Make constructors effectively final

This is mainly a cleanup.

Author: odersky

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

@@ -1196,6 +1196,7 @@ object SymDenotations {
       isOneOf(EffectivelyFinalFlags)
       || is(Inline, butNot = Deferred)
       || is(JavaDefinedVal, butNot = Method)
+      || isConstructor
       || !owner.isExtensibleClass
 
     /** A class is effectively sealed if has the `final` or `sealed` modifier, or it

compiler/src/dotty/tools/dotc/transform/init/Util.scala

@@ -75,11 +75,9 @@ object Util:
       case _ =>
         None
 
-  def resolve(cls: ClassSymbol, sym: Symbol)(using Context): Symbol = log("resove " + cls + ", " + sym, printer, (_: Symbol).show) {
-    if (sym.isEffectivelyFinal || sym.isConstructor) sym
+  def resolve(cls: ClassSymbol, sym: Symbol)(using Context): Symbol = log("resove " + cls + ", " + sym, printer, (_: Symbol).show):
+    if sym.isEffectivelyFinal then sym
     else sym.matchingMember(cls.appliedRef)
-  }
-
 
   extension (sym: Symbol)
     def hasSource(using Context): Boolean = !sym.defTree.isEmpty

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

@@ -1689,7 +1689,7 @@ class RefChecks extends MiniPhase { thisPhase =>
             // if (settings.warnNullaryUnit)
             //  checkNullaryMethodReturnType(sym)
             // if (settings.warnInaccessible) {
-            //  if (!sym.isConstructor && !sym.isEffectivelyFinal && !sym.isSynthetic)
+            //  if (!sym.isEffectivelyFinal && !sym.isSynthetic)
             //    checkAccessibilityOfReferencedTypes(tree)
             // }
             // tree match {