Remove replace is{Poly|Erased}FunctionType with PolyOrErasedFunctionOf

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -954,6 +954,8 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
   def isStructuralTermSelectOrApply(tree: Tree)(using Context): Boolean = {
     def isStructuralTermSelect(tree: Select) =
       def hasRefinement(qualtpe: Type): Boolean = qualtpe.dealias match
+        case defn.PolyOrErasedFunctionOf(_) =>
+          false
         case RefinedType(parent, rname, rinfo) =>
           rname == tree.name || hasRefinement(parent)
         case tp: TypeProxy =>
@@ -966,10 +968,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
           false
       !tree.symbol.exists
       && tree.isTerm
-      && {
-        val qualType = tree.qualifier.tpe
-        hasRefinement(qualType) && !defn.isPolyOrErasedFunctionType(qualType)
-      }
+      && hasRefinement(tree.qualifier.tpe)
     def loop(tree: Tree): Boolean = tree match
       case TypeApply(fun, _) =>
         loop(fun)

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

@@ -1114,7 +1114,7 @@ class Definitions {
         FunctionType(args.length, isContextual).appliedTo(args ::: resultType :: Nil)
     def unapply(ft: Type)(using Context): Option[(List[Type], Type, Boolean)] = {
       ft.dealias match
-        case RefinedType(parent, nme.apply, mt: MethodType) if isErasedFunctionType(parent) =>
+        case PolyOrErasedFunctionOf(mt: MethodType) =>
           Some(mt.paramInfos, mt.resType, mt.isContextualMethod)
         case _ =>
           val tsym = ft.dealias.typeSymbol
@@ -1126,6 +1126,18 @@ class Definitions {
     }
   }
 
+  object PolyOrErasedFunctionOf {
+    /** Matches a refined `PolyFunction` or `ErasedFunction` type and extracts the apply info.
+     *
+     *  Pattern: `(PolyFunction | ErasedFunction) { def apply: $mt }`
+     */
+    def unapply(ft: Type)(using Context): Option[MethodicType] = ft.dealias match
+      case RefinedType(parent, nme.apply, mt: MethodicType)
+      if parent.derivesFrom(defn.PolyFunctionClass) || parent.derivesFrom(defn.ErasedFunctionClass) =>
+        Some(mt)
+      case _ => None
+  }
+
   object PartialFunctionOf {
     def apply(arg: Type, result: Type)(using Context): Type =
       PartialFunctionClass.typeRef.appliedTo(arg :: result :: Nil)
@@ -1713,26 +1725,16 @@ class Definitions {
   def isFunctionNType(tp: Type)(using Context): Boolean =
     isNonRefinedFunction(tp.dropDependentRefinement)
 
-  /** Does `tp` derive from `PolyFunction` or `ErasedFunction`? */
-  def isPolyOrErasedFunctionType(tp: Type)(using Context): Boolean =
-    isPolyFunctionType(tp) || isErasedFunctionType(tp)
-
-  /** Does `tp` derive from `PolyFunction`? */
-  def isPolyFunctionType(tp: Type)(using Context): Boolean =
-    tp.derivesFrom(defn.PolyFunctionClass)
-
-  /** Does `tp` derive from `ErasedFunction`? */
-  def isErasedFunctionType(tp: Type)(using Context): Boolean =
-    tp.derivesFrom(defn.ErasedFunctionClass)
-
   /** Returns whether `tp` is an instance or a refined instance of:
    *  - scala.FunctionN
    *  - scala.ContextFunctionN
    *  - ErasedFunction
    *  - PolyFunction
    */
   def isFunctionType(tp: Type)(using Context): Boolean =
-    isFunctionNType(tp) || isPolyOrErasedFunctionType(tp)
+    isFunctionNType(tp)
+    || tp.derivesFrom(defn.PolyFunctionClass)   // TODO check for refinement?
+    || tp.derivesFrom(defn.ErasedFunctionClass) // TODO check for refinement?
 
   private def withSpecMethods(cls: ClassSymbol, bases: List[Name], paramTypes: Set[TypeRef]) =
     if !ctx.settings.Yscala2Stdlib.value then
@@ -1836,7 +1838,7 @@ class Definitions {
     tp.stripTypeVar.dealias match
       case tp1: TypeParamRef if ctx.typerState.constraint.contains(tp1) =>
         asContextFunctionType(TypeComparer.bounds(tp1).hiBound)
-      case tp1 @ RefinedType(parent, nme.apply, mt: MethodType) if isErasedFunctionType(parent) && mt.isContextualMethod =>
+      case tp1 @ PolyOrErasedFunctionOf(mt: MethodType) if mt.isContextualMethod =>
         tp1
       case tp1 =>
         if tp1.typeSymbol.name.isContextFunction && isFunctionNType(tp1) then tp1
@@ -1856,7 +1858,7 @@ class Definitions {
         atPhase(erasurePhase)(unapply(tp))
       else
         asContextFunctionType(tp) match
-          case RefinedType(parent, nme.apply, mt: MethodType) if isErasedFunctionType(parent) =>
+          case PolyOrErasedFunctionOf(mt: MethodType) =>
             Some((mt.paramInfos, mt.resType, mt.erasedParams))
           case tp1 if tp1.exists =>
             val args = tp1.functionArgInfos

