Add default keyword for generating a default value of any type#2683
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mergify[bot] merged 5 commits intomainfrom Feb 2, 2026
Merged
Add default keyword for generating a default value of any type#2683mergify[bot] merged 5 commits intomainfrom
default keyword for generating a default value of any type#2683mergify[bot] merged 5 commits intomainfrom
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Co-authored-by: Restyled.io <commits@restyled.io>
xsebek
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Feb 2, 2026
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Nice 👍 I was surprised it tried the right branch as well.
| -- (rec l. (Int * l) + Unit). Since we default to generating the left | ||
| -- side of a sum type, this will recurse forever generating inl (0, | ||
| -- inl (0, inl (0, ...))). To support recursive types we would have | ||
| -- to do more sophisticated analysis to find a finite value to pick. |
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Would a set of encountered types (?) in recursion do the trick? 🤔
It seems the only possible problem are loops and we should be able to detect them if types have Ord.
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Oh, good idea. Your comment was just what I needed to see how to make it work. It wasn't all that hard in the end, so I added it. 😄
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Merge Queue Status✅ The pull request has been merged at 31f923b This pull request spent 14 seconds in the queue, including 2 seconds running CI. Required conditions to merge
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defaultmust be applied to a type literal, i.e.default @Intordefault @(Text -> Int)or whatever. It can also be used with type synonyms, as intydef X = [... record type ...] end; default @X. It is replaced with a default value at compile time, sodefaultnever has to be interpreted at run time. Making it generate a default value at run time would be more flexible (it would allow e.g. higher-order uses) but getting access to a relevant context of type synonyms at runtime is tricky, so I figured static compile-timedefaultvalue generation would be simpler.defaultshould support all inhabited types, including recursive types that have finite values.Currently,
defaultrequires no special capability to use, but I could be convinced otherwise.Closes #2192.