`Inhabited` deriver gives error due to ambiguous types

Prerequisites

Please put an X between the brackets as you perform the following steps:

• Check that your issue is not already filed:
  https://github.com/leanprover/lean4/issues
• Reduce the issue to a minimal, self-contained, reproducible test case.
  Avoid dependencies to Mathlib or Batteries.
• Test your test case against the latest nightly release, for example on
  https://live.lean-lang.org/#project=lean-nightly
  (You can also use the settings there to switch to “Lean nightly”)

Description

The Inhabited deriver doesn't seem to use absolute names while generating the necessary instances, resulting in an error ambiguous, possible interpretations in the case of ambiguous type names. This is admittedly an edge case and low priority to fix.

Steps to Reproduce

Create a new lake project InheritedBug with a file InheritedBug/Basic containing

namespace MyNamespace

structure MyStruct where
  tag : Bool

and the following root file

import InheritedBug.Basic

open MyNamespace

structure MyStruct where
  tag : Bool
  deriving Inhabited

The error will occur on the last line of that file.

Reproduce the ambiguity using InheritedBug/Basic and the root file shown in the issue, then inspect how the Inhabited deriver generates instances for the second MyStruct. Done means the minimal project compiles without the “ambiguous, possible interpretations” error while preserving the demonstrated namespaced and root-level structures.