experimental switch for generic compileTime, remove typeof behavior
#24230
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metagn
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typeof behaviortypeof behavior [backport:2.0]
metagn
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typeof behavior [backport:2.0]typeof behavior
Araq
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Oct 6, 2024
fixes #24228, refs #22022 As described in #24228 (comment), instantiating generic routines inside `typeof` causes all code inside to be treated as being in a typeof context, and thus preventing compile time proc folding, causing issues when code is generated for the instantiated routine. Now, instantiated generic procs are treated as never being inside a `typeof` context. This is probably an arbitrary special case and more issues with the `typeof` behavior from #22022 are likely. Ideally this behavior would be removed but it's necessary to accomodate the current [proc `declval` in the package `stew`](status-im/nim-stew#190), at least without changes to `compileTime` that would either break other code (making it not eagerly fold by default) or still require a change in stew (adding an option to disable the eager folding). Alternatively we could also make the eager folding opt-in only for generic compileTime procs so that #22022 breaks nothing whatsoever, but a universal solution would be better. Edit: Done in #24230 via experimental switch
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#24229 was merged, this PR is out of date, but this might come up again later |
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fwiw, I think this PR was better - the design of |
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We can probably still address that, it's just a matter of finding a good replacement for it. This PR might have made that more complicated if anything |
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fixes #24228, refs #22022
The
typeofbehavior from #22022 causes issues like #24228, but it's required for the procdeclvalin the packagestewto keep working as expected with the rest of #22022. To accomodate this, the generic compileTime proc behavior in #22022 is now opt-in with the switch--experimental:genericProcCompileTime, so that packages can continue to work until we have a proper design forcompileTime.Another option instead of using an experimental switch would be to add a pragma like
constantFoldthat needs to be added to individual generic procs to enable compileTime folding for them, maybe for all procs eventually (it would break code currently if required for all procs). But this is a language addition.Will add to changelog if accepted. Mutually exclusive with #24229.