Simplify defn.FunctionOf.unapply (#18486)

Author: nicolasstucki

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

@@ -459,7 +459,7 @@ class CheckCaptures extends Recheck, SymTransformer:
  else if meth == defn.Caps_unsafeUnbox then
  mapArgUsing(_.forceBoxStatus(false))
  else if meth == defn.Caps_unsafeBoxFunArg then
- def forceBox(tp: Type): Type = tp match
+ def forceBox(tp: Type): Type = tp.strippedDealias match
  case defn.FunctionOf(paramtpe :: Nil, restpe, isContextual) =>
  defn.FunctionOf(paramtpe.forceBoxStatus(true) :: Nil, restpe, isContextual)
  case tp @ RefinedType(parent, rname, rinfo: MethodType) =>

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

@@ -1143,16 +1143,13 @@ class Definitions {
  else FunctionNOf(args, resultType, isContextual)
 
  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 isFunctionNType(ft) =>
+ Some(targs.init, targs.last, ft.typeSymbol.name.isContextFunction)
+ case _ =>
+ None
  }
  }
 

compiler/src/dotty/tools/dotc/transform/Recheck.scala

@@ -104,7 +104,7 @@ object Recheck:
  * - in function and method parameter types
  * - under annotations
  */
- def normalizeByName(tp: Type)(using Context): Type = tp match
+ def normalizeByName(tp: Type)(using Context): Type = tp.dealias match
  case tp: ExprType =>
  mapExprType(tp)
  case tp: PolyType =>

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

@@ -2003,10 +2003,7 @@ 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).dealias match
- case defn.FunctionNOf(args, _, _) => args.length
- case _ => -1
+ if formals.length > idx then defn.functionArity(formals(idx))
  else -1
 
  val numArgs = args.length