this qualified field masked by argument

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I can't say definitively this is a bug. But I think it should be. There is only one thing which "this.x" can mean. It looks to me like this could be implemented with some extra logic in typedAssign.

class A(var x: Int)
class B(x: Int) extends A(x) { def update(z: Int) = this.x = z }

a.scala:2: error: reassignment to val
class B(x: Int) extends A(x) { def update(z: Int) = this.x = z }
                                                           ^
one error found

I would expect it to work like the common situation (common in java anyway) where one does:

def f(x: Int) = this.x = x

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Imported From: https://issues.scala-lang.org/browse/SI-3194?orig=1
Reporter: @paulp

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@odersky said:
I think this is fundamentally a duplicate of another ticket, but I can't find it right now. The problem is that the constructor parameter does get modelled as a private[this] field. For the duplicate I decided that this should wait until after 2.8 since changing it now would be too risky.

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@paulp said:
Replying to [comment:3 odersky]:

I think this is fundamentally a duplicate of another ticket, but I can't find it right now. The problem is that the constructor parameter does get modelled as a private[this] field. For the duplicate I decided that this should wait until after 2.8 since changing it now would be too risky.

That's fine - there's no ticket I open these days intending it to be addressed before 2.8 unless it involves planes falling out of the sky. I only open them so I don't forget.

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@paulp said:
See #3861 for a related issue and a workaround to this one. (TL/DR: give B a self-type of A.)

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@paulp said:
Here is another related issue. There does not seem to be any way to get this to compile without changing the name of the parameter in Foo.

trait Settings {
  type T = Int
  def f: T = 5
}

class Bar(val settings: Settings) { }

class Foo(settings: Settings) extends Bar(settings) {
  def g = settings.f
}

a.scala:9: error: private value settings escapes its defining scope as part of type Foo.this.settings.T
  def g = settings.f
      ^
one error found

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@paulp said:
Replying to [comment:5 extempore]:

See #3861 for a related issue and a workaround to this one. (TL/DR: give B a self-type of A.)

Now that #3861 is fixed, as one might suppose, the workaround no longer works around.

// This code compiles in 2.8.1 but not since whenever SI-3861 was fixed
// (tested at r24303.)
class A(var x: Int)
class B(x: Int) extends A(x) {
  self: A =>

  def update(z: Int) = this.x = z
}

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@paulp said:
See also #4606.

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@paulp said:
See also #4762.