Subject: 29.1; cl-defstruct'ed struct errors out in the constructor compiler macro if a slot is called "quote"

From: Kisaragi Hiu <[email-masked]>
Date: Tue, 9 Jan 2024 21:32:06 +0900

* The problem

If a struct is defined to have a slot called "quote", the constructor
will fail during the compiler macro phase.

     (require 'cl-lib)
     (cl-defstruct my-test quote)
     (make-my-test :quote "'") ; error: (invalid-function "'")

     (put 'make-my-test 'compiler-macro nil) ; disable the compiler macro
     (make-my-test :quote "'") ; => #s(test "'")

I have tested Emacs 25.3, 26.3, 27.2, 28.2, and 29.1; this error is in
all these versions.

* Why this is a bug

This feels like a bug to me, because it's not clear that this would be
an unsupported use case, and because of the inconsistent behavior
between the constructor being inlined vs. without a compiler macro.

* Potential directions

This could be "fixed" by either digging into cl-defstruct and cl-lib
then fixing it properly, or by simply declaring in the documentation
that this is not supported. I wish for a proper fix, but the
documentation workaround also seems fine to me.

* Additional info

This is what the compiler macro for make-my-test expands into:

     (cl-block make-my-test
       (record
        ("'" my-test)
        "'"))

In GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
cairo version 1.17.8)
Windowing system distributor 'The X.Org Foundation', version 11.0.12101010
System Description: Arch Linux