Better fix: Fix parents of tuple classes

We inserted the :* class not in the correct place, so the linearizations
of Tuple1..Tuple22 were messed up.

Author: odersky

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

@@ -1620,11 +1620,11 @@ class Definitions {
 
   /** If `cls` is Tuple1..Tuple22, add the corresponding *: type as last parent to `parents` */
   def adjustForTuple(cls: ClassSymbol, tparams: List[TypeSymbol], parents: List[Type]): List[Type] = {
-    def syntheticParent(tparams: List[TypeSymbol]): Type =
-      if (tparams.isEmpty) TupleTypeRef
-      else TypeOps.nestedPairs(tparams.map(_.typeRef))
-    if (isTupleClass(cls)) parents :+ syntheticParent(tparams)
-    else parents
+    if !isTupleClass(cls) then parents
+    else if tparams.isEmpty then parents :+ TupleTypeRef
+    else
+      assert(parents.head.typeSymbol == ObjectClass)
+      TypeOps.nestedPairs(tparams.map(_.typeRef)) :: parents.tail
   }
 
   /** If it is BoxedUnit, remove `java.io.Serializable` from `parents`. */

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

@@ -349,11 +349,7 @@ object TypeOps:
       val doms = dominators(commonBaseClasses, Nil)
       def baseTp(cls: ClassSymbol): Type =
         tp.baseType(cls).mapReduceOr(identity)(mergeRefinedOrApplied)
-      def meet(tp1: Type, tp2: Type) =
-        if !tp1.exists then tp2
-        else if !tp2.exists then tp1
-        else AndType(tp1, tp2)
-      doms.map(baseTp).reduceLeft(meet)
+      doms.map(baseTp).reduceLeft(AndType.apply)
     }
 
     tp match {