ElimRepeated: Do not use installAfter

This was a mistake introduced in the previous commit, installAfter is
only safe to use in `IdentityDenotTransformer` phases, otherwise it
means that the phase denotation transformer is not run at all for this
particular denotation, this caused Ycheck to fail.

Author: smarter

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

@@ -32,8 +32,21 @@ class ElimRepeated extends MiniPhaseTransform with InfoTransformer with Annotati
   def transformInfo(tp: Type, sym: Symbol)(implicit ctx: Context): Type =
     elimRepeated(tp)
 
+
+  override def transform(ref: SingleDenotation)(implicit ctx: Context): SingleDenotation =
+    super.transform(ref) match {
+      case ref1: SymDenotation if (ref1 ne ref) && overridesJava(ref1.symbol) =>
+        // This method won't override the corresponding Java method at the end of this phase,
+        // only the bridge added by `addVarArgsBridge` will.
+        ref1.copySymDenotation(initFlags = ref1.flags &~ Override)
+      case ref1 =>
+        ref1
+    }
+
   override def mayChange(sym: Symbol)(implicit ctx: Context): Boolean = sym is Method
 
+  private def overridesJava(sym: Symbol)(implicit ctx: Context) = sym.allOverriddenSymbols.exists(_ is JavaDefined)
+
   private def elimRepeated(tp: Type)(implicit ctx: Context): Type = tp.stripTypeVar match {
     case tp @ MethodType(paramNames, paramTypes) =>
       val resultType1 = elimRepeated(tp.resultType)
@@ -93,8 +106,7 @@ class ElimRepeated extends MiniPhaseTransform with InfoTransformer with Annotati
    */
   override def transformDefDef(tree: DefDef)(implicit ctx: Context, info: TransformerInfo): Tree = {
     assert(ctx.phase == thisTransformer)
-    def overridesJava = tree.symbol.allOverriddenSymbols.exists(_ is JavaDefined)
-    if (tree.symbol.info.isVarArgsMethod && overridesJava)
+    if (tree.symbol.info.isVarArgsMethod && overridesJava(tree.symbol))
       addVarArgsBridge(tree)
     else
       tree
@@ -121,10 +133,6 @@ class ElimRepeated extends MiniPhaseTransform with InfoTransformer with Annotati
         .appliedToArgss(vrefss1)
     })
 
-    // Drop the override flag on the user-written method, only the added bridge
-    // is a real override.
-    original.copySymDenotation(initFlags = original.flags &~ Override).installAfter(thisTransformer)
-
     Thicket(ddef, bridgeDef)
   }