records: Warn about shadowing due to inherited field value bindings.

This is a followup to a7c8e68dc51144a6d3981b770aca9c4897fc7c0c: this commit
introduced a new binding in the body of field values, which could silently
shadow outer bindings.  This new warning catches potentially unwanted
shadowing.

* guix/records.scm (make-syntactic-constructor)[check-shadowing]: New
procedure.
[wrap-field-value]: Use it.
* tests/records.scm ("define-record-type* & inherited value shadowing"): New
test.

Change-Id: I81ad14cf10da7213e9f8db987c8b0bd4c41acba2
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
Merges: #7424

1 files changed, 20 insertions, 0 deletions

diff --git a/tests/records.scm b/tests/records.scm
index 9c071334d50..57a21d2effc 100644
--- a/tests/records.scm
+++ b/tests/records.scm
@@ -302,6 +302,26 @@
         =>
         (,(foo-bar child) ,(foo-baz child))))))
 
+(test-assert "define-record-type* & inherited value shadowing"
+  (let ((exp '(begin
+                (define-record-type* <foo> foo make-foo
+                  foo?
+                  (bar foo-bar)
+                  (baz foo-baz (thunked)))
+
+                (let ((x (foo (bar 1) (baz 2)))
+                      (baz 123))
+                  ;; Below, the 'baz' binding for the inherited field value
+                  ;; shadows the 'baz' above, which should trigger a warning.
+                  (foo (inherit x)
+                       (baz (* baz 2)))))))
+    (string-contains
+     (call-with-output-string
+       (lambda (port)
+         (parameterize ((current-warning-port port))
+           (eval exp (test-module)))))
+     "shadows local variable")))
+
 (test-assert "define-record-type* & delayed"
   (begin
     (define-record-type* <foo> foo make-foo