let definitions can be accessible to run outside of their intended scope

[TheBizzle]

to setup
  if true [
    let a 2
  ]
  carefully [
    run "print a"
  ] [
    print error-message
  ]
end

• Steps to reproduce: Run setup, using the code above
• What should happen: Printing an error message
• What actually happens: Printing 2

a should only be scoped to its if block. It seems as if it is getting lifted up to the entire procedure's context, and remains accessible in the run's context.

This strikes me as a minor issue. It's not clear that anyone has a real model that is broken by this. Any problems should be easy for users to work around by renaming a variable or two.

The issue affects both desktop and NLW. Issue #24 seems semi-related. Reported by user tiaotiao on the NetLogo Forum.