What would be use cases for ephemeral properties? I agree that most properties wouldn't need to be preserved, but I can't think of a case where we would want to explicitly not have a property be preserved.
That, and having two kinds of syntax properties would be potentially confusing. Your third solution does make the distinction pretty clear, but having a single kind would make the interface simpler. Vincent On Sat, 05 Mar 2016 16:23:00 -0600, Matthew Flatt wrote: > > I agree that both of those are potential issues. I'd expect problems, > but I don't know how common the problems would be. > > I think we would probably end up wanting ephemeral properties, anyway, > so it makes more sense to be to leave ephemeral as the default and add > a non-ephemeral option. > > At Sat, 5 Mar 2016 15:25:51 -0600, Robby Findler wrote: > > Is avoiding the change to preserve of all properties a backwards > > compatibility concern or a performance one? (I wouldn't ask, except > > there were a surprising number of bugfixes for the source location > > change.) > > > > Robby > > > > > > On Sat, Mar 5, 2016 at 8:09 AM, Matthew Flatt <[email protected]> wrote: > > > At Thu, 03 Mar 2016 11:00:23 -0600, Vincent St-Amour wrote: > > >> On Wed, 02 Mar 2016 22:23:29 -0600, > > >> Matthew Flatt wrote: > > >> > Instead of using the existence of a source location to determine where > > >> > to add instrumentation, debugging should be based on the details of the > > >> > source location. I'm not immediately sure of the right rule, but I'll > > >> > work on it. > > >> > > >> Would `syntax-original?` help here? > > > > > > This is sort of job that `syntax-original?` was intended for, but I > > > think it doesn't work well. > > > > > > For example, if you have > > > > > > (define-syntax-rule (m x) > > > (* (+ x 1) 2)) > > > > > > and you use `m` in the same module, then you want an error for a > > > non-numeric `x` to highlight `(+ x 1)`. (Since `m` doesn't guard > > > against a bad `x`, it's probably not intended as an abstraction.) A > > > `syntax-original?` test would limit highlighting to the uses of `m`. > > > > > > I think this line of thought and other experience with > > > `syntax-original?` is why we haven't used it in errortrace. > > > > > > > > > One alternative is to make errortrace add a syntax property to the > > > original program, and then then only instrument forms that have the > > > syntax property after expansion. That implements a notion of > > > "original?" that includes templates in the source program, and it would > > > be consistent with the old use of source locations to determine > > > "original?". > > > > > > DrRacket compiles files with errortrace instrumentation to bytecode, > > > and that suggests preserving the syntax property in bytecode. We don't > > > yet have a mechanism for designating new syntax properties for > > > preservation in bytecode, but it was just a matter of time... > > > > > > I see a few possible approaches to preserving syntax properties: > > > > > > * Add a parameter that lists keys to be preserved. The parameter's > > > default value would be `(list 'paren-shape)`. > > > > > > This approach would probably work well enough for DrRacket and > > > errortrace, because DrRacket could set the parameter while writing > > > errortrace-instrumented bytecode. It's easy to imagine uses of > > > syntax properties where that kind of configuration from the outside > > > is inconvenient, though. > > > > > > * Introduce a naming convention for symbols as syntax properties. For > > > example, a symbol that starts with the letters "preserved:" could > > > mean that the property should be preserved in bytecode. > > > > > > A naming convention is easy, and it doesn't require cooperation from > > > the tool that's writing bytecode. We'd still have to declare > > > 'paren-shape to be a special case. > > > > > > * Introduce a prefab structure and a convention that a key is > > > preserved if it is an instance. For example, the designated prefab > > > structure type could be > > > > > > (struct preserved (name) #:prefab) > > > > > > and then '#s(preserved errortrace) as a syntax-property key would be > > > preserved. > > > > > > To make this work, syntax-property keys would have to be compared > > > with `equal?` instead of `eq?`, but I think that change would be ok. > > > > > > Among these options, I'm leaning toward the last one. > > > > > > Any other ideas? > > > > > > -- > > > You received this message because you are subscribed to the Google Groups > > "Racket Developers" group. > > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [email protected]. > > > To post to this group, send email to [email protected]. > > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/racket-dev/56dae8b5.4e2b620a.62d8b.ffffc560SM > > TPIN_ADDED_MISSING%40gmr-mx.google.com. > > > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-dev/56db5c48.e9a2420a.265b2.09b9SMTPIN_ADDED_MISSING%40gmr-mx.google.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Developers" group. 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