Harden resultTypeApprox

Author: odersky

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

@@ -142,9 +142,12 @@ object Types {
     /** Is this type a value type? */
     final def isValueType: Boolean = this.isInstanceOf[ValueType]
 
-    /** Is the is value type or type lambda? */
+    /** Is this a value type or a type lambda? */
     final def isValueTypeOrLambda: Boolean = isValueType || this.isInstanceOf[TypeLambda]
 
+    /** Is this a value type or a wildcard? */
+    final def isValueTypeOrWildcard: Boolean = isValueType || this.isInstanceOf[WildcardType]
+
     /** Does this type denote a stable reference (i.e. singleton type)? */
     final def isStable(implicit ctx: Context): Boolean = stripTypeVar match {
       case tp: TermRef => tp.termSymbol.isStable && tp.prefix.isStable || tp.info.isStable
@@ -1524,11 +1527,8 @@ object Types {
   /** A marker trait for types that can be types of values or prototypes of value types */
   trait ValueTypeOrProto extends TermType
 
-  /** A marker trait for types that can be types of values or wildcards */
-  trait ValueTypeOrWildcard extends TermType
-
   /** A marker trait for types that can be types of values or that are higher-kinded  */
-  trait ValueType extends ValueTypeOrProto with ValueTypeOrWildcard
+  trait ValueType extends ValueTypeOrProto
 
   /** A marker trait for types that are guaranteed to contain only a
    *  single non-null value (they might contain null in addition).
@@ -2480,8 +2480,8 @@ object Types {
 
   object AndType {
     def apply(tp1: Type, tp2: Type)(implicit ctx: Context): AndType = {
-      assert(tp1.isInstanceOf[ValueTypeOrWildcard] &&
-             tp2.isInstanceOf[ValueTypeOrWildcard], i"$tp1 & $tp2 / " + s"$tp1 & $tp2")
+      assert(tp1.isValueTypeOrWildcard &&
+             tp2.isValueTypeOrWildcard, i"$tp1 & $tp2 / " + s"$tp1 & $tp2")
       unchecked(tp1, tp2)
     }
 
@@ -2525,8 +2525,8 @@ object Types {
       myBaseClasses
     }
 
-    assert(tp1.isInstanceOf[ValueTypeOrWildcard] &&
-           tp2.isInstanceOf[ValueTypeOrWildcard], s"$tp1 $tp2")
+    assert(tp1.isValueTypeOrWildcard &&
+           tp2.isValueTypeOrWildcard, s"$tp1 $tp2")
 
     private[this] var myJoin: Type = _
     private[this] var myJoinPeriod: Period = Nowhere
@@ -3757,7 +3757,7 @@ object Types {
   object TryDynamicCallType extends FlexType
 
   /** Wildcard type, possibly with bounds */
-  abstract case class WildcardType(optBounds: Type) extends CachedGroundType with ValueTypeOrWildcard {
+  abstract case class WildcardType(optBounds: Type) extends CachedGroundType with TermType {
     def derivedWildcardType(optBounds: Type)(implicit ctx: Context) =
       if (optBounds eq this.optBounds) this
       else if (!optBounds.exists) WildcardType

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

@@ -472,16 +472,18 @@ object ProtoTypes {
   }
 
   /** Create a new TypeVar that represents a dependent method parameter singleton */
-  def newDepTypeVar(tp: Type)(implicit ctx: Context): TypeVar =
+  def newDepTypeVar(tp: Type)(implicit ctx: Context): TypeVar = {
     newTypeVar(TypeBounds.upper(AndType(tp.widenExpr, defn.SingletonClass.typeRef)))
-
+  }
   /** The result type of `mt`, where all references to parameters of `mt` are
    *  replaced by either wildcards (if typevarsMissContext) or TypeParamRefs.
    */
   def resultTypeApprox(mt: MethodType)(implicit ctx: Context): Type =
     if (mt.isResultDependent) {
       def replacement(tp: Type) =
-        if (ctx.mode.is(Mode.TypevarsMissContext)) WildcardType else newDepTypeVar(tp)
+        if (ctx.mode.is(Mode.TypevarsMissContext) ||
+            !tp.widenExpr.isValueTypeOrWildcard) WildcardType
+        else newDepTypeVar(tp)
       mt.resultType.substParams(mt, mt.paramInfos.map(replacement))
     }
     else mt.resultType

tests/neg/parser-stability-17.scala

@@ -1,2 +1,2 @@
-trait x0[] {      x0: x0 => }
-        class x0[x1] extends x0[x0 x0] x2 x0
+trait x0[] {      x0: x0 => }      // error // error
+        class x0[x1] extends x0[x0 x0] x2 x0  // error // error

tests/neg/parser-stability-19.scala

@@ -0,0 +1,4 @@
+object x0 {
+  case class x0[]                     // error // error
+    def x0( ) ]                       // error // error
+    def x0 ( x0:x0 ):x0.type = x1 x0  // error // error // error