opensym as node kind + fixed experimental switch

[metagn]

refs #23873 (comment), fixes #23386, fixes #23385, supersedes #23572

Turns the nfOpenSym node flag implemented in #23091 and extended in #23102 and #23873, into a node kind nkOpenSym that forms a unary node containing either nkSym or nkOpenSymChoice. Since this affects macros working on generic proc AST, the node kind is now only generated when the experimental switch genericsOpenSym is enabled, and a new node flag nfDisabledOpenSym is set to the nkSym or nkOpenSymChoice when the switch is not enabled so that we can give a warning.

Now that the experimental switch has more reasonable semantics, we define nimHasGenericsOpenSym2.

[metagn]

Seems to work, but until packages can handle it (macros just need simple skips AFAIK) or until regressions not detected in CI are fixed the node probably shouldn't be generated without the experimental switch enabled. So for the warning we probably need something like #23572, swapping out the existing node flag with one that only exists for a warning and is temporary. I'll do it in this PR if there are no objections, the other PR is out of date already.

[Araq]

swapping out the existing node flag with one that only exists for a warning and is temporary. I'll do it in this PR if there are no objections, the other PR is out of date already.

Fine with me.

[Araq]

Please rebase.

[metagn]

Done

[arnetheduck]

shouldn't this be defined only when the experimental is on?

[metagn]

The nimHas defines usually signal that the experimental switch is available, checking if it's enabled is trickier since it can change depending on the context with push experimental etc. #23933 was opened recently related to this

[arnetheduck]

turns out nimHasGenericsOpenSym is already declared, but for the broken version shipped in 2.0.8:

• https://github.com/nim-lang/Nim/blob/v2.0.8/compiler/condsyms.nim#L103
• https://github.com/nim-lang/Nim/blob/v2.0.8/compiler/options.nim#L224

will need a new name for this new, working version 🎉

[arnetheduck]

nimHasGenericsOpenSym2?

[metagn]

Changed to nimHasGenericsOpenSym2

[arnetheduck]

not sure it's intended, but compiling this branch (3fe15eb) results in lots of warnings:

....
/home/arnetheduck/src/Nim/compiler/ic/cbackend.nim(106, 31) template/generic instantiation of `==` from here
/home/arnetheduck/src/Nim/lib/system/comparisons.nim(324, 16) Warning: a new symbol 'true' has been injected during instantiation of ==, however 'true' [enumField declared in /home/arnetheduck/src/Nim/lib/system/basic_types.nim(46, 16)] captured at the proc declaration will be used instead; either enable --experimental:genericsOpenSym to use the injected symbol or `bind` this captured symbol explicitly [GenericsIgnoredInjection]
.
/home/arnetheduck/src/Nim/compiler/ic/integrity.nim(46, 24) template/generic instantiation of `containsOrIncl` from here
/home/arnetheduck/src/Nim/lib/pure/collections/setimpl.nim(59, 17) Warning: a new symbol 'defaultInitialSize' has been injected during instantiation of containsOrIncl, however 'defaultInitialSize' [const declared in /home/arnetheduck/src/Nim/lib/pure/collections/sets.nim(89, 3)] captured at the proc declaration will be used instead; either enable --experimental:genericsOpenSym to use the injected symbol or `bind` this captured symbol explicitly [GenericsIgnoredInjection]
/home/arnetheduck/src/Nim/compiler/ic/integrity.nim(46, 24) template/generic instantiation of `containsOrIncl` from here
/home/arnetheduck/src/Nim/lib/pure/collections/setimpl.nim(67, 14) template/generic instantiation of `enlarge` from here
/home/arnetheduck/src/Nim/lib/pure/collections/setimpl.nim(43, 16) template/generic instantiation of `rawInsert` from here
/home/arnetheduck/src/Nim/lib/pure/collections/setimpl.nim(28, 17) Warning: a new symbol 'defaultInitialSize' has been injected during instantiation of rawInsert, however 'defaultInitialSize' [const declared in /home/arnetheduck/src/Nim/lib/pure/collections/sets.nim(89, 3)] captured at the proc declaration will be used instead; either enable --experimental:genericsOpenSym to use the injected symbol or `bind` this captured symbol explicitly [GenericsIgnoredInjection]
.
/home/arnetheduck/src/Nim/compiler/ic/navigator.nim(96, 26) template/generic instantiation of `containsOrIncl` from here
/home/arnetheduck/src/Nim/lib/pure/collections/setimpl.nim(59, 17) Warning: a new symbol 'defaultInitialSize' has been injected during instantiation of containsOrIncl, however 'defaultInitialSize' [const declared in /home/arnetheduck/src/Nim/lib/pure/collections/sets.nim(89, 3)] captured at the proc declaration will be used instead; either enable --experimental:genericsOpenSym to use the injected symbol or `bind` this captured symbol explicitly [GenericsIgnoredInjection]

[arnetheduck]

testing this, the semantics of push experimental are quite weird:

Neither of these two work at top-level - the when condition is basically to allow -d:resultsGenericsOpenSym to enable the experimental feature for results only.

when condition:
  {.experimental: "genericsOpenSym".}
  {.push experimental: "genericsOpenSym".}

However, in a situation analogous to the following, the push covers both a and b, even though the push is only inside a:

template a =
  when condition:
    {.push experimental: "genericsOpenSym".}

template b = 
  template injector = discard # this works now

It's kind of weird that inside a template scope, pushing extends to other unrelated templates but not outside..

[metagn]

not sure it's intended, but compiling this branch (3fe15eb) results in lots of warnings:

Definitely not, my bad, I moved the warnings to the wrong spot in the code

[arnetheduck]

arnetheduck/nim-results#35 updated to work with this branch - also includes an ugly emulation hack for Nim versions that don't have this feature..

[github-actions]

Thanks for your hard work on this PR!
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