> To be pedantic, those aren't type declarations.
They are values of optimization qualities and guide the compiler strategy.
> More importantly, the (un)safety of type declaration isn't predicated on any specific safety/speed settings. The mere use of a type declaration implies that the programmer certifies their accuracy inside its scope;
With an optimize quality 3 for SAFETY a compiler will not reduce safety, even though there are type declarations.
The Common Lisp standard REQUIRES that safety at 3 causes 'safe code':
http://www.lispworks.com/documentation/HyperSpec/Body/03_eaa...
Which usually means full runtime checks in interpreted and compiled code, calls, system calls, ...
> an additional optimize declaration is not required.
Sure you need to have the right compiler qualities set to see those effects of your type declarations.
LispWorks:
CL-USER 4 > (proclaim '(optimize (safety 3)))
NIL
CL-USER 5 > (defun foo (x)
(declare (string x))
(+ x 2))
FOO
CL-USER 6 > (compile 'foo)
FOO
NIL
NIL
CL-USER 7 > (foo 'bar)
Error: In + of (BAR 2) arguments should be of type NUMBER.
1 (continue) Return a value to use.
2 Supply a new first argument.
3 (abort) Return to top loop level 0.
Type :b for backtrace or :c to proceed.
Type :bug-form "" for a bug report template or :? for other options.
CL-USER 8 : 1 >
Oh, the LispWorks compiler has ignored the type declaration at safety 3. The runtime checks are still there. The code has the same safety as without a type declaration.