From 171773d9d8067dc54028c54c0cc8257c9c06a1a8 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Wed, 30 Aug 2023 16:36:55 +0200
Subject: [PATCH] Simplify `defn.FunctionOf.unapply`

---
 .../src/dotty/tools/dotc/cc/CheckCaptures.scala     |  2 +-
 .../src/dotty/tools/dotc/core/Definitions.scala     | 13 +++++--------
 .../src/dotty/tools/dotc/transform/Recheck.scala    |  2 +-
 .../src/dotty/tools/dotc/typer/Applications.scala   |  5 +----
 4 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala b/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala
index a49bd9f79351..d6a03667311a 100644
--- a/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala
+++ b/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) =>
diff --git a/compiler/src/dotty/tools/dotc/core/Definitions.scala b/compiler/src/dotty/tools/dotc/core/Definitions.scala
index dd92687262de..070a71e8f671 100644
--- a/compiler/src/dotty/tools/dotc/core/Definitions.scala
+++ b/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
     }
   }
 
diff --git a/compiler/src/dotty/tools/dotc/transform/Recheck.scala b/compiler/src/dotty/tools/dotc/transform/Recheck.scala
index b15a58b98b6f..def0f1e1b98f 100644
--- a/compiler/src/dotty/tools/dotc/transform/Recheck.scala
+++ b/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 =>
diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 62cef94330c1..49c8910712c7 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/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