As a concrete example, I think 'origin tracking should be ephemeral. Why would an 'origin property end up on quoted syntax? I'm not entirely sure, but I tried adding check on bytecode writing for a fresh `raco setup`, and it apparently happens, even in the bootstrapping phase.
At Sat, 05 Mar 2016 17:29:10 -0600, Vincent St-Amour wrote: > Right, I understand that. > > Are any syntax properties used as heavily as source locations, though? > > Vincent > > > > On Sat, 05 Mar 2016 17:23:01 -0600, > Robby Findler wrote: > > > > Our experience with the source location change suggests that there are > > many places where code is implicitly relying on syntax properties not > > being preserved in byte code. This entire thread is inspired by one > > such (errortrace performance), and I know that I fixed several > > lingering bugs like this in redex well after the initial change. > > (Those bugs manifested as poor source location reporting for errors in > > redex programs). That experience makes me think we should not preserve > > all properties. (I don't have a sense of what the performance costs > > would be, but we could measure that if we cared, I think.) > > > > Robby > > > > > > On Sat, Mar 5, 2016 at 5:16 PM, Vincent St-Amour > > <[email protected]> wrote: > > > 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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