import without warnings

[Alex Shinn]

Currently when you import from a module which hasn't
been required yet you get runtime warnings, like:

Warning: the following toplevel variables are referenced but unbound:

json#json-write (in json-write)
json#json-write (in json-write)

For implementing autoload it would be convenient to
be able to suppress this warning, such as with

(import-without-warning <import-spec>)

or

(import-unbound <import-spec>)

[felix winkelmann]

Here is a proposal for a solution:

(define-for-syntax unbound-in-eval '())

(define-syntax without-warnings
  (syntax-rules ()
    ((_ body ...)
     (begin
       (##core#elaborationtimeonly
	(set! unbound-in-eval ##sys#unbound-in-eval))
       (begin body ...)
       (##core#elaborationtimeonly   ; returns undefined value
	(set! ##sys#unbound-in-eval unbound-in-eval))))))  

The use of those internal forms is somewhat ugly, but we must make sure that the code is evaluated at expansion time without side-effecting a potentially generated import-lib (which would contain forms inside begin-for-syntax expressions, something we don't want).
Note the return value of (void) above.

The warnings are actually generated by the REPL, not by import.

[felix winkelmann]

Can you live with this solution? If yes, please consider closing the ticket.

[felix winkelmann]

I close this, since you seem to have forgotten about it.

[felix winkelmann]

Milestone 4.7.0 deleted

[felix winkelmann]

Milestone 4.8.0 deleted