`protected` annotation is ignored when module system is active

Prerequisites

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• 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

module

structure A where

namespace A

protected def true : A := ⟨⟩

/--
error: Type mismatch
  true
has type
  A
but is expected to have type
  Bool
-/
#guard_msgs in
def foo : Bool := true

end A

The error goes away when removing the module.

Expected behavior: true resolves to Bool.true.

Actual behavior: true resolved to A.true.

Versions

nightly-2025-08-10

Impact

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Start by running the self-contained reproducer against the latest Lean nightly and compare behavior with and without the module declaration. Trace the name-resolution path for protected def true and verify that true resolves to Bool.true in foo; the issue is done when the #guard_msgs expectation passes with the module system active.