Add defn.RefinedFunctionOf extractor (#18432)

Part of #18305

Author: odersky

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

@@ -876,9 +876,8 @@ object CaptureSet:
           empty
         case CapturingType(parent, refs) =>
           recur(parent) ++ refs
-        case tpd @ RefinedType(parent, _, rinfo: MethodType)
-        if followResult && defn.isFunctionNType(tpd) =>
-          ofType(parent, followResult = false)                 // pick up capture set from parent type
+        case tpd @ defn.RefinedFunctionOf(rinfo: MethodType) if followResult =>
+          ofType(tpd.parent, followResult = false)             // pick up capture set from parent type
           ++ (recur(rinfo.resType)                             // add capture set of result
           -- CaptureSet(rinfo.paramRefs.filter(_.isTracked)*)) // but disregard bound parameters
         case tpd @ AppliedType(tycon, args) =>

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

@@ -195,7 +195,7 @@ class CheckCaptures extends Recheck, SymTransformer:
               capt.println(i"solving $t")
               refs.solve()
             traverse(parent)
-          case t @ RefinedType(_, nme.apply, rinfo) if defn.isFunctionType(t) =>
+          case t @ defn.RefinedFunctionOf(rinfo) =>
             traverse(rinfo)
           case tp: TypeVar =>
           case tp: TypeRef =>
@@ -302,8 +302,8 @@ class CheckCaptures extends Recheck, SymTransformer:
             t
           case _ =>
             val t1  = t match
-              case t @ RefinedType(parent, rname, rinfo: MethodType) if defn.isFunctionType(t) =>
-                t.derivedRefinedType(parent, rname, this(rinfo))
+              case t @ defn.RefinedFunctionOf(rinfo: MethodType) =>
+                t.derivedRefinedType(t.parent, t.refinedName, this(rinfo))
               case _ =>
                 mapOver(t)
             if variance > 0 then t1
@@ -845,7 +845,7 @@ class CheckCaptures extends Recheck, SymTransformer:
             case actual @ AppliedType(tycon, args) if defn.isNonRefinedFunction(actual) =>
               adaptFun(actual, args.init, args.last, expected, covariant, insertBox,
                   (aargs1, ares1) => actual.derivedAppliedType(tycon, aargs1 :+ ares1))
-            case actual @ RefinedType(_, _, rinfo: MethodType) if defn.isFunctionType(actual) =>
+            case actual @ defn.RefinedFunctionOf(rinfo: MethodType) =>
               // TODO Find a way to combine handling of generic and dependent function types (here and elsewhere)
               adaptFun(actual, rinfo.paramInfos, rinfo.resType, expected, covariant, insertBox,
                 (aargs1, ares1) =>
@@ -855,11 +855,11 @@ class CheckCaptures extends Recheck, SymTransformer:
               adaptFun(actual, actual.paramInfos, actual.resType, expected, covariant, insertBox,
                 (aargs1, ares1) =>
                   actual.derivedLambdaType(paramInfos = aargs1, resType = ares1))
-            case actual @ RefinedType(p, nme, rinfo: PolyType) if defn.isFunctionType(actual) =>
+            case actual @ defn.RefinedFunctionOf(rinfo: PolyType) =>
               adaptTypeFun(actual, rinfo.resType, expected, covariant, insertBox,
                 ares1 =>
                   val rinfo1 = rinfo.derivedLambdaType(rinfo.paramNames, rinfo.paramInfos, ares1)
-                  val actual1 = actual.derivedRefinedType(p, nme, rinfo1)
+                  val actual1 = actual.derivedRefinedType(actual.parent, actual.refinedName, rinfo1)
                   actual1
               )
             case _ =>
@@ -1080,7 +1080,7 @@ 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 defn.RefinedFunctionOf(rinfo: MethodType) =>
               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: MethodType) if defn.isFunctionType(tp1) =>
+      case tp1 @ defn.RefinedFunctionOf(rinfo: MethodType) =>
         val boxedRinfo = recur(rinfo)
         if boxedRinfo eq rinfo then tp
         else boxedRinfo.toFunctionType(alwaysDependent = true)
@@ -149,7 +149,7 @@ extends tpd.TreeTraverser:
                 tp.derivedAppliedType(tycon1, args1 :+ res1)
           else
             tp.derivedAppliedType(tycon1, args.mapConserve(arg => this(arg)))
-        case tp @ RefinedType(core, rname, rinfo: MethodType) if defn.isFunctionType(tp) =>
+        case defn.RefinedFunctionOf(rinfo: MethodType) =>
           val rinfo1 = apply(rinfo)
           if rinfo1 ne rinfo then rinfo1.toFunctionType(alwaysDependent = true)
           else tp

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

@@ -1129,6 +1129,20 @@ class Definitions {
     }
   }
 
+  object RefinedFunctionOf {
+    /** Matches a refined `PolyFunction`/`FunctionN[...]`/`ContextFunctionN[...]`.
+     *  Extracts the method type type and apply info.
+     */
+    def unapply(tpe: RefinedType)(using Context): Option[MethodOrPoly] = {
+      tpe.refinedInfo match
+        case mt: MethodOrPoly
+        if tpe.refinedName == nme.apply
+        && (tpe.parent.derivesFrom(defn.PolyFunctionClass) || isFunctionNType(tpe.parent)) =>
+          Some(mt)
+        case _ => None
+    }
+  }
+
   object PolyFunctionOf {
 
     /** Creates a refined `PolyFunction` with an `apply` method with the given info. */

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

@@ -4100,8 +4100,8 @@ object Types {
           tp.derivedAppliedType(tycon, addInto(args.head) :: Nil)
         case tp @ AppliedType(tycon, args) if defn.isFunctionNType(tp) =>
           wrapConvertible(tp.derivedAppliedType(tycon, args.init :+ addInto(args.last)))
-        case tp @ RefinedType(parent, rname, rinfo) if defn.isFunctionType(tp) =>
-          wrapConvertible(tp.derivedRefinedType(parent, rname, addInto(rinfo)))
+        case tp @ defn.RefinedFunctionOf(rinfo) =>
+          wrapConvertible(tp.derivedRefinedType(tp.parent, tp.refinedName, addInto(rinfo)))
         case tp: MethodOrPoly =>
           tp.derivedLambdaType(resType = addInto(tp.resType))
         case ExprType(resType) =>