Drop isAbstractType

Always use isAbstractorParamType. quotes.reflect still uses isAbstractType for backwards compatibility,
but it now also includes type parameters. This was the case anyway before for type parameters set up by
Namer.

[Cherry-picked aaacc43]

Author: odersky

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

@@ -684,9 +684,6 @@ object SymDenotations {
     def isWrappedToplevelDef(using Context): Boolean =
       !isConstructor && owner.isPackageObject
 
-    /** Is this symbol an abstract type? */
-    final def isAbstractType(using Context): Boolean = this.is(DeferredType)
-
     /** Is this symbol an alias type? */
     final def isAliasType(using Context): Boolean =
       isAbstractOrAliasType && !isAbstractOrParamType

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

@@ -2571,7 +2571,7 @@ object Types extends TypeUtils {
       symd.maybeOwner.membersNeedAsSeenFrom(prefix) && !symd.is(NonMember)
       || prefix.match
         case prefix: Types.ThisType =>
-          (symd.isAbstractType
+          (symd.isAbstractOrParamType
             || symd.isTerm
                 && !symd.flagsUNSAFE.isOneOf(Module | Final | Param)
                 && !symd.isConstructor

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -2649,7 +2649,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def isAliasType: Boolean = self.denot.isAliasType
         def isAnonymousClass: Boolean = self.denot.isAnonymousClass
         def isAnonymousFunction: Boolean = self.denot.isAnonymousFunction
-        def isAbstractType: Boolean = self.denot.isAbstractType
+        def isAbstractType: Boolean = self.denot.isAbstractOrParamType
         def isClassConstructor: Boolean = self.denot.isClassConstructor
         def isType: Boolean = self.isType
         def isTerm: Boolean = self.isTerm

library/src/scala/quoted/Quotes.scala

@@ -3993,7 +3993,7 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
         /** Is this symbol an anonymous function? */
         def isAnonymousFunction: Boolean
 
-        /** Is this symbol an abstract type? */
+        /** Is this symbol an abstract type or a type parameter? */
         def isAbstractType: Boolean
 
         /** Is this the constructor of a class? */