Infer tracked for explicit type class witnesses

Author: KacperFKorban

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

@@ -1935,9 +1935,9 @@ class Namer { typer: Typer =>
       for params <- ddef.termParamss; param <- params do
         val psym = symbolOfTree(param)
         if needsTracked(psym, param, owningSym) then
-          psym.setFlag(Tracked)
           for acc <- sym.maybeOwner.infoOrCompleter.decls.lookupAll(psym.name) if acc.is(ParamAccessor) do
             acc.resetFlag(PrivateLocal)
+            psym.setFlag(Tracked)
             acc.setFlag(Tracked)
 
     if Feature.enabled(modularity) then addTrackedIfNeeded(ddef, sym.maybeOwner)
@@ -2019,7 +2019,7 @@ class Namer { typer: Typer =>
    */
   def isContextBoundWitnessWithAbstractMembers(psym: Symbol, param: ValDef, owningSym: Symbol)(using Context): Boolean =
     (owningSym.isClass || owningSym.isAllOf(Given | Method))
-    && param.hasAttachment(ContextBoundParam)
+    && (param.hasAttachment(ContextBoundParam) || psym.isOneOf(GivenOrImplicit))
     && psym.info.memberNames(abstractTypeNameFilter).nonEmpty
 
   extension (sym: Symbol)

tests/pos/infer-tracked-explicit-witness.scala

@@ -0,0 +1,18 @@
+import scala.language.experimental.modularity
+
+trait T:
+  type Self
+  type X
+  def foo: Self
+
+class D[C](using val wd: C is T)
+class E(using val we: Int is T)
+
+def Test =
+  given w: Int is T:
+    def foo: Int = 42
+    type X = Long
+  val d = D(using w)
+  summon[d.wd.X =:= Long]
+  val e = E(using w)
+  summon[e.we.X =:= Long]