hcrosse opened a new issue, #1502:
URL: https://github.com/apache/arrow-go/issues/1502
### Describe the bug, including details regarding any error messages,
version, and platform.
Casting `bool`, `decimal128` or `decimal256` arrays to `int16` can return
wrong values without an error. Safe decimal casts also reject values that fit
in `int16` but not `int8` with `integer value out of bounds`.
I reproduced this on main at `32947b25` and on v18.8.0 with Go 1.26.10 on
macOS arm64. The incorrect kernel registration is also present in v18.0.0.
**Reproduction**
Save this as `main.go` in a new subdirectory of an arrow-go checkout at
`32947b259414a77ae6347d3d29bd69ec00b9d560`, then run `go run .` from that
directory:
```go
package main
import (
"context"
"fmt"
"strings"
"github.com/apache/arrow-go/v18/arrow"
"github.com/apache/arrow-go/v18/arrow/array"
"github.com/apache/arrow-go/v18/arrow/compute"
"github.com/apache/arrow-go/v18/arrow/memory"
)
func cast(dt arrow.DataType, values string) {
in, _, err := array.FromJSON(memory.DefaultAllocator, dt,
strings.NewReader(values))
if err != nil {
panic(err)
}
defer in.Release()
out, err := compute.CastArray(context.Background(), in,
compute.SafeCastOptions(arrow.PrimitiveTypes.Int16))
if out != nil {
defer out.Release()
}
fmt.Println(out, err)
}
func main() {
cast(arrow.FixedWidthTypes.Boolean, `[true, false, true, true]`)
cast(&arrow.Decimal128Type{Precision: 5, Scale: 0}, `["200", "-300"]`)
}
```
Actual output:
```text
[1 257 0 0] <nil>
<nil> invalid: integer value out of bounds
```
Expected output:
```text
[1 0 1 1] <nil>
[200 -300] <nil>
```
**Cause**
`cast_int16` uses `kernels.GetCastToInteger[int8]`. The boolean and decimal
kernels use that type parameter for writes and decimal bounds checks, so they
write `int8` values into an `int16` buffer and check against the `int8` range.
https://github.com/apache/arrow-go/blob/32947b259414a77ae6347d3d29bd69ec00b9d560/arrow/compute/cast.go#L844
I have a patch with tests and can open a PR.
### Component(s)
Other
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