Avoid too precise type for TYPEREFsymbol; restore TestMonad

Author: bishabosha

README.md

@@ -13,6 +13,7 @@ There is a small set of test files in `/test/tasty/`, here is the procedure (to
   - Files matching `/test/tasty/src-2/Test*.scala` are designed to test that symbols from TASTy files are unpickled correctly, so depend on symbols that are defined in `/test/tasty/src-3/*`.
     - These are required to pass before they can be committed. (i.e. print "_Suite passed!_" when their main function is run.)
   - `/test/tasty/suspended/` are for dotty sources that have not yet been feature implemented.
+  - Some tests require the Dotty class library on the classpath, to obtain this, just use [coursier](https://get-coursier.io), for example like `scala -classpath out:$(coursier fetch -p ch.epfl.lamp:dotty-library_<VERSION>:<RELEASE>) tastytest.TestHello` to run the `TestHello` suite.
 
 # Welcome!
 

src/compiler/scala/tools/nsc/tasty/TreeUnpickler.scala

@@ -428,13 +428,12 @@ abstract class TreeUnpickler(reader: TastyReader,
     private def readSymNameRef()(implicit ctx: Context): Type = {
       val sym = readSymRef()
       val prefix = readType()
-      val res = typeRef(prefix, sym, Nil)
       prefix match {
         case prefix: ThisType if prefix.sym eq sym.owner /*&& !sym.is(Opaque)*/ =>
-          res //res.withDenot(sym.denot)
+          typeRef(NoPrefix, sym, Nil) //res.withDenot(sym.denot)
           // without this precaution we get an infinite cycle when unpickling pos/extmethods.scala
           // the problem arises when a self type of a trait is a type parameter of the same trait.
-        case _ => res
+        case _ => typeRef(prefix, sym, Nil)
       }
     }
 
@@ -796,7 +795,9 @@ abstract class TreeUnpickler(reader: TastyReader,
       val localCtx = localContext(sym)
       val noCycle  = tag match {
         case DEFDEF =>
-          assertTasty(!(completer.tastyFlagSet &~ Extension), s"unsupported flags on def: ${completer.tastyFlagSet.show}")
+          val (isExtension, exceptExtension) = completer.tastyFlagSet.except(Extension)
+          assertTasty(!exceptExtension, s"unsupported Scala 3 flags on def: ${exceptExtension.show}")
+          if (isExtension) ctx.log(s"$name is a Scala 3 extension method.")
           val tparams = readParams[NoCycle](TYPEPARAM)(localCtx)
           val vparamss = readParamss(localCtx)
           val tpt = readTpt()(localCtx)
@@ -814,7 +815,7 @@ abstract class TreeUnpickler(reader: TastyReader,
           sym.info = if (sym.flags.not(Module)) internal.nullaryMethodType(tpe) else tpe // TODO: really?
           NoCycle(at = symAddr)
         case TYPEDEF | TYPEPARAM =>
-          assertTasty(!completer.tastyFlagSet, s"unsupported flags on type: ${completer.tastyFlagSet.show}")
+          assertTasty(!completer.tastyFlagSet, s"unsupported Scala 3 flags on type: ${completer.tastyFlagSet.show}")
           if (sym.isClass) {
             sym.owner.ensureCompleted()
             readTemplate(symAddr)(localCtx)

test/tasty/src-2/tastytest/ConcreteError.scala

@@ -1,5 +1,7 @@
 package tastytest
 
+import scala.runtime.ScalaRunTime
+
 object TestEmpty {
 
   def test1 = assert(productString(new EmptyProduct) === "EmptyProduct()")

test/tasty/src-2/tastytest/TestEmpty.scala

@@ -1,12 +1,15 @@
 package tastytest
 
 object TestError {
-  def test1 = assert((try throw new ConcreteError catch handler) === "ConcreteError")
+
+  final class ConcreteError extends AbsError("ConcreteError")
 
   val handler: PartialFunction[Throwable, String] = {
     case e: ConcreteError => e.getMessage()
   }
 
+  def test1 = assert((try throw new ConcreteError catch handler) === "ConcreteError")
+
   def main(args: Array[String]): Unit = {
     test1
     println("Suite passed!")

test/tasty/src-2/tastytest/TestError.scala

@@ -1,16 +1,11 @@
 package tastytest
 
-object TestFunctor {
+object TestMonad {
 
   implicit object ListMonad extends Monad[List] {
-
-    def flatMap[A, B](fa: List[A])(f: A => List[B]): List[B] = fa.flatMap(f)
     def pure[A](x: A): List[A] = x :: Nil
-
-    // error: Missing implementation for:
-    //   def map[A, B](fa: Monad.this.F[A])(f: A => B): Monad.this.F[B] // inherited from trait Functor
+    def flatMap[A, B](fa: List[A])(f: A => List[B]): List[B] = fa.flatMap(f)
     override def map[A, B](fa: List[A])(f: A => B): List[B] = fa.map(f)
-
   }
 
   def pureToString[F[_], A](fa: F[A])(implicit F: Monad[F]): F[String] = F.flatMap(fa)(a => F.pure(a.toString))

test/tasty/suspended/tastytest/TestMonad.scala renamed to test/tasty/src-2/tastytest/TestMonad.scala

@@ -1,6 +1,4 @@
 package object tastytest {
-  import scala.runtime.ScalaRunTime
-
   implicit final class SafeEq[T](private val t: T) extends AnyVal {
     final def ===[U](u: U)(implicit ev: T =:= U): Boolean = t == u
   }