From 5943ca417c5930b082f31ec647975ce314c47a5c Mon Sep 17 00:00:00 2001
From: "Paul M. Rodriguez" <prodriguez@grammatech.com>
Date: Wed, 13 Mar 2024 16:19:16 -0500
Subject: [PATCH] Preserve unused variable warnings in and-let*

---
 binding.lisp       | 18 ++++++++++++------
 tests/binding.lisp |  7 +++++++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/binding.lisp b/binding.lisp
index 3aa0f93a..3c9815d6 100644
--- a/binding.lisp
+++ b/binding.lisp
@@ -290,12 +290,18 @@ Also, this version makes the bindings immutable."
                   ((list* (and var (type symbol)) clauses)
                    `(and ,var ,@(expand clauses body)))
                   ((list* (list var expr) clauses)
-                   (multiple-value-bind (local other)
-                       (partition-declarations (list var) decls env)
-                     `(let1 ,var ,expr
-                        ,@local
-                        (and ,var ,@(expand clauses
-                                            (append other body))))))
+                   (let ((temp (gensym (string var))))
+                     (multiple-value-bind (local-decls other-decls)
+                         (partition-declarations (list var) decls env)
+                       ;; The use of the temporary here is so we still
+                       ;; get style warnings if the variable is
+                       ;; unused.
+                       `(let* ((,temp ,expr)
+                               (,var ,temp))
+                          ,@local-decls
+                          (and ,temp
+                               ,@(expand clauses
+                                         (append other-decls body)))))))
                   ((list* (list expr) clauses)
                    `(and ,expr ,@(expand clauses body)))))))
       (car (expand clauses body)))))
diff --git a/tests/binding.lisp b/tests/binding.lisp
index f321a74b..2695f1e0 100644
--- a/tests/binding.lisp
+++ b/tests/binding.lisp
@@ -160,3 +160,10 @@
     (expect  '(let ((x 0)) (and-let* (x (y (- x 1)) ((plusp y))) (/ x y))) nil)
     (expect  '(let ((x nil)) (and-let* (x (y (- x 1)) ((plusp y))) (/ x y))) nil)
     (expect  '(let ((x 3)) (and-let* (x (y (- x 1)) ((plusp y))) (/ x y))) (/ 3 2))))
+
+#+(or sbcl ccl)
+(test and-let-unused ()
+  (signals style-warning
+    (eval `(and-let* ((x 1)
+                      (y 2))
+             x))))