Ok, yes, I evaluated ada-mode.el from 5.3.1 when I started emacs with emacs -Q, which loaded ada-mode 4.0.0.
M-x package-initialise and then opening a new ada file didn't load 5.3.1--I'm not sure what I did wrong.
Also that message wasn't in the messages buffer, I did check.
Is there anything else I can provide on this? When I evaluate 5.3.1 and then use debug-on-error mode and start ada-mode it hits the regexp line complaining about the wrong type:
Debugger entered--Lisp error: (wrong-type-argument sequencep "\\<\\(a\\(?:b\\(?:ort\\|s\\(?:tract\\)?\\)\\|cce\\(?:pt\\|ss\\)\\|l\\(?:iased\\|l\\)\\|nd\\|rray\\|t\\)\\|b\\(?:egin\\|ody\\)\\|c\\(?:ase\\|onstant\\)\\|d\\(?:e\\(?:clare\\|l\\(?:ay\\|ta\\)\\)\\|igits\\|o\\)\\|e\\(?:ls\\(?:e\\|if\\)\\|n\\(?:d\\|try\\)\\|x\\(?:ception\\|it\\)\\)\\|f\\(?:or\\|unction\\)\\|g\\(?:eneric\\|oto\\)\\|i[fns]\\|l\\(?:imited\\|oop\\)\\|mod\\|n\\(?:ew\\|ot\\|ull\\)\\|o\\(?:thers\\|ut\\|[fr]\\)\\|p\\(?:ackage\\|r\\(?:agma\\|ivate\\|o\\(?:cedure\\|tected\\)\\)\\)\\|r\\(?:a\\(?:\\(?:is\\|ng\\)e\\)\\|e\\(?:cord\\|m\\|names\\|queue\\|turn\\|verse\\)\\)\\|s\\(?:e\\(?:lect\\|parate\\)\\|ubtype\\)\\|t\\(?:a\\(?:gged\\|sk\\)\\|erminate\\|hen\\|ype\\)\\|u\\(?:ntil\\|se\\)\\|w\\(?:h\\(?:en\\|ile\\)\\|ith\\)\\|xor\\)\\>")
sort("\\<\\(a\\(?:b\\(?:ort\\|s\\(?:tract\\)?\\)\\|cce\\(?:pt\\|ss\\)\\|l\\(?:iased\\|l\\)\\|nd\\|rray\\|t\\)\\|b\\(?:egin\\|ody\\)\\|c\\(?:ase\\|onstant\\)\\|d\\(?:e\\(?:clare\\|l\\(?:ay\\|ta\\)\\)\\|igits\\|o\\)\\|e\\(?:ls\\(?:e\\|if\\)\\|n\\(?:d\\|try\\)\\|x\\(?:ception\\|it\\)\\)\\|f\\(?:or\\|unction\\)\\|g\\(?:eneric\\|oto\\)\\|i[fns]\\|l\\(?:imited\\|oop\\)\\|mod\\|n\\(?:ew\\|ot\\|ull\\)\\|o\\(?:thers\\|ut\\|[fr]\\)\\|p\\(?:ackage\\|r\\(?:agma\\|ivate\\|o\\(?:cedure\\|tected\\)\\)\\)\\|r\\(?:a\\(?:\\(?:is\\|ng\\)e\\)\\|e\\(?:cord\\|m\\|names\\|queue\\|turn\\|verse\\)\\)\\|s\\(?:e\\(?:lect\\|parate\\)\\|ubtype\\)\\|t\\(?:a\\(?:gged\\|sk\\)\\|erminate\\|hen\\|ype\\)\\|u\\(?:ntil\\|se\\)\\|w\\(?:h\\(?:en\\|ile\\)\\|ith\\)\\|xor\\)\\>" string-lessp)
regexp-opt("\\<\\(a\\(?:b\\(?:ort\\|s\\(?:tract\\)?\\)\\|cce\\(?:pt\\|ss\\)\\|l\\(?:iased\\|l\\)\\|nd\\|rray\\|t\\)\\|b\\(?:egin\\|ody\\)\\|c\\(?:ase\\|onstant\\)\\|d\\(?:e\\(?:clare\\|l\\(?:ay\\|ta\\)\\)\\|igits\\|o\\)\\|e\\(?:ls\\(?:e\\|if\\)\\|n\\(?:d\\|try\\)\\|x\\(?:ception\\|it\\)\\)\\|f\\(?:or\\|unction\\)\\|g\\(?:eneric\\|oto\\)\\|i[fns]\\|l\\(?:imited\\|oop\\)\\|mod\\|n\\(?:ew\\|ot\\|ull\\)\\|o\\(?:thers\\|ut\\|[fr]\\)\\|p\\(?:ackage\\|r\\(?:agma\\|ivate\\|o\\(?:cedure\\|tected\\)\\)\\)\\|r\\(?:a\\(?:\\(?:is\\|ng\\)e\\)\\|e\\(?:cord\\|m\\|names\\|queue\\|turn\\|verse\\)\\)\\|s\\(?:e\\(?:lect\\|parate\\)\\|ubtype\\)\\|t\\(?:a\\(?:gged\\|sk\\)\\|erminate\\|hen\\|ype\\)\\|u\\(?:ntil\\|se\\)\\|w\\(?:h\\(?:en\\|ile\\)\\|ith\\)\\|xor\\)\\>" t)
(concat "\\<" (regexp-opt ada-keywords t) "\\>")
(list (concat "\\<" (regexp-opt ada-keywords t) "\\>") '(0 font-lock-keyword-face))
(list (list (concat "\\<" (regexp-opt ada-keywords t) "\\>") '(0 font-lock-keyword-face)))
ada-font-lock-keywords()
font-lock-eval-keywords(ada-font-lock-keywords)
font-lock-set-defaults()
font-lock-mode-internal(t)
font-lock-default-function(t)
font-lock-mode()
turn-on-font-lock()
turn-on-font-lock-if-desired()
global-font-lock-mode-enable-in-buffers()
run-hooks(after-change-major-mode-hook)
run-mode-hooks(ada-mode-hook)
ada-mode()
funcall-interactively(ada-mode)
call-interactively(ada-mode record nil)
command-execute(ada-mode record)
execute-extended-command(nil "ada-mode" "ada-mode")
funcall-interactively(execute-extended-command nil "ada-mode" "ada-mode")
call-interactively(execute-extended-command nil nil)
command-execute(execute-extended-command)