Fix existential mapping of non-dependent impure function aliases =>

There was a forgotten case.

Author: odersky

compiler/src/dotty/tools/dotc/cc/Existential.scala

@@ -315,6 +315,12 @@ object Existential:
         case t @ CapturingType(parent, refs: CaptureSet.Var) =>
           if variance > 0 then needsWrap = true
           super.mapOver(t)
+        case defn.FunctionNOf(args, res, contextual) if t.typeSymbol.name.isImpureFunction =>
+          if variance > 0 then
+            needsWrap = true
+            super.mapOver:
+              defn.FunctionNOf(args, res, contextual).capturing(boundVar.singletonCaptureSet)
+          else mapOver(t)
         case _ =>
           mapOver(t)
         //.showing(i"mapcap $t = $result")
@@ -341,6 +347,7 @@ object Existential:
         case res: MethodType => mapFunOrMethod(res, res.paramInfos, res.resType)
         case res: PolyType => mapFunOrMethod(res, Nil, res.resType) // TODO: Also map bounds of PolyTypes
         case _ => mapCap(apply(res), fail)
+          //.showing(i"map cap res $res / ${apply(res)} of $tp = $result")
       tp.derivedFunctionOrMethod(args1, res1)
 
     def apply(t: Type): Type = t match

tests/neg/existential-mapping.check

@@ -68,21 +68,21 @@
 -- [E007] Type Mismatch Error: tests/neg/existential-mapping.scala:36:25 -----------------------------------------------
 36 |  val _: A^ => C^ => C = y4 // error
    |                         ^^
-   |                         Found:    (y4 : A^ => C^ => (ex$52: caps.Exists) -> C^{ex$52})
-   |                         Required: A^ => C^ => C
+   |                   Found:    (y4 : A^ => (ex$53: caps.Exists) -> C^ ->{ex$53} (ex$52: caps.Exists) -> C^{ex$52})
+   |                   Required: A^ => (ex$56: caps.Exists) -> C^ ->{ex$56} C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg/existential-mapping.scala:39:30 -----------------------------------------------
 39 |  val _: A^ => (x: C^) -> C = y5 // error
    |                              ^^
-   |                              Found:    (y5 : A^ => (ex$60: caps.Exists) -> Fun[C^{ex$60}])
+   |                              Found:    (y5 : A^ => (ex$58: caps.Exists) -> Fun[C^{ex$58}])
    |                              Required: A^ => (x: C^) -> C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg/existential-mapping.scala:42:30 -----------------------------------------------
 42 |  val _: A^ => (x: C^) => C = y6 // error
    |                              ^^
-   |                              Found:    (y6 : A^ => (ex$66: caps.Exists) -> IFun[C^{ex$66}])
-   |                              Required: A^ => (ex$69: caps.Exists) -> (x: C^) ->{ex$69} C
+   |                              Found:    (y6 : A^ => (ex$64: caps.Exists) -> IFun[C^{ex$64}])
+   |                              Required: A^ => (ex$67: caps.Exists) -> (x: C^) ->{ex$67} C
    |
    | longer explanation available when compiling with `-explain`

tests/neg/existential-mapping.scala

@@ -44,4 +44,3 @@ def Test =
   val z1: A^ => Array[C^] = ??? // error
 
 
-