Merge pull request #8428 from dotty-staging/fix-#7926

Fix #7926: Redo parameter aliasing optimization

Author: smarter

community-build/community-projects/stdLib213

@@ -90,6 +90,7 @@ class Compiler {
          new AugmentScala2Traits,    // Augments Scala2 traits with additional members needed for mixin composition.
          new ResolveSuper,           // Implement super accessors
          new FunctionXXLForwarders,  // Add forwarders for FunctionXXL apply method
+         new ParamForwarding,        // Add forwarders for aliases of superclass parameters
          new TupleOptimizations,     // Optimize generic operations on tuples
          new ArrayConstructors) ::   // Intercept creation of (non-generic) arrays and intrinsify.
     List(new Erasure) ::             // Rewrite types to JVM model, erasing all type parameters, abstract types and refinements.

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -145,10 +145,6 @@ object Annotations {
     def deferredResolve(atp: Type, args: List[Tree])(implicit ctx: Context): Annotation =
       deferred(atp.classSymbol)(resolveConstructor(atp, args))
 
-    def makeAlias(sym: TermSymbol)(implicit ctx: Context): Annotation =
-      apply(defn.AliasAnnot, List(
-        ref(TermRef(sym.owner.thisType, sym.name, sym))))
-
     /** Extractor for child annotations */
     object Child {
 

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

@@ -780,7 +780,6 @@ class Definitions {
   @tu lazy val RefiningAnnotationClass: ClassSymbol = ctx.requiredClass("scala.annotation.RefiningAnnotation")
 
   // Annotation classes
-  @tu lazy val AliasAnnot: ClassSymbol = ctx.requiredClass("scala.annotation.internal.Alias")
   @tu lazy val AnnotationDefaultAnnot: ClassSymbol = ctx.requiredClass("scala.annotation.internal.AnnotationDefault")
   @tu lazy val BodyAnnot: ClassSymbol = ctx.requiredClass("scala.annotation.internal.Body")
   @tu lazy val ChildAnnot: ClassSymbol = ctx.requiredClass("scala.annotation.internal.Child")

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

@@ -296,7 +296,7 @@ object Flags {
   val (_, CaseAccessor @ _, _) = newFlags(25, "<caseaccessor>")
 
   /** A Scala 2x super accessor / an unpickled Scala 2.x class */
-  val (SuperAccessorOrScala2x @ _, Scala2SuperAccessor @ _, Scala2x @ _) = newFlags(26, "<superaccessor>", "<scala-2.x>")
+  val (SuperParamAliasOrScala2x @ _, SuperParamAlias @ _, Scala2x @ _) = newFlags(26, "<super-param-alias>", "<scala-2.x>")
 
   /** A method that has default params */
   val (_, DefaultParameterized @ _, _) = newFlags(27, "<defaultparam>")
@@ -371,8 +371,9 @@ object Flags {
   /** Symbol is a self name */
   val (_, SelfName @ _, _) = newFlags(54, "<selfname>")
 
-  /** An existentially bound symbol (Scala 2.x only) */
-  val (Scala2ExistentialCommon @ _, _, Scala2Existential @ _) = newFlags(55, "<existential>")
+  /** A Scala 2 superaccessor (only needed during Scala2Unpickling) /
+   *  an existentially bound symbol (Scala 2.x only) */
+  val (Scala2SpecialFlags @ _, Scala2SuperAccessor @ _, Scala2Existential @ _) = newFlags(55, "<existential>")
 
   /** Children were queried on this class */
   val (_, _, ChildrenQueried @ _) = newFlags(56, "<children-queried>")
@@ -439,10 +440,10 @@ object Flags {
   val FromStartFlags: FlagSet = commonFlags(
     Module, Package, Deferred, Method, Case,
     HigherKinded, Param, ParamAccessor,
-    Scala2ExistentialCommon, MutableOrOpen, Opaque, Touched, JavaStatic,
+    Scala2SpecialFlags, MutableOrOpen, Opaque, Touched, JavaStatic,
     OuterOrCovariant, LabelOrContravariant, CaseAccessor,
     Extension, NonMember, Implicit, Given, Permanent, Synthetic,
-    SuperAccessorOrScala2x, Inline, Macro)
+    SuperParamAliasOrScala2x, Inline, Macro)
 
