Reduce flag fiddling

There isn't much point to the late* flags in a world where
we're mutating flags left and right in tree and info transformers...

So, lets get rid of the indirection until we can include flags
in a symbol's type history, like we do for its info.

This retires lateDEFERRED (redundant with SYNTHESIZE_IMPL_IN_SUBCLASS).
Since it's introduced so late, it makes little sense to have these
synthetic members go back to DEFERRED. Instead, just set DEFERRED directly.

Also remove unused late* and not* flags.
notPRIVATE subsumes lateFINAL for effective finality (scala/scala-dev#126)

2 files changed, 26 insertions, 38 deletions

diff --git a/src/reflect/scala/reflect/internal/Flags.scala b/src/reflect/scala/reflect/internal/Flags.scala
index d088150db6..a146f9aea5 100644
--- a/src/reflect/scala/reflect/internal/Flags.scala
+++ b/src/reflect/scala/reflect/internal/Flags.scala
@@ -178,13 +178,14 @@ class Flags extends ModifierFlags {
   //
   // Flags from 1L to (1L << 50) are normal flags.
   //
-  // The flags DEFERRED (1L << 4) to MODULE (1L << 8) have a `late` counterpart. Late flags change
-  // their counterpart from 0 to 1 after a specific phase (see below). The first late flag
-  // (lateDEFERRED) is at (1L << 51), i.e., late flags are shifted by 47. The last one is (1L << 55).
+  // The "late" counterpart to flags DEFERRED (1L << 4) to MODULE (1L << 8)
+  // show up in `sym.flags` as their regular counterpart once the phase mask admits them (see below).
+  // The first late flag (lateDEFERRED) is at (1L << 51), i.e., late flags are shifted by 47. The last one is (1L << 55).
+  // Think of it as a poor man's flag history akin to the type history for a symbol's info.
   //
-  // The flags PROTECTED (1L) to PRIVATE (1L << 2) have a `not` counterpart. Negated flags change
-  // their counterpart from 1 to 0 after a specific phase (see below). They are shifted by 56, i.e.,
-  // the first negated flag (notPROTECTED) is at (1L << 56), the last at (1L << 58).
+  // The "not" counterpart to flags PROTECTED (1L) to PRIVATE (1L << 2)
+  // are negated flags that suppress their counterpart after a specific phase (see below).
+  // They are shifted by 56, i.e., the first negated flag (notPROTECTED) is at (1L << 56), the last at (1L << 58).
   //
   // Late and negative flags are only enabled after certain phases, implemented by the phaseNewFlags
   // method of the SubComponent, so they implement a bit of a flag history.
@@ -216,20 +217,15 @@ class Flags extends ModifierFlags {
   //       erasure  15  [START] <latedeferred>
   //         mixin  20  [START] <latemodule> <notoverride>
   //
-  // lateMETHOD set in RefChecks#transformInfo.
-  // lateFINAL set in Symbols#makeNotPrivate.
   // notPRIVATE set in Symbols#makeNotPrivate, IExplicitOuter#transform, Inliners.
   // notPROTECTED set in ExplicitOuter#transform.
-  // lateDEFERRED set in AddInterfaces, Mixin, etc.
-  // lateMODULE set in Mixin#transformInfo.
-  // notOVERRIDE set in Mixin#preTransform.
 
-  final val lateDEFERRED  = (DEFERRED: Long) << LateShift
-  final val lateFINAL     = (FINAL: Long) << LateShift
-  final val lateMETHOD    = (METHOD: Long) << LateShift
-  final val lateMODULE    = (MODULE: Long) << LateShift
+//  final val lateDEFERRED  = (DEFERRED: Long) << LateShift // unused
+//  final val lateFINAL     = (FINAL: Long) << LateShift    // only used for inliner -- could be subsumed by notPRIVATE?
+//  final val lateMETHOD    = (METHOD: Long) << LateShift   // unused
+//  final val lateMODULE    = (MODULE: Long) << LateShift   // unused
 
-  final val notOVERRIDE   = (OVERRIDE: Long) << AntiShift
+//  final val notOVERRIDE   = (OVERRIDE: Long) << AntiShift // unused
   final val notPRIVATE    = (PRIVATE: Long) << AntiShift
   final val notPROTECTED  = (PROTECTED: Long) << AntiShift
 
