Create the symbol at the next phase

Create the symbol at the next phase, so that it is a valid member of the
corresponding function for all valid periods of its SymDenotations.
Otherwise, the valid period will offset by 1, which causes a stale symbol
in compiling stdlib.

Author: liufengyun

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

@@ -2,7 +2,7 @@ package dotty.tools.dotc
 package transform
 
 import ast.Trees._, ast.tpd, core._
-import Contexts.Context, Types._, Decorators._, Symbols._, DenotTransformers._
+import Contexts._, Types._, Decorators._, Symbols._, DenotTransformers._
 import SymDenotations._, Scopes._, StdNames._, NameOps._, Names._
 import MegaPhase.MiniPhase
 
@@ -24,7 +24,11 @@ class SpecializedApplyMethods extends MiniPhase with InfoTransformer {
 
   private def specApplySymbol(sym: Symbol, args: List[Type], ret: Type)(using Context): Symbol = {
     val name = nme.apply.specializedFunction(ret, args)
-    newSymbol(sym, name, Flags.Method, MethodType(args, ret))
+    // Create the symbol at the next phase, so that it is a valid member of the
+    // corresponding function for all valid periods of its SymDenotations.
+    // Otherwise, the valid period will offset by 1, which causes a stale symbol
+    // in compiling stdlib.
+    atNextPhase(newSymbol(sym, name, Flags.Method, MethodType(args, ret)))
   }
 
   private def specFun0(op: Type => Unit)(using Context): Unit = {
@@ -84,7 +88,7 @@ class SpecializedApplyMethods extends MiniPhase with InfoTransformer {
     def synthesizeApply(names: collection.Set[TermName]): Tree = {
       val applyBuf = new mutable.ListBuffer[DefDef]
       names.foreach { name =>
-        val applySym = cls.info.decls.lookup(name)
+        val applySym = atNextPhase(cls.info.decls.lookup(name))
         val ddef = DefDef(
           applySym.asTerm,
           { vparamss =>