bug#33164: 26.1; Compiled function information in *Help*

[Drew Adams <drew.adams@oracle.com>]

emacs -Q

C-h v region-extract-function tells me:

region-extract-function is a variable defined in 'simple.el'.
Its value is #f(compiled-function (method) #<bytecode 0x1001ae2e9>)
...

There is a link to `simple.el'.  And the #<bytecode...> is also a link,
to the disassembled byte-code.

This is a bit more helpful than what we had in Emacs 24 (which was the
byte-code, printed).

But it is less helpful than what we had back in Emacs 23, which printed
the name or the lambda expression of the function that is the value of
the variable.  Examples:

 comment-line-break-function is a variable defined in `simple.el'.
 Its value is comment-indent-new-line


 completion-annotate-function is a variable defined in `minibuffer.el'.
 Its value is (lambda (var)
                (and (custom-variable-p (intern-soft var))
                "  (option)"))

Such description provided lots of helpful information, and we've lost
that now.

I guess this comes from eager macroexpansion (?).  But is there no way
for our help system to know what the function name or original lambda
expression is, and print that?

Yes, it would be helpful for it to _also_ provide the info that the
value is actually the byte-compilation of that function, when that is
the case, and to provide a link to the disassembly of that byte-code.

But just showing the byte code, even disassembled, is not so helpful.
What if a user wants to go to the function definition, to use it as a
model for defining a new value for the variable or just to study it?

Our help system should not become _less_ helpful just because we find
ways to optimize Emacs or make other improvements.  From a help
perspective, this is a step backward for users.

But maybe I'm missing something?  Is there currently some way to get to
the source code defining the function that is the variable value?


In GNU Emacs 26.1 (build 1, x86_64-w64-mingw32)
 of 2018-05-30 built on CIRROCUMULUS
Repository revision: 07f8f9bc5a51f5aa94eb099f3e15fbe0c20ea1ea
Windowing system distributor 'Microsoft Corp.', version 10.0.16299