Warn about arity errors in inlining calls (bug#12299)

Wrong number of arguments in inlining function calls (to `defsubst` or
explicitly using `inline`) did not result in warnings, or in very
cryptic ones.

* lisp/emacs-lisp/byte-opt.el (byte-compile-inline-expand): Add calls
to `byte-compile--check-arity-bytecode`.
* lisp/emacs-lisp/bytecomp.el (byte-compile-emit-callargs-warn)
(byte-compile--check-arity-bytecode): New functions.
(byte-compile-callargs-warn): Use factored-out function.
* test/lisp/emacs-lisp/bytecomp-resources/warn-callargs-defsubst.el:
* test/lisp/emacs-lisp/bytecomp-tests.el ("warn-callargs-defsubst.el"):
New test case.

1 files changed, 4 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 341643c7d16..ad9f827171a 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -274,6 +274,7 @@ Earlier variables shadow later ones with the same name.")
       ((pred byte-code-function-p)
        ;; (message "Inlining byte-code for %S!" name)
        ;; The byte-code will be really inlined in byte-compile-unfold-bcf.
+       (byte-compile--check-arity-bytecode form fn)
        `(,fn ,@(cdr form)))
       ((or `(lambda . ,_) `(closure . ,_))
        ;; While byte-compile-unfold-bcf can inline dynbind byte-code into
@@ -300,7 +301,9 @@ Earlier variables shadow later ones with the same name.")
                ;; surrounded the `defsubst'.
                (byte-compile-warnings nil))
            (byte-compile name))
-         `(,(symbol-function name) ,@(cdr form))))
+         (let ((bc (symbol-function name)))
+           (byte-compile--check-arity-bytecode form bc)
+           `(,bc ,@(cdr form)))))
 
       (_ ;; Give up on inlining.
        form))))