     @differentiable(reverse)
     get { x }
 
-    // FIXME(SR-13096)
+    // FIXME: https://github.com/apple/swift/issues/55542
     // @differentiable(reverse)
     // set { stored = newValue }
   }

    fatalError()
  }

  // FIXME(SR-13096)
  // @derivative(of: subscript.set)
  // public func vjpSubscriptSetter(_ x: Float, _ newValue: Float) -> (
  //   value: (), pullback: (inout TangentVector) -> (Float, Float)

  }
}

// https://github.com/apple/swift/issues/56264
// Dispatch thunks and method descriptor mangling.
public protocol P: Differentiable {
  @differentiable(reverse, wrt: self)
  @differentiable(reverse, wrt: (self, x))
