Reassignment to var considered mistaken for reassignment to val

[felixmulder]

package dotty.tools.util

import scala.collection.mutable

class Whatever[A] extends mutable.Set[A] {
  private[this] var count = 0
  count = 0
}

Fails with:

-- Error: local/set.scala:7:8 --------------------------------------------------
7 |  count = 0
  |  ^^^^^^^^^
  |  reassignment to val

[DarkDimius]

My guess:

• desugar has an ad-hoc optimization to not generate setter if field is private in class;
• something later in pipeline isn't aware of this optimization and gets screwed.

If it is the case, I propose to remove this adhoc optimization.

[smarter]

Scala never generates setters for private[this] var, I think this is an important optimization that shouldn't be dropped.

[felixmulder]

def setterNeeded =
+  (mods is Mutable) && ctx.owner.isClass //&& (!(mods is PrivateLocal) || (ctx.owner is Trait))
-  (mods is Mutable) && ctx.owner.isClass && (!(mods is PrivateLocal) || (ctx.owner is Trait))

This change does indeed "solve" it.

[odersky]

The problem is in fact hat we have an overloaded occurrence of the private[this] val count and an inherited count method. The assignment logic was not prepared to handle this case. I am on it.