fields phase

the info-transformed of constructors:
  - traits receive trait-setters for vals
  - classes receive fields & accessors for mixed in traits

Constructors tree transformer
  - makes trees for decls added during above info transform
  - adds mixin super calls to the primary constructor

```
trait OneConcreteVal[T] {
var x = 1 // : T = ???
def foo = x
}

trait OneOtherConcreteVal[T] {
var y: T = ???
}

class C extends OneConcreteVal[Int] with OneOtherConcreteVal[String]
```

we don't have a field -- only a getter -- so,
where will we keep non-getter but-field annotations?

mixin only deals with lazy accessors/vals

do not used referenced to correlate getter/setter
it messes with paramaccessor's usage, and we don't really need it

make sure to clone info's, so we don't share symbols for method args
this manifests itself as an exception in lambdalift, finding proxies

Use NEEDS_TREES for all comms between InfoTransform and tree transform

yep, need SYNTHESIZE_IMPL_IN_SUBCLASS

distinguish accessors that should be mixed into subclass,
and those that simply need to be implemented in tree transform,
after info transform added the decl

commit 4b4932e
Author: Adriaan Moors <[email protected]>
Date:   6 days ago

    do assignment to trait fields in AddInterfaces

    regular class vals get assignments during constructors, as before

impl classes get accessors + assignments through trait setters in addinterfaces
so that constructors acts on them there,
and produced the init method in the required spot (the impl class)

bootstrapped compiler needs new partest

commit baf568d
Author: Adriaan Moors <[email protected]>
Date:   3 weeks ago

    produce identical bytecode for constant trait val getters

    I couldn't bring myself to emit the unused fields that we
    used to emit for constant vals, even though the getters
    immediately return the constant, and thus the field goes unused.

    In the next version, there's no need to synthesize impls
    for these in subclasses -- the getter can be implemented
    in the interface.

commit b9052da
Author: Lukas Rytz <[email protected]>
Date:   3 weeks ago

    Fix enclosing method attribute for classes nested in trait fields

    Trait fields are now created as MethodSymbol (no longer TermSymbol).
    This symbol shows up in the `originalOwner` chain of a class declared
    within the field initializer. This promoted the field getter to
    being the enclosing method of the nested class, which it is not
    (the EnclosingMethod attribute is a source-level property).

commit cf845ab
Author: Adriaan Moors <[email protected]>
Date:   3 weeks ago

    don't suppress field for unit-typed vals

    it affects the memory model -- even a write of unit to a field is relevant...

commit 337a9dd
Author: Adriaan Moors <[email protected]>
Date:   4 weeks ago

    unit-typed lazy vals should never receive a field

    this need was unmasked by test/files/run/t7843-jsr223-service.scala,
    which no longer printed the output expected from the `0 to 10 foreach`

    Currently failing tests:

     - test/files/pos/t6780.scala
     - test/files/neg/anytrait.scala
     - test/files/neg/delayed-init-ref.scala
     - test/files/neg/t562.scala
     - test/files/neg/t6276.scala
     - test/files/run/delambdafy_uncurry_byname_inline.scala
     - test/files/run/delambdafy_uncurry_byname_method.scala
     - test/files/run/delambdafy_uncurry_inline.scala
     - test/files/run/delambdafy_uncurry_method.scala
     - test/files/run/inner-obj-auto.scala
     - test/files/run/lazy-traits.scala
     - test/files/run/reify_lazyunit.scala
     - test/files/run/showraw_mods.scala
     - test/files/run/t3670.scala
     - test/files/run/t3980.scala
     - test/files/run/t4047.scala
     - test/files/run/t6622.scala
     - test/files/run/t7406.scala
     - test/files/run/t7843-jsr223-service.scala
     - test/files/jvm/innerClassAttribute
     - test/files/specialized/SI-7343.scala
     - test/files/specialized/constant_lambda.scala
     - test/files/specialized/spec-early.scala
     - test/files/specialized/spec-init.scala
     - test/files/specialized/spec-matrix-new.scala
     - test/files/specialized/spec-matrix-old.scala
     - test/files/presentation/scope-completion-3

commit b1b4e5c
Author: Adriaan Moors <[email protected]>
Date:   4 weeks ago

    wip: lambdalift fix

    test/files/trait-defaults/lambdalift.scala works,
    but still some related tests failing

