bug#33199: lambda forms are not self-quoting

[Noam Postavsky <npostavs@gmail.com>]

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Eli Zaretskii <eliz@gnu.org> writes:

> This removes useful information, IMO.

What's it really useful for though?  IMO, all anyone needs to know is
that (lambda ...) evaluates to a function.

> I'd be much happier if we added to the existing docs that lambda is
> not self-quoting in the lexical-binding environment, and described
> (and explained) what does happen in the lexical-binding environment.

It seems to me like too much useless detail, but if you insist.


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From bd397a3cec219a453e3118cb59e5955f5a09b870 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Mon, 29 Oct 2018 19:01:07 -0400
Subject: [PATCH v2] Note that lambda forms are not self-quoting under lex
 binding

* doc/lispref/functions.texi (Anonymous Functions):
* lisp/subr.el (lambda): Note that under lexical binding it yields a
closure object (Bug#33199).
---
 doc/lispref/functions.texi |  9 ++++++---
 lisp/subr.el               | 13 +++++++------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/doc/lispref/functions.texi b/doc/lispref/functions.texi
index 9b8057080e..7f8a6fc40b 100644
--- a/doc/lispref/functions.texi
+++ b/doc/lispref/functions.texi
@@ -1082,15 +1082,18 @@ Anonymous Functions
 @var{args}, documentation string @var{doc} (if any), interactive spec
 @var{interactive} (if any), and body forms given by @var{body}.
 
-In effect, this macro makes @code{lambda} forms self-quoting:
-evaluating a form whose @sc{car} is @code{lambda} yields the form
-itself:
+Under dynamic binding, this macro effectively makes @code{lambda}
+forms self-quoting: evaluating a form whose @sc{car} is @code{lambda}
+yields the form itself:
 
 @example
 (lambda (x) (* x x))
      @result{} (lambda (x) (* x x))
 @end example
 
+Note that when evaluting under lexical binding the result is a closure
+object (@pxref{Closures}).
+
 The @code{lambda} form has one other effect: it tells the Emacs
 evaluator and byte-compiler that its argument is a function, by using
 @code{function} as a subroutine (see below).
diff --git a/lisp/subr.el b/lisp/subr.el
index 59f6949b21..d09789340f 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -93,12 +93,13 @@ def-edebug-spec
   `(put (quote ,symbol) 'edebug-form-spec (quote ,spec)))
 
 (defmacro lambda (&rest cdr)
-  "Return a lambda expression.
-A call of the form (lambda ARGS DOCSTRING INTERACTIVE BODY) is
-self-quoting; the result of evaluating the lambda expression is the
-expression itself.  The lambda expression may then be treated as a
-function, i.e., stored as the function value of a symbol, passed to
-`funcall' or `mapcar', etc.
+  "Return an anonymous function.
+Under dynamic binding, a call of the form (lambda ARGS DOCSTRING
+INTERACTIVE BODY) is self-quoting; the result of evaluating the
+lambda expression is the expression itself.  Under lexical
+binding, the result is a closure.  Regardless, the result is a
+function, i.e., it may be stored as the function value of a
+symbol, passed to `funcall' or `mapcar', etc.
 
 ARGS should take the same form as an argument list for a `defun'.
 DOCSTRING is an optional documentation string.
-- 
2.11.0