Merge pull request #8828 from dotty-staging/fix-prune

Don't lose info in bounds when pruning

Author: abgruszecki

compiler/src/dotty/tools/dotc/config/Config.scala

@@ -15,13 +15,6 @@ object Config {
    */
   final val checkConstraintsNonCyclic = false
 
-  /** Make sure none of the bounds of a parameter in an OrderingConstraint
-   *  contains this parameter at its toplevel (i.e. as an operand of a
-   *  combination of &'s and |'s.). The check is performed each time a new bound
-   *  is added to the constraint.
-   */
-  final val checkConstraintsSeparated = false
-
   /** Check that each constraint resulting from a subtype test
    *  is satisfiable.
    */

compiler/src/dotty/tools/dotc/core/Constraint.scala

@@ -151,7 +151,7 @@ abstract class Constraint extends Showable {
   def & (other: Constraint, otherHasErrors: Boolean)(implicit ctx: Context): Constraint
 
   /** Check that no constrained parameter contains itself as a bound */
-  def checkNonCyclic()(implicit ctx: Context): Unit
+  def checkNonCyclic()(implicit ctx: Context): this.type
 
   /** Check that constraint only refers to TypeParamRefs bound by itself */
   def checkClosed()(implicit ctx: Context): Unit

compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala

@@ -155,8 +155,7 @@ final class ProperGadtConstraint private(
           else if (isUpper) addLess(symTvar.origin, boundTvar.origin)
           else addLess(boundTvar.origin, symTvar.origin)
         case bound =>
-          if (isUpper) addUpperBound(symTvar.origin, bound)
-          else addLowerBound(symTvar.origin, bound)
+          addBoundTransitively(symTvar.origin, bound, isUpper)
       }
     ).reporting({
       val descr = if (isUpper) "upper" else "lower"
@@ -271,7 +270,7 @@ final class ProperGadtConstraint private(
 
   // ---- Debug ------------------------------------------------------------
 
-  override def constr_println(msg: => String): Unit = gadtsConstr.println(msg)
+  override def constr = gadtsConstr
 
   override def toText(printer: Printer): Texts.Text = constraint.toText(printer)