Make export forwarders retain Extension flag

Author: odersky

compiler/src/dotty/tools/dotc/core/Flags.scala

@@ -594,6 +594,9 @@ object Flags {
 
   final val ImplicitOrImpliedOrGivenTerm = ImplicitOrImpliedOrGiven.toTermFlags
 
+  /** Flags retained in export forwarders */
+  final val RetainedExportFlags = ImplicitOrImpliedOrGiven | Extension
+
   /** Assumed to be pure */
   final val StableOrErased: FlagSet = StableRealizable | Erased
 

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -988,7 +988,7 @@ class Namer { typer: Typer =>
                 val maybeStable = if (mbr.symbol.isStableMember) StableRealizable else EmptyFlags
                 ctx.newSymbol(
                   cls, alias,
-                  Exported | Method | Final | maybeStable | mbr.symbol.flags & ImplicitOrImpliedOrGiven,
+                  Exported | Method | Final | maybeStable | mbr.symbol.flags & RetainedExportFlags,
                   mbr.info.ensureMethodic,
                   coord = span)
               }

tests/run/exports.check

@@ -2,3 +2,6 @@ config
 printing
 scanning
 config
+printing
+scanning
+scanning

tests/run/exports.scala

@@ -12,6 +12,7 @@ object Test extends App {
 
   class Scanner {
     def scan() = println("scanning")
+    def (x: Any) scanned = scan()
   }
   object Scanner extends Scanner
 
@@ -29,6 +30,16 @@ object Test extends App {
   Copier.cfg
   Copier.config
   Copier.config2
+
+  def test() = {
+    import Copier._
+    print()
+    scanIt()
+    val x = config2
+    val y = cfg
+    1.scanned
+  }
+  test()
 }
 
 final class Foo {