paper around `match' bug

* module/ice-9/match.scm (match): Always introduce a lexical binding, to
  avoid http://debbugs.gnu.org/9567.  Real fix ongoing.  Patch and
  original report by Stefan Israelsson Tampe.

* test-suite/tests/match.test: Add test.

module/ice-9/match.scm

@@ -57,3 +57,21 @@
 ;; Note: Make sure to update `match.test.upstream' when updating this
 ;; file.
 (include-from-path "ice-9/match.upstream.scm")
+
+(define-syntax match
+  (syntax-rules ()
+    ((match)
+     (match-syntax-error "missing match expression"))
+    ((match atom)
+     (match-syntax-error "no match clauses"))
+    ((match (app ...) (pat . body) ...)
+     (let ((v (app ...)))
+       (match-next v ((app ...) (set! (app ...))) (pat . body) ...)))
+    ((match #(vec ...) (pat . body) ...)
+     (let ((v #(vec ...)))
+       (match-next v (v (set! v)) (pat . body) ...)))
+    ((match atom (pat . body) ...)
+     (let ((v atom))
+       (match-next v (atom (set! atom)) (pat . body) ...)))
+    ))
+

test-suite/tests/match.test

@@ -102,6 +102,18 @@
         (('one ('two x) ('three y ('and z '(and 5))))
          (equal? (list x y z) '(2 3 4))))))
 
+  (pass-if "and, unique names"
+    (let ((tree '(1 2)))
+      (match tree
+        ((and (a 2) (1 b))
+         (equal? 3 (+ a b))))))
+  
+  (pass-if "and, same names"
+    (let ((a '(1 2)))
+      (match a
+        ((and (a 2) (1 b))
+         (equal? 3 (+ a b))))))
+  
   (with-test-prefix "records"
 
     (pass-if "all slots, bind"