Make isFunctionType no longer recognize ErasedFunction refinements

Author: natsukagami

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

@@ -754,7 +754,7 @@ class CheckCaptures extends Recheck, SymTransformer:
               val (parent1, leaked) = adaptFun(parent, args.init, args.last, expected, covariant, insertBox,
                   (aargs1, ares1) => actual.derivedAppliedType(tycon, aargs1 :+ ares1))
               (parent1, leaked ++ cs)
-            case actual @ RefinedType(_, _, rinfo: MethodType) if defn.isFunctionType(actual) =>
+            case actual @ RefinedType(_, _, rinfo: MethodType) if defn.isFunctionOrPolyType(actual) =>
               // TODO Find a way to combine handling of generic and dependent function types (here and elsewhere)
               val (parent1, leaked) = adaptFun(parent, rinfo.paramInfos, rinfo.resType, expected, covariant, insertBox,
                 (aargs1, ares1) =>
@@ -973,7 +973,7 @@ class CheckCaptures extends Recheck, SymTransformer:
             case CapturingType(parent, refs) =>
               healCaptureSet(refs)
               traverse(parent)
-            case tp @ RefinedType(parent, rname, rinfo: MethodType) if defn.isFunctionType(tp) =>
+            case tp @ RefinedType(parent, rname, rinfo: MethodType) if defn.isFunctionOrPolyType(tp) =>
               traverse(rinfo)
             case tp: TermLambda =>
               val saved = allowed

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

@@ -54,7 +54,7 @@ extends tpd.TreeTraverser:
         val boxedRes = recur(res)
         if boxedRes eq res then tp
         else tp1.derivedAppliedType(tycon, args.init :+ boxedRes)
-      case tp1 @ RefinedType(_, _, rinfo) if defn.isFunctionType(tp1) =>
+      case tp1 @ RefinedType(_, _, rinfo: MethodType) if defn.isFunctionOrPolyType(tp1) =>
         val boxedRinfo = recur(rinfo)
         if boxedRinfo eq rinfo then tp
         else boxedRinfo.toFunctionType(isJava = false, alwaysDependent = true)
@@ -231,7 +231,7 @@ extends tpd.TreeTraverser:
                 tp.derivedAppliedType(tycon1, args1 :+ res1)
           else
             tp.derivedAppliedType(tycon1, args.mapConserve(arg => this(arg)))
-        case tp @ RefinedType(core, rname, rinfo) if defn.isFunctionType(tp) =>
+        case tp @ RefinedType(core, rname, rinfo: MethodType) if defn.isFunctionOrPolyType(tp) =>
           val rinfo1 = apply(rinfo)
           if rinfo1 ne rinfo then rinfo1.toFunctionType(isJava = false, alwaysDependent = true)
           else tp
@@ -327,7 +327,7 @@ extends tpd.TreeTraverser:
               args.last, CaptureSet.empty, currentCs ++ outerCs)
             tp.derivedAppliedType(tycon1, args1 :+ resType1)
         tp1.capturing(outerCs)
-      case tp @ RefinedType(parent, nme.apply, rinfo: MethodType) if defn.isFunctionType(tp) =>
+      case tp @ RefinedType(parent, nme.apply, rinfo: MethodType) if defn.isFunctionOrPolyType(tp) =>
         propagateDepFunctionResult(mapOver(tp), currentCs ++ outerCs)
           .capturing(outerCs)
       case _ =>

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

@@ -1671,10 +1671,14 @@ class Definitions {
 
   /** Is `tp` a representation of a (possibly dependent) function type or an alias of such? */
   def isFunctionType(tp: Type)(using Context): Boolean =
-    isNonRefinedFunction(tp.dropDependentRefinement) || isErasedFunctionType(tp)
+    isNonRefinedFunction(tp.dropDependentRefinement)
+
+  /** Is `tp` a specialized, refined function type? Either an `ErasedFunction` or a `PolyFunction`. */
+  def isRefinedFunctionType(tp: Type)(using Context): Boolean =
+    (tp.typeSymbol eq defn.PolyFunctionClass) || isErasedFunctionType(tp)
 
   def isFunctionOrPolyType(tp: Type)(using Context): Boolean =
-    isFunctionType(tp) || (tp.typeSymbol eq defn.PolyFunctionClass)
+    isFunctionType(tp) || isRefinedFunctionType(tp)
 
   private def withSpecMethods(cls: ClassSymbol, bases: List[Name], paramTypes: Set[TypeRef]) =
     for base <- bases; tp <- paramTypes do