    (note that we can't use a bootstrapped compiler yet
    due to binary incompatibility in partest)

commit eae7dac
Author: Adriaan Moors <[email protected]>
Date:   4 weeks ago

    update check now that trait vals can be concrete, use names not letters

    note the progression in a concrete trait val now being recognized as such
    ```
    -trait T => true
    -method $init$ => false
    -value z1 => true
    -value z2 => true // z2 is actually concrete!
    ```

commit 6555c74
Author: Adriaan Moors <[email protected]>
Date:   4 weeks ago

    bootstraps again by running info transform once per class...

    not sure how this ever worked, as separate compilation would transform a trait's info
    multiple times, resulting in double defs...

commit 273cb20
Author: Adriaan Moors <[email protected]>
Date:   6 weeks ago

    skip presuper vals in new encoding

commit 728e71e
Author: Adriaan Moors <[email protected]>
Date:   6 weeks ago

    incoherent cyclic references between synthesized members

    must replace old trait accessor symbols by mixed in symbols
    in the infos of the mixed in symbols

    ```
    trait T { val a: String ; val b: a.type }
    class C extends T {
      // a, b synthesized, but the a in b's type, a.type, refers to the original symbol, not the clone in C
    }
    ```

    symbols occurring in types of synthesized members
    do not get rebound to other synthesized symbols

    package <empty>#4 {
      abstract <defaultparam/trait> trait N#7352 extends scala#22.AnyRef#2378 {
        <method> <deferred> <mutable> <accessor> <triedcooking> <sub_synth> def N$_setter_$self_$eq#15011(x$1#15012: <empty>#3.this.N#7352): scala#23.this.Unit#2340;
        <method> <deferred> <mutable> <accessor> <triedcooking> <sub_synth> def N$_setter_$n_$eq#15013(x$1#15014: N#7352.this.self#7442.type): scala#23.this.Unit#2340;
        <method> def /*N*/$init$scala#7441(): scala#23.this.Unit#2340 = {
          ()
        };
        <method> <deferred> <stable> <accessor> <triedcooking> <sub_synth> def self#7442: <empty>#3.this.N#7352;
        N#7352.this.N$_setter_$self_$eq#15011(scala#22.Predef#1729.$qmark$qmark$qmark#6917);
        <method> <deferred> <stable> <accessor> <sub_synth> def n#7443: N#7352.this.self#7442.type;
        N#7352.this.N$_setter_$n_$eq#15013(N#7352.this.self#7442)
      };
      abstract class M#7353 extends scala#22.AnyRef#2378 {
        <method> <triedcooking> def <init>#13465(): <empty>#3.this.M#7353 = {
          M#7353.super.<init>scala#2719();
          ()
        };
        <method> <deferred> <stable> <accessor> <triedcooking> def self#13466: <empty>#3.this.N#7352;
        <method> <deferred> <stable> <accessor> def n#13467: M#7353.this.self#13466.type
      };
      class C#7354 extends M#7353 with <empty>#3.this.N#7352 {
        <method> <stable> <accessor> <triedcooking> def self#15016: <empty>#3.this.N#7352 = C#7354.this.self #15015;
        <triedcooking> private[this] val self #15015: <empty>#3.this.N#7352 = _;
        <method> <stable> <accessor> def n#15018: C#7354.this.self#7442.type = C#7354.this.n #15017;
        <triedcooking> private[this] val n #15017: C#7354.this.self#7442.type = _;
        <method> <mutable> <accessor> <triedcooking> def N$_setter_$self_$eq#15019(x$1#15021: <empty>#3.this.N#7352): scala#23.this.Unit#2340 = C#7354.this.self #15015 = x$1#15021;
        <method> <mutable> <accessor> <triedcooking> def N$_setter_$n_$eq#15022(x$1#15025: C#7354.this.self#7442.type): scala#23.this.Unit#2340 = C#7354.this.n #15017 = x$1#15025;
        <method> def <init>#14997(): <empty>#3.this.C#7354 = {
          C#7354.super.<init>#13465();
          ()
        }
      }
    }

