Add a run test for poly context bounds; cleanup typer changes

[Cherry-picked f9db9fa]

Author: KacperFKorban

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

@@ -22,7 +22,6 @@ import parsing.Parsers
 
 import scala.annotation.internal.sharable
 import scala.annotation.threadUnsafe
-import dotty.tools.dotc.quoted.QuoteUtils.treeOwner
 
 object desugar {
   import untpd.*

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1942,15 +1942,15 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           val resultTpt =
             untpd.InLambdaTypeTree(isResult = true, (tsyms, vsyms) =>
               mt.resultType.substParams(mt, vsyms.map(_.termRef)).substParams(poly, tsyms.map(_.typeRef)))
-          val desugared @ Block(List(defdef), _) = desugar.makeClosure(tparams, inferredVParams, body, resultTpt, tree.span)
+          val desugared = desugar.makeClosure(tparams, inferredVParams, body, resultTpt, tree.span)
           typed(desugared, pt)
         else
           val msg =
             em"""|Provided polymorphic function value doesn't match the expected type $dpt.
                  |Expected type should be a polymorphic function with the same number of type and value parameters."""
           errorTree(EmptyTree, msg, tree.srcPos)
       case _ =>
-        val desugared @ Block(List(defdef), _) = desugar.makeClosure(tparams, vparams, body, untpd.TypeTree(), tree.span)
+        val desugared = desugar.makeClosure(tparams, vparams, body, untpd.TypeTree(), tree.span)
         typed(desugared, pt)
   end typedPolyFunctionValue
 
@@ -3578,17 +3578,17 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
               case xtree => typedUnnamed(xtree)
 
           val unsimplifiedType = result.tpe
-          val result1 = simplify(result, pt, locked)
-          result1.tpe.stripTypeVar match
+          simplify(result, pt, locked)
+          result.tpe.stripTypeVar match
             case e: ErrorType if !unsimplifiedType.isErroneous => errorTree(xtree, e.msg, xtree.srcPos)
-            case _ => result1
+            case _ => result
         catch case ex: TypeError =>
           handleTypeError(ex)
      }
   }
 
   /** Interpolate and simplify the type of the given tree. */
-  protected def simplify(tree: Tree, pt: Type, locked: TypeVars)(using Context): Tree =
+  protected def simplify(tree: Tree, pt: Type, locked: TypeVars)(using Context): tree.type =
     if !tree.denot.isOverloaded then // for overloaded trees: resolve overloading before simplifying
       if !tree.tpe.widen.isInstanceOf[MethodOrPoly] // wait with simplifying until method is fully applied
          || tree.isDef                              // ... unless tree is a definition

tests/run/contextbounds-for-poly-functions.check

@@ -0,0 +1,6 @@
+42
+a string
+Kate is 27 years old
+42 and a string
+a string and Kate is 27 years old
+Kate is 27 years old and 42

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

@@ -0,0 +1,30 @@
+import scala.language.experimental.modularity
+import scala.language.future
+
+trait Show[X]:
+  def show(x: X): String
+
+given Show[Int] with
+  def show(x: Int) = x.toString
+
+given Show[String] with
+  def show(x: String) = x
+
+case class Person(name: String, age: Int)
+
+given Show[Person] with
+  def show(x: Person) = s"${x.name} is ${x.age} years old"
+
+type Shower = [X: Show] => X => String
+val shower: Shower = [X: {Show as show}] => (x: X) => show.show(x)
+
+type DoubleShower = [X: Show] => X => [Y: Show] => Y => String
+val doubleShower: DoubleShower = [X: {Show as show1}] => (x: X) => [Y: {Show as show2}] => (y: Y) => s"${show1.show(x)} and ${show2.show(y)}"
+
+object Test extends App:
+  println(shower(42))
+  println(shower("a string"))
+  println(shower(Person("Kate", 27)))
+  println(doubleShower(42)("a string"))
+  println(doubleShower("a string")(Person("Kate", 27)))
+  println(doubleShower(Person("Kate", 27))(42))