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

@@ -509,7 +509,7 @@ class TypeApplications(val self: Type) extends AnyVal {
    *  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.isPolyOrErasedFunctionType(parent) => (mt.paramInfos :+ mt.resultType)
+    case defn.PolyOrErasedFunctionOf(mt: MethodType) => (mt.paramInfos :+ mt.resultType)
     case _ => self.dropDependentRefinement.dealias.argInfos
 
   /** Argument types where existential types in arguments are disallowed */

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

@@ -666,7 +666,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
                 isSubType(info1, info2)
 
             if defn.isFunctionType(tp2) then
-              if defn.isPolyFunctionType(tp2) then
+              if tp2.derivesFrom(defn.PolyFunctionClass) then
                 // TODO should we handle ErasedFunction is this same way?
                 tp1.member(nme.apply).info match
                   case info1: PolyType =>

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

@@ -654,8 +654,8 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
         else SuperType(eThis, eSuper)
       case ExprType(rt) =>
         defn.FunctionType(0)
-      case RefinedType(parent, nme.apply, refinedInfo) if defn.isPolyOrErasedFunctionType(parent) =>
-        eraseRefinedFunctionApply(refinedInfo)
+      case defn.PolyOrErasedFunctionOf(mt) =>
+        eraseRefinedFunctionApply(mt)
       case tp: TypeVar if !tp.isInstantiated =>
         assert(inSigName, i"Cannot erase uninstantiated type variable $tp")
         WildcardType
@@ -936,7 +936,7 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
         sigName(defn.FunctionOf(Nil, rt))
       case tp: TypeVar if !tp.isInstantiated =>
         tpnme.Uninstantiated
-      case tp @ RefinedType(parent, nme.apply, _) if defn.isPolyOrErasedFunctionType(parent) =>
+      case tp @ defn.PolyOrErasedFunctionOf(_) =>
         // we need this case rather than falling through to the default
         // because RefinedTypes <: TypeProxy and it would be caught by
         // the case immediately below

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

@@ -1749,7 +1749,7 @@ object Types {
         else NoType
       case t if defn.isNonRefinedFunction(t) =>
         t
-      case t if defn.isErasedFunctionType(t) =>
+      case t @ defn.PolyOrErasedFunctionOf(_: MethodType) =>
         t
       case t @ SAMType(_) =>
         t

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

@@ -679,7 +679,7 @@ object Erasure {
           // Instead, we manually lookup the type of `apply` in the qualifier.
           inContext(preErasureCtx) {
             val qualTp = tree.qualifier.typeOpt.widen
-            if defn.isPolyOrErasedFunctionType(qualTp) then
+            if qualTp.derivesFrom(defn.PolyFunctionClass) || qualTp.derivesFrom(defn.ErasedFunctionClass) then
               eraseRefinedFunctionApply(qualTp.select(nme.apply).widen).classSymbol
             else
               NoSymbol

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

@@ -447,7 +447,12 @@ object TreeChecker {
       val tpe = tree.typeOpt
 
       // PolyFunction and ErasedFunction apply methods stay structural until Erasure
-      val isRefinedFunctionApply = (tree.name eq nme.apply) && defn.isPolyOrErasedFunctionType(tree.qualifier.typeOpt)
+      val isRefinedFunctionApply = (tree.name eq nme.apply) && {
+        tree.qualifier.typeOpt.widen match
+          case defn.PolyOrErasedFunctionOf(_) => true
+          case _ => false
+      }
+
       // Outer selects are pickled specially so don't require a symbol
       val isOuterSelect = tree.name.is(OuterSelectName)
       val isPrimitiveArrayOp = ctx.erasedTypes && nme.isPrimitiveName(tree.name)

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

@@ -105,7 +105,7 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
           expected =:= defn.FunctionOf(actualArgs, actualRet,
             defn.isContextFunctionType(baseFun))
         val arity: Int =
-          if defn.isErasedFunctionType(fun) then -1 // TODO support?
+          if fun.derivesFrom(defn.ErasedFunctionClass) then -1 // TODO support?
           else if defn.isFunctionNType(fun) then
             // TupledFunction[(...) => R, ?]
             fun.functionArgInfos match

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

@@ -1326,7 +1326,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
 
           (pt1.argInfos.init, typeTree(interpolateWildcards(pt1.argInfos.last.hiBound)))
         case RefinedType(parent, nme.apply, mt @ MethodTpe(_, formals, restpe))
-        if (defn.isNonRefinedFunction(parent) || defn.isErasedFunctionType(parent)) && formals.length == defaultArity =>
+        if defn.isNonRefinedFunction(parent) && formals.length == defaultArity =>
+          (formals, untpd.InLambdaTypeTree(isResult = true, (_, syms) => restpe.substParams(mt, syms.map(_.termRef))))
+        case defn.PolyOrErasedFunctionOf(mt @ MethodTpe(_, formals, restpe)) if formals.length == defaultArity =>
           (formals, untpd.InLambdaTypeTree(isResult = true, (_, syms) => restpe.substParams(mt, syms.map(_.termRef))))
         case pt1 @ SAMType(mt @ MethodTpe(_, formals, _)) =>
           val restpe = mt.resultType match