Incorrect "Unused local variable" inspection

[szhorvat]

The "Unused local variable" inspection sometimes triggers incorrectly for a Module variable that is used as a value (i.e. right-hand-side of =) in the variable list of a second enclosed Module.

Code to reproduce it (probably not quite minimal, but almost):

fun[opt : OptionsPattern[]] :=
    Module[{options = Association@Flatten[{opt}]},
      Module[{foo = options["boo"]},
        foo
      ]
    ]

Screenshot:

---

Update with shorter examples.

The following trigger the inspection incorrectly:

Module[{b},
  Module[{a = b},
    a; b
  ]
]

Block[{b},
  Block[{a = b},
    a
  ]
]

The following do not trigger the inspection:

Function[b,
  Module[{a = b},
    a
  ]
]

Block[{b},
  Module[{a = b},
    a
  ]
]

The inner and the outer localizing construct must be the same for the inspection to trigger.

[halirutan]

Yep, when shit hits the fan... This will take another session to fix, but I identified the problem.