address review

Author: liufengyun

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

@@ -67,17 +67,17 @@ object Checkable {
     def isAbstract(P: Type) = !P.dealias.typeSymbol.isClass
     def isPatternTypeSymbol(sym: Symbol) = !sym.isClass && sym.is(Case)
 
-    def replaceP(implicit ctx: Context) = new TypeMap {
+    def replaceP(tp: Type)(implicit ctx: Context) = new TypeMap {
       def apply(tp: Type) = tp match {
         case tref: TypeRef
         if isPatternTypeSymbol(tref.typeSymbol) => WildcardType
         case AnnotatedType(_, annot)
         if annot.symbol == defn.UncheckedAnnot => WildcardType
         case _ => mapOver(tp)
       }
-    }
+    }.apply(tp)
 
-    def replaceX(implicit ctx: Context) = new TypeMap {
+    def replaceX(tp: Type)(implicit ctx: Context) = new TypeMap {
       def apply(tp: Type) = tp match {
         case tref: TypeRef
         if isPatternTypeSymbol(tref.typeSymbol) =>
@@ -86,18 +86,19 @@ object Checkable {
           else OrType(defn.AnyType, defn.NothingType)
         case _ => mapOver(tp)
       }
-    }
+    }.apply(tp)
 
-    def stripTypeParam(implicit ctx: Context) = new ApproximatingTypeMap {
+    /** Approximate type parameters depending on variance */
+    def stripTypeParam(tp: Type)(implicit ctx: Context) = new ApproximatingTypeMap {
       def apply(tp: Type): Type = tp match {
         case tp: TypeRef if tp.underlying.isInstanceOf[TypeBounds] =>
-          val lo = this(tp.info.loBound)
-          val hi = this(tp.info.hiBound)
+          val lo = apply(tp.info.loBound)
+          val hi = apply(tp.info.hiBound)
           range(lo, hi)
         case _ =>
           mapOver(tp)
       }
-    }
+    }.apply(tp)
 
     def isClassDetermined(X: Type, P: AppliedType)(implicit ctx: Context) = {
       val AppliedType(tycon, _) = P
@@ -131,16 +132,17 @@ object Checkable {
           case _                   => recur(defn.AnyType, tpT)
         }
       case tpe: AppliedType     =>
+        // first try withou striping type parameters for performance
         isClassDetermined(X, tpe)(ctx.fresh.setNewTyperState()) ||
-        isClassDetermined(stripTypeParam.apply(X), tpe)(ctx.fresh.setNewTyperState())
+        isClassDetermined(stripTypeParam(X), tpe)(ctx.fresh.setNewTyperState())
       case AndType(tp1, tp2)    => recur(X, tp1) && recur(X, tp2)
       case OrType(tp1, tp2)     => recur(X, tp1) && recur(X, tp2)
       case AnnotatedType(t, _)  => recur(X, t)
       case _: RefinedType       => false
       case _                    => true
     })
 
-    val res = recur(replaceX.apply(X.widen), replaceP.apply(P))
+    val res = recur(replaceX(X.widen), replaceP(P))
 
     debug.println(i"checking  ${X.show} isInstanceOf ${P} = $res")