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Re: Lambda in macrolet becomes a closure? (another breaking change in em

From: Stefan Monnier
Subject: Re: Lambda in macrolet becomes a closure? (another breaking change in emacs:))
Date: Fri, 23 Sep 2016 15:03:39 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux)

> and it seems to work well,  but
> (setq lexical-binding nil)
> (let* ((fu #'(lambda (a) (+ a 1)))
>                ba)
>           (message "%s" `,fu)
>           (let (byte-compile-warnings)
>            (setq ba (byte-compile `(lambda (b) (funcall (quote ,fu) b)))))
>          (funcall ba 2))
>  results in a *Compile-Log* buffer pop up with
> Warning: (lambda (a) ...) quoted with ' rather than with #'

Notice it says "warning", not "error".

> So (if I understend correctly) I can not predict that the value of the `fu'
> will be a (closure ...) or a (lambda ...),

Or any other object that can be passed to `funcall`, indeed.

> then how I can decide how to quote this value or silence the warning?

If you're worried about the warning, silence it with
`with-no-warnings`, since in this particular case you know that the
(lambda ()...) is a function *value* and not a function expression,
hence the warning is incorrect.

We could *fix* the warning once and for all by changing the
implementation of the `function` special form so that it just always
returns a (closure ...), so that (lambda ...) is only ever used as
a source code expression and never as a function value.  I think it
would be a good change, but I expect lots of people would complain about
such a gratuitous change.


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