Use lexical-binding in check-declare.el and add tests

* lisp/emacs-lisp/check-declare.el: Use lexical-binding.
(check-declare-warn): Silence byte compiler warning about unused
lexical argument.

* test/lisp/emacs-lisp/check-declare-tests.el: New file with tests
for check-declare.el.

lisp/emacs-lisp/check-declare.el

@@ -1,4 +1,4 @@
-;;; check-declare.el --- Check declare-function statements
+;;; check-declare.el --- Check declare-function statements  -*- lexical-binding: t; -*-
 
 ;; Copyright (C) 2007-2020 Free Software Foundation, Inc.
 
@@ -248,7 +248,7 @@ TYPE is a string giving the nature of the error.
 Optional LINE is the claim's line number; otherwise, search for the claim.
 Display warning in `check-declare-warning-buffer'."
   (let ((warning-prefix-function
-         (lambda (level entry)
+         (lambda (_level entry)
 	   (insert (format "%s:%d:" (file-relative-name file) (or line 0)))
            entry))
         (warning-fill-prefix "    "))

test/lisp/emacs-lisp/check-declare-tests.el

@@ -0,0 +1,116 @@
+;;; check-declare-tests.el --- Tests for check-declare.el  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2020 Free Software Foundation, Inc.
+
+;; Author: Simen Heggestøyl <simenheg@gmail.com>
+;; Keywords:
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(require 'check-declare)
+(require 'ert)
+(eval-when-compile (require 'subr-x))
+
+(ert-deftest check-declare-tests-locate ()
+  (should (file-exists-p (check-declare-locate "check-declare" "")))
+  (should
+   (string-prefix-p "ext:" (check-declare-locate "ext:foo" ""))))
+
+(ert-deftest check-declare-tests-scan ()
+  (let ((file (make-temp-file "check-declare-tests-")))
+    (unwind-protect
+        (progn
+          (with-temp-file file
+            (insert
+             (string-join
+              '(";; foo comment"
+                "(declare-function ring-insert \"ring\" (ring item))"
+                "(let ((foo 'code)) foo)")
+              "\n")))
+          (let ((res (check-declare-scan file)))
+            (should (= (length res) 1))
+            (pcase-let ((`((,fnfile ,fn ,arglist ,fileonly)) res))
+              (should (string-match-p "ring" fnfile))
+              (should (equal "ring-insert" fn))
+              (should (equal '(ring item) arglist))
+              (should-not fileonly))))
+      (delete-file file))))
+
+(ert-deftest check-declare-tests-verify ()
+  (let ((file (make-temp-file "check-declare-tests-")))
+    (unwind-protect
+        (progn
+          (with-temp-file file
+            (insert
+             (string-join
+              '(";; foo comment"
+                "(defun foo-fun ())"
+                "(defun ring-insert (ring item)"
+                "\"Insert onto ring RING the item ITEM.\""
+                "nil)")
+              "\n")))
+          (should-not
+           (check-declare-verify
+            file '(("foo.el" "ring-insert" (ring item))))))
+      (delete-file file))))
+
+(ert-deftest check-declare-tests-verify-mismatch ()
+  (let ((file (make-temp-file "check-declare-tests-")))
+    (unwind-protect
+        (progn
+          (with-temp-file file
+            (insert
+             (string-join
+              '(";; foo comment"
+                "(defun foo-fun ())"
+                "(defun ring-insert (ring)"
+                "\"Insert onto ring RING the item ITEM.\""
+                "nil)")
+              "\n")))
+          (should
+           (equal
+            (check-declare-verify
+             file '(("foo.el" "ring-insert" (ring item))))
+            '(("foo.el" "ring-insert" "arglist mismatch")))))
+      (delete-file file))))
+
+(ert-deftest check-declare-tests-sort ()
+  (should-not (check-declare-sort '()))
+  (should (equal (check-declare-sort '((a (1 a)) (b (2)) (d (1 d))))
+                 '((2 (b)) (1 (a a) (d d))))))
+
+(ert-deftest check-declare-tests-warn ()
+  (with-temp-buffer
+    (let ((check-declare-warning-buffer (buffer-name)))
+      (check-declare-warn
+       "foo-file" "foo-fun" "bar-file" "it wasn't" 999)
+      (let ((res (buffer-string)))
+        ;; Don't care too much about the format of the output, but
+        ;; check that key information is present.
+        (should (string-match-p "foo-file" res))
+        (should (string-match-p "foo-fun" res))
+        (should (string-match-p "bar-file" res))
+        (should (string-match-p "it wasn't" res))
+        (should (string-match-p "999" res))))))
+
+(provide 'check-declare-tests)
+;;; check-declare-tests.el ends here