Fix pickling issue

Author: KacperFKorban

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1228,7 +1228,7 @@ object desugar {
     val PolyFunction(tparams: List[untpd.TypeDef] @unchecked, fun @ Function(vparamTypes, res)) = tree: @unchecked
     val newTParams = tparams.mapConserve {
       case td @ TypeDef(name, cb @ ContextBounds(bounds, ctxBounds)) =>
-        TypeDef(name, ContextBounds(bounds, List.empty))
+        cpy.TypeDef(td)(name, bounds)
       case t => t
     }
     var idx = 0

tests/pos/contextbounds-for-poly-functions.scala

@@ -5,10 +5,11 @@ import scala.language.future
 trait Ord[X]:
   def compare(x: X, y: X): Int
 
-// val less1 = [X: Ord] => (x: X, y: X) => summon[Ord[X]].compare(x, y) < 0
+val less1 = [X: Ord] => (x: X, y: X) => summon[Ord[X]].compare(x, y) < 0
 
-// val less2 = [X: Ord as ord] => (x: X, y: X) => ord.compare(x, y) < 0
+val less2 = [X: Ord as ord] => (x: X, y: X) => ord.compare(x, y) < 0
 
+type CtxFunctionRef = Ord[Int] ?=> Boolean
 type ComparerRef = [X] => (x: X, y: X) => Ord[X] ?=> Boolean
 type Comparer = [X: Ord] => (x: X, y: X) => Boolean
 val less3: Comparer = [X: Ord as ord] => (x: X, y: X) => ord.compare(x, y) < 0