Merge pull request #53 from dotty-staging/mb/abstract-tracked-namer

Move tracked inference logic to `inferredResultType`

Author: KacperFKorban

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

@@ -480,7 +480,7 @@ object Flags {
    */
   val AfterLoadFlags: FlagSet = commonFlags(
     FromStartFlags, AccessFlags, Final, AccessorOrSealed,
-    Abstract, LazyOrTrait, SelfName, JavaDefined, JavaAnnotation, Transparent, Tracked)
+    Abstract, LazyOrTrait, SelfName, JavaDefined, JavaAnnotation, Transparent)
 
   /** A value that's unstable unless complemented with a Stable flag */
   val UnstableValueFlags: FlagSet = Mutable | Method

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -2016,6 +2016,11 @@ class Namer { typer: Typer =>
       paramFn: Type => Type,
       fallbackProto: Type
     )(using Context): Type =
+    /** Is this member tracked? This is true if it is marked as `tracked` or if
+     *  it overrides a `tracked` member. To account for the later, `isTracked`
+     *  is overriden to `true` as a side-effect of computing `inherited`.
+     */
+    var isTracked: Boolean = sym.is(Tracked)
 
     /** A type for this definition that might be inherited from elsewhere:
      *  If this is a setter parameter, the corresponding getter type.
@@ -2051,8 +2056,10 @@ class Namer { typer: Typer =>
               if paramss.isEmpty then info.widenExpr
               else NoType
 
-          val iRawInfo =
-            cls.info.nonPrivateDecl(sym.name).matchingDenotation(site, schema, sym.targetName).info
+          val iDenot = cls.info.nonPrivateDecl(sym.name).matchingDenotation(site, schema, sym.targetName)
+          val iSym = iDenot.symbol
+          if iSym.is(Tracked) then isTracked = true
+          val iRawInfo = iDenot.info
           val iResType = instantiatedResType(iRawInfo, paramss).asSeenFrom(site, cls)
           if (iResType.exists)
             typr.println(i"using inherited type for ${mdef.name}; raw: $iRawInfo, inherited: $iResType")
@@ -2141,6 +2148,7 @@ class Namer { typer: Typer =>
             if defaultTp.exists then TypeOps.SimplifyKeepUnchecked() else null)
         match
           case ctp: ConstantType if sym.isInlineVal => ctp
+          case tp if isTracked => tp
           case tp => TypeComparer.widenInferred(tp, pt, Widen.Unions)
 
     // Replace aliases to Unit by Unit itself. If we leave the alias in
@@ -2151,7 +2159,7 @@ class Namer { typer: Typer =>
     def lhsType = fullyDefinedType(cookedRhsType, "right-hand side", mdef.srcPos)
     //if (sym.name.toString == "y") println(i"rhs = $rhsType, cooked = $cookedRhsType")
     if (inherited.exists)
-      if sym.isInlineVal then lhsType else inherited
+      if sym.isInlineVal || isTracked then lhsType else inherited
     else {
       if (sym.is(Implicit))
         mdef match {

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2834,20 +2834,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       case rhs =>
         excludeDeferredGiven(rhs, sym):
           typedExpr(_, tpt1.tpe.widenExpr)
-    setAbstractTrackedInfo(sym, rhs1, tpt)
-    val tpt2 = if sym.flags.is(Tracked) && tpt.isEmpty && !sym.flags.is(ParamAccessor) && !sym.flags.is(Param) then TypeTree(rhs1.tpe) else tpt1
-    val vdef2 = assignType(cpy.ValDef(vdef)(name, tpt2, rhs1), sym)
-    postProcessInfo(vdef2, sym)
-    vdef2.setDefTree
+    val vdef1 = assignType(cpy.ValDef(vdef)(name, tpt1, rhs1), sym)
+    postProcessInfo(vdef1, sym)
+    vdef1.setDefTree
   }
-
-  private def setAbstractTrackedInfo(sym: Symbol, rhs: Tree, tpt: untpd.Tree)(using Context): Unit =
-    if !sym.flags.is(ParamAccessor) && !sym.flags.is(Param) then
-      if sym.allOverriddenSymbols.exists(_.flags.is(Tracked)) then
-        sym.setFlag(Tracked)
-      if sym.flags.is(Tracked) && tpt.isEmpty then
-        sym.info = rhs.tpe
-
   private def retractDefDef(sym: Symbol)(using Context): Tree =
     // it's a discarded method (synthetic case class method or synthetic java record constructor or overridden member), drop it
     val canBeInvalidated: Boolean =

tests/pos/abstract-tracked-2.scala

@@ -0,0 +1,11 @@
+import scala.language.experimental.modularity
+import scala.language.future
+
+abstract class Vec:
+  tracked val size: Int
+
+@main def main =
+  val v = new Vec:
+    val size0: size.type = 10
+    val size = 10
+    val size1: size.type = 10