Re: [BUG] Eval sets incorrect runtime metainformation

[Philip McGrath <philip@philipmcgrath.com>]

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On 6/26/24 07:41, Andrew Tropin wrote:>
>>> That said, the evaluator does attach so-called "meta-data" information
>>> to procedures, such as the procedure name.
>>> https://www.gnu.org/software/guile/manual/html_node/Procedure-Properties.html.
>>> If you know that you are making a procedure you can insert some
>>> meta-data for use by your run-time, in an initial vector alist.  See
>>> https://www.gnu.org/software/guile/manual/html_node/Procedure-Properties.html.
>>> But that's limited and doesn't take macros, etc into account.
> 
> Yep, that's is why I wrote:
> 
> --8<---------------cut here---------------start------------->8---
> The another related problem is that the metainformation is stored in
> prodecures properties, but not in variables, which makes it impossible
> to implement a proper goto definition in general case.
> --8<---------------cut here---------------end--------------->8---
> 
> How hard is to make a generic metainformation, which is attachable to
> macros, symbols and other objects of the language, not only to
> procedures?
> 

Instead of run-time reflection on values, I think an IDE implementing 
jump to definition should use source location and binding information 
from syntax objects. That's how DrRacket does it.

The attached DrRacket screenshot (of [1]), in which I've tacked a bunch 
of binding arrows, shows how local definitions and complex 
macro-introduced binding structures are supported. It also works across 
modules, even with renaming: in the program `#lang racket (define one 
1)`, right-clicking on `define` and choosing "Jump to Binding 
Occurrence" will highlight `racket`, because the initial import of the 
racket language establishes the applicable binding of define, whereas 
choosing "Open Defining File" will open the racket/private/kw module, 
and then choosing "Jump to Definition (in Other File)" will jump to the 
definition of `new-define` on line 1171 of kw.rkt, which is renamed 
elsewhere to become the `define` of `#lang racket`.

Since syntax objects from the expander encode all the details of scope, 
this works mostly automatically. DrRacket makes this functionality 
available as a library, so navigation features can also be used from 
Emacs with racket-xp-mode [2] or other editors with the Language Server 
Protocol [3].

That said, if you do want to associate extra information with values at 
runtime, Guile has object properties [4], or of course you could always 
keep your own hash table on the side.

Philip

[1]: 
https://github.com/racket/racket/blob/6105332045595f8324985d7a34acc68fa5a61dcf/pkgs/racket-test/tests/json/indent.rkt#L244-L276
[2]: https://www.racket-mode.com/#racket_002dxp_002dmode
[3]: https://github.com/jeapostrophe/racket-langserver/
[4]: 
https://www.gnu.org/software/guile/manual/html_node/Object-Properties.html

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