Implementation of match/case def including GADT pattern matching.

1 files changed, 27 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/core/Symbols.scala b/src/dotty/tools/dotc/core/Symbols.scala
index 634be7cb7..6edc5c973 100644
--- a/src/dotty/tools/dotc/core/Symbols.scala
+++ b/src/dotty/tools/dotc/core/Symbols.scala
@@ -382,6 +382,33 @@ object Symbols {
      */
     def pos: Position = if (coord.isPosition) coord.toPosition else NoPosition
 
+// -------- GADT handling -----------------------------------------------
+
+    /** Perform given operation `op` where this symbol allows tightening of
+     *  its type bounds.
+     */
+    private[dotc] def withGADTFlexType[T](op: () => T)(implicit ctx: Context): () => T = { () =>
+      assert((denot is TypeParam) && denot.owner.isTerm)
+      val saved = denot
+      denot = denot.copySymDenotation(initFlags = denot.flags | GADTFlexType)
+      try op()
+      finally denot = saved
+    }
+
+    /** Disallow tightening of type bounds for this symbol from now on */
+    private[dotc] def resetGADTFlexType()(implicit ctx: Context): Unit = {
+      assert(denot is GADTFlexType)
+      denot = denot.copySymDenotation(initFlags = denot.flags &~ GADTFlexType)
+    }
+
+    /** Change info of this symbol to new, tightened type bounds */
+    private[core] def changeGADTInfo(bounds: TypeBounds)(implicit ctx: Context): Unit = {
+      assert(denot is GADTFlexType)
+      denot = denot.copySymDenotation(info = bounds)
+    }
+
+// -------- Printing --------------------------------------------------------
+
     /** The prefix string to be used when displaying this symbol without denotation */
     protected def prefixString = "Symbol"