of toplevel definitions so that imports are
visible in wrapper objects.

Author: odersky

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1047,8 +1047,14 @@ object desugar {
     else {
       val sourceName = ctx.source.file.name.takeWhile(_ != '.')
       val groupName = (sourceName ++ str.TOPLEVEL_SUFFIX).toTermName
-      val grouped = ModuleDef(groupName, Template(emptyConstructor, Nil, Nil, EmptyValDef, nestedStats))
-      cpy.PackageDef(pdef)(pdef.pid, grouped :: topStats)
+      val widenedStats = nestedStats.map {
+        case stat: MemberDef if stat.mods.is(Private) =>
+          stat.withMods((stat.mods &~ Private).withPrivateWithin(pdef.pid.name.toTypeName))
+        case stat =>
+          stat
+      }
+      val grouped = ModuleDef(groupName, Template(emptyConstructor, Nil, Nil, EmptyValDef, widenedStats))
+      cpy.PackageDef(pdef)(pdef.pid, topStats :+ grouped)
     }
   }
 

docs/docs/reference/dropped-features/package-objects.md

@@ -41,19 +41,4 @@ If a source file `src.scala` contains such toplevel definitions, they will be pu
 in a source file `src.scala`, it could be invoked from the command line using a command like `scala src$package`. Since the
 "program name" is mangled it is recommended to always put `main` methods in explicitly named objects.
 
-### Private toplevel definitions
-
-If a private toplevel definition is wrapped in a synthetic object, it is visible only
-in definitions in the same source file. By contrast, a package-private definition is visible in the whole containing package. Example:
-
-```scala
-// file 1:
-package p
-private val x = 1
-private[p] val y = 2
-
-// file 2:
-package p
-val xx = x  // error: not found: x
-val yy = y  // ok
-```
+**Note 3:** The notion of `private` is independent of whether a definition is wrapped or not. A `private` toplevel definition is always visible from everywhere in the enclosing package.

tests/neg/toplevel-privates/A.scala

@@ -1,11 +1,14 @@
-package p
+package p22
 
 private val x = 10
 
 val y = x
 
-private[p] val xx = 10
+private[p22] val xx = 10
 
 val yy = xx
 
-private class C
+private class C {
+  val z = x
+}
+

tests/neg/toplevel-privates/Test.scala

@@ -1,11 +1,13 @@
-package p
+package q
 
-val x1 = x    // error
+import p._
+
+val x1 = x    // error: not found
 
 val y1 = y    // ok
 
-val xx1 = xx  // ok
+val xx1 = xx  // error: not found
 
 val yy1 = yy  // ok
 
-val c = new C // ok
+val c = new C // error: not found

tests/pos/toplevel-privates/A.scala

@@ -0,0 +1,14 @@
+package p
+
+private val x = 10
+
+val y = x
+
+private[p] val xx = 10
+
+val yy = xx
+
+private class C {
+  val z = x
+}
+

tests/pos/toplevel-privates/Test.scala

@@ -0,0 +1,11 @@
+package p
+
+val x1 = x
+
+val y1 = y
+
+val xx1 = xx
+
+val yy1 = yy
+
+val c = new C