Handle poly functions in functionArgsInfo

Author: natsukagami

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

@@ -506,10 +506,11 @@ class TypeApplications(val self: Type) extends AnyVal {
     case _ => Nil
 
   /** If this is an encoding of a function type, return its arguments, otherwise return Nil.
-   *  Handles ErasedFunctions gracefully.
+   *  Handles `ErasedFunction`s and poly functions gracefully.
    */
   final def functionArgInfos(using Context): List[Type] = self.dealias match
     case RefinedType(parent, nme.apply, mt: MethodType) if defn.isErasedFunctionType(parent) => (mt.paramInfos :+ mt.resultType)
+    case RefinedType(parent, nme.apply, mt: MethodType) if parent.typeSymbol eq defn.PolyFunctionClass => (mt.paramInfos :+ mt.resultType)
     case _ => self.dropDependentRefinement.dealias.argInfos
 
   /** Argument types where existential types in arguments are disallowed */