Thank you for raising this issue, Christiaan! The current policy (very early class-op inlining) is a major difficulty and the main source of fragility in my compiling-to-categories implementation. I have a tediously programmed and delicately balanced collection of techniques to intercept and transform class ops to non-ops early and then transform back late for elimination, but it doesn't work in all situations. Since class operations roughly correspond to operations in various algebraic abstractions---interfaces with laws---I often want to exploit exactly those laws as rewrite rules, and yet those rules currently cannot be used dependably. - Conal
On Fri, Mar 6, 2020 at 7:22 AM Christiaan Baaij <[email protected]> wrote: > Hello, > > The other day I was experimenting with RULES and got this warning: > > src/Clash/Sized/Vector.hs:2159:11: warning: [-Winline-rule-shadowing] > Rule "map Pack" may never fire > because rule "Class op pack" for ‘pack’ might fire first > Probable fix: add phase [n] or [~n] to the competing rule > | > 2159 | {-# RULES "map Pack" map pack = id #-} > > The warning seems to suggests two things: > 1. "Class op" -> "dictionary projection" are implemented as rewrite rules > and executed the same way as other user-defined RULES > 2. These rules run first, and you cannot run anything before them > > Now my question is, is 1. actually true? or is that warning just a (white) > lie? > If 1. is actually true, would there be any objections to adding a "-1" > phase: where RULES specified to start from phase "-1" onward fire before > any of the Class op rules. > I'm quite willing to implement the above if A) Class op rules are actually > implemented as builtin RULES; B) there a no objections to this "-1" phase. > > Thanks, > Christiaan > > _______________________________________________ > ghc-devs mailing list > [email protected] > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs >
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