Introduce recursive types

Map self-references in refinements to recursive types. This
commit does this for refinement types appearing in source.
We still have to do it for unpickled refinements.

Test apply-equiv got moved to pending because it simulates
the old higher-kinded type encoding in source, which relies
on the old representation in terms of self-referential refinement
types. The plan is not to adapt this encoding to the new
representation, but to replace it with a different encoding
that makes critical use of the added power of recursive types.

Use recursive types also when unpickling from Scala 2.x.

Add mapInfo method to Denotations.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/Denotations.scala b/src/dotty/tools/dotc/core/Denotations.scala
index 5ce8cbcd8..494df7547 100644
--- a/src/dotty/tools/dotc/core/Denotations.scala
+++ b/src/dotty/tools/dotc/core/Denotations.scala
@@ -146,6 +146,9 @@ object Denotations {
     /** Is this denotation different from NoDenotation or an ErrorDenotation? */
     def exists: Boolean = true
 
+    /** A denotation with the info of this denotation transformed using `f` */
+    def mapInfo(f: Type => Type)(implicit ctx: Context): Denotation
+
     /** If this denotation does not exist, fallback to alternative */
     final def orElse(that: => Denotation) = if (this.exists) this else that
 
@@ -242,7 +245,7 @@ object Denotations {
       }
       else if (exists && !qualifies(symbol)) NoDenotation
       else asSingleDenotation
-     }
+    }
 
     /** Form a denotation by conjoining with denotation `that`.
      *
@@ -456,6 +459,8 @@ object Denotations {
       else if (!d2.exists) d1
       else derivedMultiDenotation(d1, d2)
     }
+    def mapInfo(f: Type => Type)(implicit ctx: Context): Denotation =
+      derivedMultiDenotation(denot1.mapInfo(f), denot2.mapInfo(f))
     def derivedMultiDenotation(d1: Denotation, d2: Denotation) =
       if ((d1 eq denot1) && (d2 eq denot2)) this else MultiDenotation(d1, d2)
     override def toString = alternatives.mkString(" <and> ")
@@ -488,6 +493,9 @@ object Denotations {
       if ((symbol eq this.symbol) && (info eq this.info)) this
       else newLikeThis(symbol, info)
 
+    def mapInfo(f: Type => Type)(implicit ctx: Context): SingleDenotation =
+      derivedSingleDenotation(symbol, f(info))
+
     def orElse(that: => SingleDenotation) = if (this.exists) this else that
 
     def altsWith(p: Symbol => Boolean): List[SingleDenotation] =