   /** Flags that are not (re)set when completing the denotation, or, if symbol is
    *  a top-level class or object, when completing the denotation once the class
@@ -551,6 +552,7 @@ object Flags {
   val JavaProtected: FlagSet                 = JavaDefined | Protected
   val MethodOrLazy: FlagSet                  = Lazy | Method
   val MutableOrLazy: FlagSet                 = Lazy | Mutable
+  val MethodOrLazyOrMutable: FlagSet         = Lazy | Method | Mutable
   val LiftedMethod: FlagSet                  = Lifted | Method
   val LocalParam: FlagSet                    = Local | Param
   val LocalParamAccessor: FlagSet            = Local | ParamAccessor | Private
@@ -561,7 +563,7 @@ object Flags {
   val PrivateMethod: FlagSet                 = Method | Private
   val NoInitsInterface: FlagSet              = NoInits | PureInterface
   val NoInitsTrait: FlagSet                  = NoInits | Trait                                // A trait that does not need to be initialized
-  val ValidForeverFlags: FlagSet             = Package | Permanent | Scala2ExistentialCommon
+  val ValidForeverFlags: FlagSet             = Package | Permanent | Scala2SpecialFlags
   val TermParamOrAccessor: FlagSet           = Param | ParamAccessor
   val PrivateParamAccessor: FlagSet          = ParamAccessor | Private
   val PrivateOrSynthetic: FlagSet            = Private | Synthetic

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

@@ -354,12 +354,12 @@ object NameKinds {
   val InlineAccessorName: PrefixNameKind = new PrefixNameKind(INLINEACCESSOR, "inline$")
 
   val AvoidClashName: SuffixNameKind = new SuffixNameKind(AVOIDCLASH, "$_avoid_name_clash_$")
-  val CacheName = new SuffixNameKind(CACHE, "$_cache")
   val DirectMethodName: SuffixNameKind = new SuffixNameKind(DIRECT, "$direct") { override def definesNewName = true }
   val FieldName: SuffixNameKind = new SuffixNameKind(FIELD, "$$local") {
       override def mkString(underlying: TermName, info: ThisInfo) = underlying.toString
   }
   val ExtMethName: SuffixNameKind = new SuffixNameKind(EXTMETH, "$extension")
+  val ParamAccessorName: SuffixNameKind = new SuffixNameKind(PARAMACC, "$accessor")
   val ModuleClassName: SuffixNameKind = new SuffixNameKind(OBJECTCLASS, "$", optInfoString = "ModuleClass")
   val ImplMethName: SuffixNameKind = new SuffixNameKind(IMPLMETH, "$")
   val AdaptedClosureName: SuffixNameKind = new SuffixNameKind(ADAPTEDCLOSURE, "$adapted") { override def definesNewName = true }

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

@@ -34,7 +34,7 @@ object NameTags extends TastyFormat.NameTags {
   final val IMPLMETH = 32       // Used to define methods in implementation classes
                                 // (can probably be removed).
 
-  final val CACHE = 33          // Used as a cache for the rhs of an alias implicit.
+  final val PARAMACC = 33       // Used for a private parameter alias
 
   def nameTagToString(tag: Int): String = tag match {
     case UTF8 => "UTF8"
@@ -55,6 +55,8 @@ object NameTags extends TastyFormat.NameTags {
     case DIRECT => "DIRECT"
     case FIELD => "FIELD"
     case EXTMETH => "EXTMETH"
+    case IMPLMETH => "IMPLMETH"
+    case PARAMACC => "PARAMACC"
     case ADAPTEDCLOSURE => "ADAPTEDCLOSURE"
     case OBJECTCLASS => "OBJECTCLASS"
 

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

@@ -1485,6 +1485,11 @@ object SymDenotations {
     override def transformAfter(phase: DenotTransformer, f: SymDenotation => SymDenotation)(implicit ctx: Context): Unit =
       super.transformAfter(phase, f)
 
+    /** Set flag `flags` in current phase and in all phases that follow */
+    def setFlagFrom(phase: DenotTransformer, flags: FlagSet)(using Context): Unit =
+      setFlag(flags)
+      transformAfter(phase, sd => { sd.setFlag(flags); sd })
+
     /** If denotation is private, remove the Private flag and expand the name if necessary */
     def ensureNotPrivate(implicit ctx: Context): SymDenotation =
       if (is(Private))

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

@@ -682,6 +682,7 @@ class TreePickler(pickler: TastyPickler) {
       if (flags.is(StableRealizable)) writeModTag(STABLE)
       if (flags.is(Extension)) writeModTag(EXTENSION)
       if (flags.is(ParamAccessor)) writeModTag(PARAMsetter)
+      if (flags.is(SuperParamAlias)) writeModTag(PARAMalias)
       if (flags.is(Exported)) writeModTag(EXPORTED)
       assert(!(flags.is(Label)))
     }

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

@@ -644,6 +644,7 @@ class TreeUnpickler(reader: TastyReader,
           case EXTENSION => addFlag(Extension)
           case GIVEN => addFlag(Given)
           case PARAMsetter => addFlag(ParamAccessor)
+          case PARAMalias => addFlag(SuperParamAlias)
           case EXPORTED => addFlag(Exported)
           case OPEN => addFlag(Open)
           case PRIVATEqualified =>