    [running phase pickler on dependent_rebind.scala]
    [running phase refchecks on dependent_rebind.scala]
    test/files/trait-defaults/dependent_rebind.scala:16: error: overriding field n#15049 in trait N#7352 of type C#7354.this.self#15016.type;
     value n #15017 has incompatible type;
     found   : => C#7354.this.self#7442.type (with underlying type => C#7354.this.self#7442.type)
     required: => N#7352.this.self#7442.type
    class C extends M with N
          ^

    pos/t9111-inliner-workaround revealed need for:
-  override def transformInfo(sym: Symbol, tp: Type): Type = synthFieldsAndAccessors(tp)
+  override def transformInfo(sym: Symbol, tp: Type): Type = if (!sym.isJavaDefined) synthFieldsAndAccessors(tp) else tp

commit b56ca2f
Author: Adriaan Moors <[email protected]>
Date:   6 weeks ago

    static forwarders & private[this] val in trait

    object Properties extends PropertiesTrait

    trait PropertiesTrait {
      // the protected member is not emitted as a static member of  -- it works when dropping the access modifier
      // somehow, the module class member is considered deferred in BForwardersGen
      protected val propFilename: String = /
    }

    // [log jvm] No forwarder for 'getter propFilename' from Properties to 'module class Properties': false || m.isDeferred == true || false || false

    // the following method is missing compared to scalac
    // public final class Properties {
    //     public static String propFilename() {
    //         return Properties$.MODULE$.propFilename();
    //     }

    trait Chars {
      private[this] val char2uescapeArray = Array[Char]('\', 'u', 0, 0, 0, 0)
    }

    object Chars extends Chars

    // +++ w/reflect/scala/reflect/internal/Chars$.class
    // -  private final [C scala83014char2uescapeArray

    constant fold in forwarder for backwards compat
    constant-typed final val in trait should yield impl method

    bean{setter,getter} delegates to setter/getter (commit 1655d1b)

Author: adriaanm

src/compiler/scala/tools/nsc/Global.scala

@@ -461,10 +461,18 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
     val runsRightAfter = None
   } with ExtensionMethods
 
+  // phaseName = "fields"
+  object fields extends {
+    val global: Global.this.type = Global.this
+    // somewhere between typers, before erasure (so we get bridges for getters) and pickler (separate compilation of trait with fields and subclass)
+    val runsAfter = List("extmethods")
+    val runsRightAfter = None
+  } with Fields
+
   // phaseName = "pickler"
   object pickler extends {
     val global: Global.this.type = Global.this
-    val runsAfter = List("extmethods")
+    val runsAfter = List("fields")
     val runsRightAfter = None
   } with Pickler
 
@@ -608,7 +616,7 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
    *  This implementation creates a description map at the same time.
    */
   protected def computeInternalPhases(): Unit = {
-    // Note: this fits -Xshow-phases into 80 column width, which it is
+    // Note: this fits -Xshow-phases into 80 column width, which is
     // desirable to preserve.
     val phs = List(
       syntaxAnalyzer          -> "parse source into ASTs, perform simple desugaring",
@@ -618,6 +626,7 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
       patmat                  -> "translate match expressions",
       superAccessors          -> "add super accessors in traits and nested classes",
       extensionMethods        -> "add extension methods for inline classes",
+      fields                  -> "synthesize accessors and fields",
       pickler                 -> "serialize symbol tables",
       refChecks               -> "reference/override checking, translate nested objects",
       uncurry                 -> "uncurry, translate function values to anonymous classes",

