Add try_newtype_datatype! for fallible domain conversions#21
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`newtype_datatype!` handles infallible `Owned -> Newtype` conversions.
`try_newtype_datatype!` is its fallible sibling, for newtypes that
`impl TryFrom<Owned>` (the build direction, `From<Newtype> for Owned`,
stays infallible).
Consistent with `Column`'s "validate once at construction, then read
infallibly" contract, every value is checked eagerly in `downcast`
(`Column::try_new` and derive parsing). A rejected value stops there,
boxing the `TryFrom` error into the new `ColumnError::Conversion`,
surfaced as the new `ErrorKind::Conversion { column, source }` once the
column name is known.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
These are all TryFrom a primitive quiver already supports (infallible back), so they slot straight into try_newtype_datatype!: - NonZeroI8..I64, NonZeroU8..U64, stored as their plain integer - char, stored as UInt32 (surrogates/out-of-range rejected) Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
newtype_datatype!handles infallibleOwned -> Newtypeconversions. This addstry_newtype_datatype!, its fallible sibling, for newtypes thatimpl TryFrom<Owned>— the build direction (From<Newtype> for Owned) stays infallible. TheTryFrom::Errormust bestd::error::Error + Send + Sync + 'static.Consistent with
Column's "validate once at construction, then read infallibly" contract, every value is checked eagerly indowncast(Column::try_newand the derive's record-batch parsing). A rejected value stops there, boxing theTryFromerror into the newColumnError::Conversion, surfaced as the newErrorKind::Conversion { column, source }once the column name is known. After construction, element access stays infallible.Same
noref/primitivearm options asnewtype_datatype!.Testing
fallible_newtype_columnsintegration test (Even/NotEvennewtype): build via infallibleFrom, borrowed + owned reads,primitivebulkas_slice, eager rejection attry_new→ColumnError::Conversion,Option<Even>null-skipping, andErrorKind::Conversionviafrom_record_batch_and_name.cargo clippy --all-features --all-targetsclean;cargo test --all-featuresgreen.Compatibility
Additive: new macro plus new non-exhaustive-style variants on
ColumnErrorandErrorKind. Both enums already carried multiple variants; downstream exhaustivematches on them would need the new arm.🤖 Generated with Claude Code