Run RefChecks at group end

Move to end of group. Needed a fix in ExtensionMethods to work
correctly. Before the fix, extension methods got wrong flags.

Author: odersky

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -53,15 +53,15 @@ class Compiler {
            new ElimJavaPackages),   // Eliminate syntactic references to Java packages
       List(new CheckStatic,         // Check restrictions that apply to @static members
            new ElimRepeated,        // Rewrite vararg parameters and arguments
-           new RefChecks,           // Various checks mostly related to abstract members and overriding
            new NormalizeFlags,      // Rewrite some definition flags
            new ExtensionMethods,    // Expand methods of value classes with extension methods
            new ExpandSAMs,          // Expand single abstract method closures to anonymous classes
            new TailRec,             // Rewrite tail recursion to loops
            new ByNameClosures,      // Expand arguments to by-name parameters to closures
            new LiftTry,             // Put try expressions that might execute on non-empty stacks into their own methods
            new HoistSuperArgs,      // Hoist complex arguments of supercalls to enclosing scope
-           new ClassOf),            // Expand `Predef.classOf` calls.
+           new ClassOf,            // Expand `Predef.classOf` calls.
+           new RefChecks),           // Various checks mostly related to abstract members and overriding
       List(new TryCatchPatterns,    // Compile cases in try/catch
            new PatternMatcher,      // Compile pattern matches
            new ExplicitOuter,       // Add accessors to outer classes from nested ones.

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

@@ -21,6 +21,9 @@ class ClassOf extends MiniPhaseTransform {
 
   override def phaseName: String = "classOf"
 
+  override def treeTransformPhase(implicit ctx: Context, info: TransformerInfo) =
+    groupEndPhase
+
   override def transformTypeApply(tree: TypeApply)(implicit ctx: Context, info: TransformerInfo): Tree =
     if (tree.symbol eq defn.Predef_classOf) {
       val targ = tree.args.head.tpe

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

@@ -134,7 +134,7 @@ class ExtensionMethods extends MiniPhaseTransform with DenotTransformer with Ful
   private def createExtensionMethod(imeth: Symbol, staticClass: Symbol)(implicit ctx: Context): TermSymbol = {
     val extensionName = extensionNames(imeth).head.toTermName
     val extensionMeth = ctx.newSymbol(staticClass, extensionName,
-      imeth.flags | Final &~ (Override | Protected | AbsOverride),
+      (imeth.flags | Final) &~ (Override | Protected | AbsOverride),
       fullyParameterizedType(imeth.info, imeth.owner.asClass),
       privateWithin = imeth.privateWithin, coord = imeth.coord)
     extensionMeth.addAnnotations(imeth.annotations)(ctx.withPhase(thisTransformer))

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

@@ -806,9 +806,8 @@ class RefChecks extends MiniPhase { thisTransformer =>
   class Transform(currentLevel: RefChecks.OptLevelInfo = RefChecks.NoLevelInfo) extends TreeTransform {
     def phase = thisTransformer
 
-    // Errors when run at end of group
-    //override def treeTransformPhase(implicit ctx: Context, info: TransformerInfo) =
-    //  groupEndPhase
+    override def treeTransformPhase(implicit ctx: Context, info: TransformerInfo) =
+      groupEndPhase
 
     override def prepareForStats(trees: List[Tree])(implicit ctx: Context) = {
       // println(i"preparing for $trees%; %, owner = ${ctx.owner}")