src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala

@@ -158,7 +158,7 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
 
     def enclosingMethod(sym: Symbol): Option[Symbol] = {
       if (sym.isClass || sym == NoSymbol) None
-      else if (sym.isMethod) {
+      else if (sym.isMethod && !sym.isGetter) {
         if (doesNotExist(sym)) None else Some(sym)
       }
       else enclosingMethod(nextEnclosing(sym))

src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala

@@ -681,7 +681,7 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
       (((sym.rawflags & symtab.Flags.FINAL) != 0) || isTopLevelModuleClass(sym))
         && !sym.enclClass.isTrait
         && !sym.isClassConstructor
-        && !sym.isMutable // lazy vals and vars both
+        && (!sym.isMutable || nme.isTraitSetterName(sym.name)) // lazy vals and vars and their setters cannot be final, but trait setters are
       )
 
     // Primitives are "abstract final" to prohibit instantiation

src/compiler/scala/tools/nsc/transform/AddInterfaces.scala

@@ -35,6 +35,9 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
   def needsImplMethod(sym: Symbol) = (
        sym.isMethod
     && isInterfaceMember(sym)
+       // SYNTHESIZE_IMPL_IN_SUBCLASS accessors are mixed in by the fields phase, but others should be treated as regulars methods
+       // (this will eventually include constant-typed getters, as they can be fully implemented in the interface)
+    && (!(sym hasFlag ACCESSOR) || sym.isLazy || !(sym hasFlag SYNTHESIZE_IMPL_IN_SUBCLASS))
     && (!sym.hasFlag(DEFERRED | SUPERACCESSOR) || (sym hasFlag lateDEFERRED))
   )
 
@@ -79,7 +82,15 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
     val qual = Select(This(clazz), assignSym)
     if (assignSym.isSetter) Apply(qual, List(rhs))
     else Assign(qual, rhs)
-  }
+
+  private def isMemoizedTraitGetter(tree: Tree) = (tree.symbol hasFlag SYNTHESIZE_IMPL_IN_SUBCLASS) && tree.symbol.isGetter && !tree.symbol.info.resultType.isInstanceOf[ConstantType]
+
+  //  private def deriveMemberForInterface(tree: Tree): Tree =
+  //   if (isInterfaceTree(tree))
+  //     if (needsImplMethod(tree.symbol) || isMemoizedTraitGetter(tree)) DefDef(tree.symbol, EmptyTree) // TODO: use deriveDefDef(tree)(_ => EmptyTree) ?
+  //     else tree
+  //    else EmptyTree
+  // }
 
   /** Add calls to supermixin constructors
    *    `super[mix].$init$()`

src/compiler/scala/tools/nsc/transform/Constructors.scala

@@ -633,7 +633,9 @@ abstract class Constructors extends Statics with Transform with ast.TreeDSL {
           // The primary constructor is dealt with separately (we're massaging it here).
           case _: DefDef if statSym.isPrimaryConstructor || statSym.isMixinConstructor => ()
           case _: DefDef if statSym.isConstructor => auxConstructorBuf += stat
-          case _: DefDef => defBuf += stat
+          case stat: DefDef =>
+              defBuf += stat
+
 
           // If a val needs a field, an empty valdef goes into the template.
           // Except for lazy and ConstantTyped vals, the field is initialized by an assignment in:
@@ -643,7 +645,7 @@ abstract class Constructors extends Statics with Transform with ast.TreeDSL {
           case ValDef(mods, _, _, rhs) =>
             if (rhs ne EmptyTree) {
               val emitField = memoizeValue(statSym)
-              moveEffectToCtor(mods, rhs, if (emitField) statSym else NoSymbol)
+              moveEffectToCtor(mods, rhs, if (emitField) statSym else NoSymbol) // TODO: ever NoSymbol?
               if (emitField) defBuf += deriveValDef(stat)(_ => EmptyTree)
             } else defBuf += stat