Fix scala#10143: Handle shared package references

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/tasty/TastyClassName.scala

@@ -25,18 +25,14 @@ class TastyClassName(bytes: Array[Byte]) {
     import dotty.tools.tasty.TastyFormat._
     def unpickle(reader: TastyReader, tastyName: NameTable): (TermName, TermName) = {
       import reader._
-      def readName() = {
-        val idx = readNat()
-        nameAtRef(NameRef(idx))
-      }
       def readNames(packageName: TermName): (TermName, TermName) = {
         val tag = readByte()
         if (tag >= firstLengthTreeTag) {
           val len = readNat()
           val end = currentAddr + len
           tag match {
             case TYPEDEF =>
-              val className = readName()
+              val className = reader.readName()
               goto(end)
               (packageName, className)
             case IMPORT | VALDEF =>
@@ -48,13 +44,26 @@ class TastyClassName(bytes: Array[Byte]) {
         }
         else tag match {
           case TERMREFpkg | TYPEREFpkg =>
-            val subPackageName = readName()
+            val subPackageName = reader.readName()
+            readNames(subPackageName)
+          case SHAREDtype =>
+            val addr = reader.readAddr()
+            val reader2 = reader.subReader(addr, reader.endAddr)
+            val tag2 = reader2.readByte()
+            assert(tag2 == TERMREFpkg || tag2 == TYPEREFpkg)
+            val subPackageName = reader2.readName()
             readNames(subPackageName)
           case _ =>
             readNames(packageName)
         }
       }
       readNames(nme.EMPTY_PACKAGE)
     }
+
+    extension (reader: TastyReader) def readName() = {
+      val idx = reader.readNat()
+      nameAtRef(NameRef(idx))
+    }
   }
+
 }