Support inferring precise types for non-overriding members declared as tracked

Author: KacperFKorban

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

@@ -2842,9 +2842,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   }
 
   private def setAbstractTrackedInfo(sym: Symbol, rhs: Tree, tpt: untpd.Tree)(using Context): Unit =
-    if sym.allOverriddenSymbols.exists(_.flags.is(Tracked)) && !sym.flags.is(ParamAccessor) && !sym.flags.is(Param) then
-      sym.setFlag(Tracked)
-      if tpt.isEmpty then
+    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 =

tests/pos/abstract-tracked.scala

@@ -2,39 +2,49 @@ import scala.language.experimental.modularity
 import scala.language.future
 
 trait F:
-  tracked val x: Int
+  tracked val a: Int
 
 trait G:
-  tracked val y: Int
+  tracked val b: Int
 
 trait H:
-  tracked val z: Int = 3
+  tracked val c: Int = 3
 
 trait I extends F
 
 trait J extends F:
-  val x: Int = 1
+  val a: Int = 1
 
-class K(tracked val x: Int)
+class K(tracked val d: Int)
+
+class L
+
+trait M:
+  val f: Int
 
 object Test:
-  // val f : F(1) /*: F { val x: 1 }*/ = new F:
-  //   val x: 1 = 1
   val f = new F:
-    val x = 1
+    val a = 1
   val g = new G:
-    val y: 2 = 2
+    val b: 2 = 2
   val h = new H:
-    override val z = 4
+    override val c = 4
   val i = new I:
-    val x = 5
+    val a = 5
   val j = new J:
-    override val x = 6
+    override val a = 6
   val k = new K(7)
-
-  summon[f.x.type <:< 1]
-  summon[g.y.type <:< 2]
-  summon[h.z.type <:< 4]
-  summon[i.x.type <:< 5]
-  summon[j.x.type <:< 6]
-  summon[k.x.type <:< 7]
+  val l = new L {
+    tracked val e = 8
+  }
+  val m = new M:
+    tracked val f = 9
+
+  summon[f.a.type <:< 1]
+  summon[g.b.type <:< 2]
+  summon[h.c.type <:< 4]
+  summon[i.a.type <:< 5]
+  summon[j.a.type <:< 6]
+  summon[k.d.type <:< 7]
+  // summon[l.e.type <:< 8] // unrelated issue -- error: e is not a member of L
+  summon[m.f.type <:< 9]