Use isProvisional helper method

... to avoid proliferation of flagsUNSAFE

Author: odersky

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

@@ -658,6 +658,9 @@ object SymDenotations {
       containsOpaques ||
       is(Module, butNot = Package) && owner.seesOpaques
 
+    def isProvisional(using Context): Boolean =
+      flagsUNSAFE.is(Provisional) // do not force the info to check the flag
+
     /** Is this the denotation of a self symbol of some class?
      *  This is the case if one of two conditions holds:
      *  1. It is the symbol referred to in the selfInfo part of the ClassInfo

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

@@ -285,7 +285,7 @@ class TypeApplications(val self: Type) extends AnyVal {
   /** Dealias type if it can be done without forcing the TypeRef's info */
   def safeDealias(using Context): Type = self match {
     case self: TypeRef
-    if self.denot.exists && self.symbol.isAliasType && !self.symbol.flagsUNSAFE.is(Provisional) =>
+    if self.denot.exists && self.symbol.isAliasType && !self.symbol.isProvisional =>
       self.superType.stripTypeVar.safeDealias
     case _ =>
       self

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

@@ -118,7 +118,7 @@ object Types {
             case t: TypeRef =>
               !t.currentSymbol.isStatic && {
                 (t: Type).mightBeProvisional = false // break cycles
-                t.symbol.flagsUNSAFE.is(Provisional)
+                t.symbol.isProvisional
                 || test(t.prefix, theAcc)
                 || t.denot.infoOrCompleter.match
                     case info: LazyType => true

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

@@ -2030,7 +2030,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       if tycon == defn.andType || tycon == defn.orType then
         checkedArgs = checkedArgs.mapconserve(arg =>
           checkSimpleKinded(checkNoWildcard(arg)))
-      else if tycon.flagsUNSAFE.is(Provisional) then
+      else if tycon.isProvisional then
         // A type with Provisional flag is either an alias or abstract type.
         // If it is an alias type, it would mean the type is cyclic
         // If it is an abstract type, it would mean the type is an irreducible