Names and definitions for Lambdas

Adding names and definitions for the Lambda scheme to hk types.
Also add HigherKinded flag for HK type parameters and abstract types.

1 files changed, 61 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/Definitions.scala b/src/dotty/tools/dotc/core/Definitions.scala
index 6f34efc8b..3f567d87a 100644
--- a/src/dotty/tools/dotc/core/Definitions.scala
+++ b/src/dotty/tools/dotc/core/Definitions.scala
@@ -422,7 +422,7 @@ class Definitions {
   def functionArity(tp: Type) = tp.dealias.argInfos.length - 1
 
   // ----- Higher kinds machinery ------------------------------------------
-
+  // tbr
   private var _hkTraits: Set[Symbol] = Set()
 
   /** The set of HigherKindedXYZ traits encountered so far */
@@ -476,6 +476,66 @@ class Definitions {
     hkTraitOfArity.getOrElseUpdate(vcs, createTrait)
   }
 
+  // ----- LambdaXYZ traits ------------------------------------------
+
+  private var myLambdaTraits: Set[Symbol] = Set()
+
+  /** The set of HigherKindedXYZ traits encountered so far */
+  def lambdaTraits: Set[Symbol] = myLambdaTraits
+
+  private var lambdaTraitForVariances = mutable.Map[List[Int], ClassSymbol]()
+
+  /** The HigherKinded trait corresponding to symbols `boundSyms` (which are assumed
+   *  to be the type parameters of a higher-kided type). This is a class symbol that
+   *  would be generated by the following schema.
+   *
+   *      class LambdaXYZ { type v_1 Arg1; ...; type v_N ArgN; type Apply }
+   *
+   *  Here:
+   *
+   *   - XYZ is a string of length N with one letter for each variant of a bound symbols,
+   *     using `P` (positive variance), `N` (negative variance), `I` (invariant).
+   *   - v_i are the variances of the bound symbols (i.e. +, -, or empty).
+   */
+  def lambdaTrait(vcs: List[Int]): ClassSymbol = {
+    assert(vcs.nonEmpty)
+
+    def varianceFlags(v: Int) = v match {
+      case -1 => Contravariant
+      case  0 => EmptyFlags
+      case  1 => Covariant
+    }
+
+    val completer = new LazyType  {
+      def complete(denot: SymDenotation)(implicit ctx: Context): Unit = {
+        val cls = denot.asClass.classSymbol
+        val paramDecls = newScope
+        for (i <- 0 until vcs.length)
+          newTypeParam(cls, tpnme.lambdaArgName(i), varianceFlags(vcs(i)), paramDecls)
+        newTypeParam(cls, tpnme.Apply, EmptyFlags, paramDecls)
+        val parentTraitRefs =
+          for (i <- 0 until vcs.length if vcs(i) != 0)
+          yield lambdaTrait(vcs.updated(i, 0)).typeRef
+        denot.info = ClassInfo(
+            ScalaPackageClass.thisType, cls, ObjectClass.typeRef :: parentTraitRefs.toList, paramDecls)
+      }
+    }
+
+    val traitName = tpnme.lambdaTraitName(vcs)
+
+    def createTrait = {
+      val cls = newClassSymbol(
+        ScalaPackageClass,
+        traitName,
+        Trait | Interface | Synthetic,
+        completer)
+      myLambdaTraits += cls
+      cls
+    }
+
+    lambdaTraitForVariances.getOrElseUpdate(vcs, createTrait)
+  }
+
   // ----- primitive value class machinery ------------------------------------------
 
   lazy val ScalaNumericValueClasses: collection.Set[Symbol] =  Set(