SI-8868 Fix unpickling of local dummy symbols

These pop up as the owner of symbols in annotation arguments,
such as the ones introduced by the names/defaults desugaring.

The first two test cases here motivate the two patches to Unpicker.

The third requires both fixes, but exploits the problem directly,
without using `@deprecated` and named arguments.

See also 14fa7be / SI-8708 for a recently remedied kindred bug.

7 files changed, 34 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/pickling/UnPickler.scala b/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
index 8d4c3f752f..5433bfad60 100644
--- a/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
+++ b/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
@@ -243,8 +243,14 @@ abstract class UnPickler {
            } getOrElse "")
         }
 
+        def localDummy = {
+          if (nme.isLocalDummyName(name))
+            owner.newLocalDummy(NoPosition)
+          else NoSymbol
+        }
+
         // (1) Try name.
-        fromName(name) orElse {
+        localDummy orElse fromName(name) orElse {
           // (2) Try with expanded name.  Can happen if references to private
           // symbols are read from outside: for instance when checking the children
           // of a class.  See #1722.
@@ -298,6 +304,7 @@ abstract class UnPickler {
          * (.) ...
          * (1) `local child` represents local child classes, see comment in Pickler.putSymbol.
          *     Since it is not a member, it should not be entered in the owner's scope.
+         * (2) Similarly, we ignore local dummy symbols, as seen in SI-8868
          */
         def shouldEnterInOwnerScope = {
           sym.owner.isClass &&
@@ -307,7 +314,8 @@ abstract class UnPickler {
             !sym.isRefinementClass &&
             !sym.isTypeParameter &&
             !sym.isExistentiallyBound &&
-            sym.rawname != tpnme.LOCAL_CHILD // (1)
+            sym.rawname != tpnme.LOCAL_CHILD && // (1)
+            !nme.isLocalDummyName(sym.rawname)  // (2)
         }
 
         markFlagsCompleted(sym)(mask = AllFlags)
diff --git a/test/files/pos/t8868a/Sub_2.scala b/test/files/pos/t8868a/Sub_2.scala
new file mode 100644
index 0000000000..a19b529c88
--- /dev/null
+++ b/test/files/pos/t8868a/Sub_2.scala
@@ -0,0 +1 @@
+class Sub extends T
diff --git a/test/files/pos/t8868a/T_1.scala b/test/files/pos/t8868a/T_1.scala
new file mode 100644
index 0000000000..9fb97b1413
--- /dev/null
+++ b/test/files/pos/t8868a/T_1.scala
@@ -0,0 +1,6 @@
+class C
+
+trait T {
+  @deprecated(since = "", message = "")
+  class X
+}
diff --git a/test/files/pos/t8868b/Sub_2.scala b/test/files/pos/t8868b/Sub_2.scala
new file mode 100644
index 0000000000..58b44db2b3
--- /dev/null
+++ b/test/files/pos/t8868b/Sub_2.scala
@@ -0,0 +1,2 @@
+class Sub extends T
+
diff --git a/test/files/pos/t8868b/T_1.scala b/test/files/pos/t8868b/T_1.scala
new file mode 100644
index 0000000000..0b71cfdaa3
--- /dev/null
+++ b/test/files/pos/t8868b/T_1.scala
@@ -0,0 +1,4 @@
+@deprecated(since = "2.4.0", message = "")
+trait T {
+  class X
+}
diff --git a/test/files/pos/t8868c/Sub_2.scala b/test/files/pos/t8868c/Sub_2.scala
new file mode 100644
index 0000000000..58b44db2b3
--- /dev/null
+++ b/test/files/pos/t8868c/Sub_2.scala
@@ -0,0 +1,2 @@
+class Sub extends T
+
diff --git a/test/files/pos/t8868c/T_1.scala b/test/files/pos/t8868c/T_1.scala
new file mode 100644
index 0000000000..dc541950d8
--- /dev/null
+++ b/test/files/pos/t8868c/T_1.scala
@@ -0,0 +1,9 @@
+class C(a: Any) extends annotation.StaticAnnotation
+
+@C({val x = 0; x})
+trait T {
+  class X
+
+  @C({val x = 0; x})
+  def foo = 42
+}