Simplify defn.FunctionOf.unapply

Author: nicolasstucki

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

@@ -408,10 +408,9 @@ class CheckCaptures extends Recheck, SymTransformer:
       else if meth == defn.Caps_unsafeUnbox then
         mapArgUsing(_.forceBoxStatus(false))
       else if meth == defn.Caps_unsafeBoxFunArg then
-        mapArgUsing:
-          case defn.FunctionOf(paramtpe :: Nil, restpe, isContextual) =>
-            defn.FunctionOf(paramtpe.forceBoxStatus(true) :: Nil, restpe, isContextual)
-
+        mapArgUsing: tp =>
+          val defn.FunctionOf(paramtpe :: Nil, restpe, isContextual) = tp.strippedDealias: @unchecked
+          defn.FunctionOf(paramtpe.forceBoxStatus(true) :: Nil, restpe, isContextual)
       else
         super.recheckApply(tree, pt) match
           case appType @ CapturingType(appType1, refs) =>

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

@@ -1116,16 +1116,13 @@ class Definitions {
       else
         FunctionType(args.length, isContextual).appliedTo(args ::: resultType :: Nil)
     def unapply(ft: Type)(using Context): Option[(List[Type], Type, Boolean)] = {
-      ft.dealias match
+      ft match
         case PolyFunctionOf(mt: MethodType) =>
           Some(mt.paramInfos, mt.resType, mt.isContextualMethod)
-        case dft =>
-          val tsym = dft.typeSymbol
-          if isFunctionSymbol(tsym) && ft.isRef(tsym) then
-            val targs = dft.argInfos
-            if (targs.isEmpty) None
-            else Some(targs.init, targs.last, tsym.name.isContextFunction)
-          else None
+        case AppliedType(parent, targs) if targs.nonEmpty && isFunctionNType(ft) =>
+          Some(targs.init, targs.last, ft.typeSymbol.name.isContextFunction)
+        case _ =>
+          None
     }
   }
 

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

@@ -1990,10 +1990,7 @@ trait Applications extends Compatibility {
         // the arity of that function, otherise -1.
         def paramCount(ref: TermRef) =
           val formals = ref.widen.firstParamTypes
-          if formals.length > idx then
-            formals(idx) match
-              case defn.FunctionOf(args, _, _) => args.length
-              case _ => -1
+          if formals.length > idx then defn.functionArity(formals(idx))
           else -1
 
         val numArgs = args.length