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[Chicken-hackers] [PATCH] Use current environment in code walkers, causi

From: Peter Bex
Subject: [Chicken-hackers] [PATCH] Use current environment in code walkers, causing "import" to be lexically scoped (fixes the remainder of #1437)
Date: Sat, 28 Apr 2018 23:17:27 +0200
User-agent: NeoMutt/20170113 (1.7.2)

Hi all,

While figuring out what was causing the remaining issue in #1437, I found
out that a proper fix would be to change the code walker to always
dereference ##sys#current-environment for every lookup.  Attached is a
pretty large, but straightforward patch to do this.

The patch basically drops the "se" argument of "walk" in both the
compiler and the interpreter.  Any procedure that requires a syntax
environment argument is now called with (##sys#current-environment),
and anywhere the syntax environment is (functionally) modified, we
parameterize (##sys#current-environment) before calling walk recursively.

As a cool side effect, the fix accidentally adds a new feature: (import)
is now lexically scoped (like Python's import, but better).

For instance,

  (let ()
    (import (rename scheme (- +)))
    (print (+ 1 2)))
  (print (+ 1 2)))

will now print "-1", followed by "3".


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