Merge pull request #11858 from dotty-staging/fix-9276-alt

Only pickle StableRealizable flag for methods

Author: odersky

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

@@ -300,6 +300,11 @@ object Flags {
    *
    *  - the purity analysis used by the inliner to decide whether it is safe to elide, and
    *  - the TASTy reader of Scala 2.13, to determine whether there is a $init$ method.
+   *
+   *  StableRealizable is
+   *  - asserted for methods
+   *  - automatic in conjunction with Module or Enum vals
+   *  - cached for other vals
    */
   val (_, StableRealizable @ _, _) = newFlags(24, "<stable>")
 
@@ -584,6 +589,7 @@ object Flags {
   val MethodOrModule: FlagSet                = Method | Module
   val ParamForwarder: FlagSet                = Method | ParamAccessor | StableRealizable      // A parameter forwarder
   val PrivateMethod: FlagSet                 = Method | Private
+  val StableMethod: FlagSet                  = Method | StableRealizable
   val NoInitsInterface: FlagSet              = NoInits | PureInterface
   val NoInitsTrait: FlagSet                  = NoInits | Trait                                // A trait that does not need to be initialized
   val ValidForeverFlags: FlagSet             = Package | Permanent | Scala2SpecialFlags

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -740,7 +740,7 @@ class TreePickler(pickler: TastyPickler) {
       if (flags.is(Accessor)) writeModTag(FIELDaccessor)
       if (flags.is(CaseAccessor)) writeModTag(CASEaccessor)
       if (flags.is(HasDefault)) writeModTag(HASDEFAULT)
-      if (flags.is(StableRealizable)) writeModTag(STABLE)
+      if flags.isAllOf(StableMethod) then writeModTag(STABLE) // other StableRealizable flag occurrences are either implied or can be recomputed
       if (flags.is(Extension)) writeModTag(EXTENSION)
       if (flags.is(ParamAccessor)) writeModTag(PARAMsetter)
       if (flags.is(SuperParamAlias)) writeModTag(PARAMalias)

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -487,7 +487,9 @@ class TreeUnpickler(reader: TastyReader,
       if (lacksDefinition && tag != PARAM) flags |= Deferred
       if (tag == DEFDEF) flags |= Method
       if (givenFlags.is(Module))
-        flags = flags | (if (tag == VALDEF) ModuleValCreationFlags else ModuleClassCreationFlags)
+        flags |= (if (tag == VALDEF) ModuleValCreationFlags else ModuleClassCreationFlags)
+      if flags.is(Enum, butNot = Method) && name.isTermName then
+        flags |= StableRealizable
       if (ctx.owner.isClass) {
         if (tag == TYPEPARAM) flags |= Param
         else if (tag == PARAM) {