bug#42672: 28.0.50; cl-defgeneric with :method generates incorrect Edebug symbols

bug#42672: 28.0.50; cl-defgeneric with :method generates incorrect Edebug symbols

[Philipp Stephani]

Create a file /tmp/defmethod.el:

$ cat /tmp/defmethod.el 
(cl-defgeneric foo (_)
  (:method ((_ number)) 1))

Visit the file in Emacs:

$ emacs -Q /tmp/defmethod.el

Instrument the `cl-defgeneric' form using C-u C-M-x.  The *Messages*
buffer now contains

Edebug: nil ((_ number))
Edebug: foo

The second line is for the generic function itself.  The first line,
however, is for the method defined by the `:method' form.  But its name
should be `foo ((_ number))', not `nil ((_ number))'.  This becomes a
problem if there are multiple such generic functions with different
names but identical signatures, because Edebug will then generate
duplicate symbols.  This breaks e.g. coverage instrumentation because
the instrumented frequencies will be attached to the wrong symbol.

Implementation-wise, I guess this is a problem with
`edebug-match-cl-generic-method-args'.  That function contains the
snippet

    ;; Append the arguments to edebug-def-name.
    (setq edebug-def-name
          (intern (format "%s %s" edebug-def-name args)))

However, `edebug-def-name' is only non-nil when using `cl-defmethod',
not when using `cl-defgeneric' with `:method'.


In GNU Emacs 28.0.50 (build 60, x86_64-pc-linux-gnu, GTK+ Version 3.24.18, cairo version 1.16.0)
 of 2020-08-02
Repository revision: 929e7e141c5780e51173fda7d7fc5b73411e4465
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux rodete

Recent messages:
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bug#42672: 28.0.50; cl-defgeneric with :method generates incorrect Edebug symbols

[Philipp Stephani]

Am So., 2. Aug. 2020 um 13:15 Uhr schrieb Philipp Stephani
<p.stephani2@gmail.com>:
>
>
> Create a file /tmp/defmethod.el:
>
> $ cat /tmp/defmethod.el
> (cl-defgeneric foo (_)
>   (:method ((_ number)) 1))
>
> Visit the file in Emacs:
>
> $ emacs -Q /tmp/defmethod.el
>
> Instrument the `cl-defgeneric' form using C-u C-M-x.  The *Messages*
> buffer now contains
>
> Edebug: nil ((_ number))
> Edebug: foo
>
> The second line is for the generic function itself.  The first line,
> however, is for the method defined by the `:method' form.  But its name
> should be `foo ((_ number))', not `nil ((_ number))'.  This becomes a
> problem if there are multiple such generic functions with different
> names but identical signatures, because Edebug will then generate
> duplicate symbols.  This breaks e.g. coverage instrumentation because
> the instrumented frequencies will be attached to the wrong symbol.
>
> Implementation-wise, I guess this is a problem with
> `edebug-match-cl-generic-method-args'.  That function contains the
> snippet
>
>     ;; Append the arguments to edebug-def-name.
>     (setq edebug-def-name
>           (intern (format "%s %s" edebug-def-name args)))
>
> However, `edebug-def-name' is only non-nil when using `cl-defmethod',
> not when using `cl-defgeneric' with `:method'.
>


The code in edebug.el is somewhat obscure, but I think one piece of
the problem is that `edebug-make-form-wrapper' unconditionally binds
`edebug-def-name' to nil, so such Edebug specifications don't really
work the way they are intended to work. There's some commented-out
binding of `edebug-containing-def-name' in that function, indicating
that the function is incomplete/buggy, and the corrected
implementation was intended to cover this case (and similar cases with
nested definitions such as `cl-flet').

bug#42672: 28.0.50; cl-defgeneric with :method generates incorrect Edebug symbols

[Philipp Stephani]

Am So., 2. Aug. 2020 um 13:15 Uhr schrieb Philipp Stephani
<p.stephani2@gmail.com>:
>
>
> Create a file /tmp/defmethod.el:
>
> $ cat /tmp/defmethod.el
> (cl-defgeneric foo (_)
>   (:method ((_ number)) 1))
>
> Visit the file in Emacs:
>
> $ emacs -Q /tmp/defmethod.el
>
> Instrument the `cl-defgeneric' form using C-u C-M-x.  The *Messages*
> buffer now contains
>
> Edebug: nil ((_ number))
> Edebug: foo
>
> The second line is for the generic function itself.  The first line,
> however, is for the method defined by the `:method' form.  But its name
> should be `foo ((_ number))', not `nil ((_ number))'.  This becomes a
> problem if there are multiple such generic functions with different
> names but identical signatures, because Edebug will then generate
> duplicate symbols.  This breaks e.g. coverage instrumentation because
> the instrumented frequencies will be attached to the wrong symbol.
>
> Implementation-wise, I guess this is a problem with
> `edebug-match-cl-generic-method-args'.  That function contains the
> snippet
>
>     ;; Append the arguments to edebug-def-name.
>     (setq edebug-def-name
>           (intern (format "%s %s" edebug-def-name args)))
>
> However, `edebug-def-name' is only non-nil when using `cl-defmethod',
> not when using `cl-defgeneric' with `:method'.

I've added a workaround (commit 3e0c3479b2). A more long-term solution
should ensure that the name of the `cl-defgeneric' function is part of
the method defined in this way.