@@ -449,13 +445,13 @@ class Flags extends ModifierFlags {
     case           JAVA_ENUM => "<enum>"                              // (1L << 48)
     case     JAVA_ANNOTATION => "<annotation>"                        // (1L << 49)
     case SYNTHESIZE_IMPL_IN_SUBCLASS => "<sub_synth>"                 // (1L << 50)
-    case      `lateDEFERRED` => "<latedeferred>"                      // (1L << 51)
-    case         `lateFINAL` => "<latefinal>"                         // (1L << 52)
-    case        `lateMETHOD` => "<latemethod>"                        // (1L << 53)
-    case   0x80000000000000L => ""                                    // (1L << 54)
-    case        `lateMODULE` => "<latemodule>"                        // (1L << 55)
+    case   0x08000000000000L => "<latedeferred>"                      // (1L << 51)
+    case   0x10000000000000L => "<latefinal>"                         // (1L << 52)
+    case   0x20000000000000L => "<latemethod>"                        // (1L << 53)
+    case   0x40000000000000L => ""                                    // (1L << 54)
+    case   0x80000000000000L => "<latemodule>"                        // (1L << 55)
     case      `notPROTECTED` => "<notprotected>"                      // (1L << 56)
-    case       `notOVERRIDE` => "<notoverride>"                       // (1L << 57)
+    case  0x200000000000000L => "<notoverride>"                       // (1L << 57)
     case        `notPRIVATE` => "<notprivate>"                        // (1L << 58)
     case NEEDS_TREES         => "<needs_trees>"                       // (1L << 59)
     case 0x1000000000000000L => ""                                    // (1L << 60)
diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index e438856160..487aadf5e5 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -746,10 +746,10 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     final def hasGetter = isTerm && nme.isLocalName(name)
 
     /**
-     * Nested modules which have no static owner when ModuleDefs are eliminated (refchecks) are
-     * given the lateMETHOD flag, which makes them appear as methods after refchecks.
+     * Nested modules with a non-static owner receive the METHOD flag during UnCurry's info transform.
+     * (They are replaced by a ClassDef and DefDef for the module accessor during the fields phase.)
      *
-     * Note: the lateMETHOD flag is added lazily in the info transformer of the RefChecks phase.
+     * Note: the METHOD flag is added lazily in the info transformer of the UnCurry phase.
      * This means that forcing the `sym.info` may change the value of `sym.isMethod`. Forcing the
      * info is in the responsibility of the caller. Doing it eagerly here was tried (0ccdb151f) but
      * has proven to lead to bugs (SI-8907).
@@ -985,10 +985,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     final def isEffectivelyFinal: Boolean = (
          (this hasFlag FINAL | PACKAGE)
       || isModuleOrModuleClass && (isTopLevel || !settings.overrideObjects)
-      || isTerm && (
-             isPrivate
-          || isLocalToBlock
-         )
+      || isTerm && (isPrivate || isLocalToBlock || (hasAllFlags(notPRIVATE | METHOD) && !hasFlag(DEFERRED)))
       || isClass && originalOwner.isTerm && children.isEmpty // we track known subclasses of term-owned classes, use that infer finality
     )
     /** Is this symbol effectively final or a concrete term member of sealed class whose children do not override it */
@@ -2450,14 +2447,9 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
      */
     final def makeNotPrivate(base: Symbol) {
       if (this.isPrivate) {
-        setFlag(notPRIVATE)
-        // Marking these methods final causes problems for proxies which use subclassing. If people
-        // write their code with no usage of final, we probably shouldn't introduce it ourselves
-        // unless we know it is safe. ... Unfortunately if they aren't marked final the inliner
-        // thinks it can't inline them. So once again marking lateFINAL, and in genjvm we no longer
-        // generate ACC_FINAL on "final" methods which are actually lateFINAL.
-        if (isMethod && !isDeferred)
-          setFlag(lateFINAL)
+        setFlag(notPRIVATE) // this makes it effectively final (isEffectivelyFinal)
+        // don't set FINAL -- methods not marked final by user should not end up final in bytecode
+        // inliner will know it's effectively final (notPRIVATE non-deferred method)
         if (!isStaticModule && !isClassConstructor) {
           expandName(base)
           if (isModule) moduleClass.makeNotPrivate(base)
@@ -2886,7 +2878,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
 
     override def owner = {
       if (Statistics.hotEnabled) Statistics.incCounter(ownerCount)
-      // a module symbol may have the lateMETHOD flag after refchecks, see isModuleNotMethod
+      // a non-static module symbol gets the METHOD flag in uncurry's info transform -- see isModuleNotMethod
       if (!isMethod && needsFlatClasses) rawowner.owner
       else rawowner
     }