feat: add initial code

[ccoVeille]

the test coverage is limited for now

I will need to consider to generate the tests.

Using generics in the code has huge consequences on unit tests

[ccoVeille]

@ldemailly could you please review ?

[ldemailly]

1.23.1 is out

(and personally I would put just 1.23 so you don't have to keep changing it)

[ldemailly]

or more importantly... you don't want to force users to use 1.23, I wouldn't yet for anything prod

[ccoVeille]

That's right, 1.22 is enough

I simply ran go mod init that set it up like this

Apparently, I'm still go 1.23.0 locally

[ccoVeille]

Fixed in 328cfff

[ldemailly]

I think I have a much simpler implementation

package safecast

import (
	"errors"
)

type Integer interface {
	~int | ~uint | ~int8 | ~uint8 | ~int16 | ~uint16 | ~int32 | ~uint32 | ~int64 | ~uint64
}

var ErrOutOfRange = errors.New("out of range")

func Convert[Tout Integer, Tin Integer](orig Tin) (converted Tout, err error) {
	converted = Tout(orig)
	if Tin(converted) != orig {
		err = ErrOutOfRange
	}
	return
}

done, for all types!

[ldemailly]

sample test/demo:

func TestConvert(t *testing.T) {
	var inp uint32 = 42
	out, err := safecast.Convert[int8](inp)
	t.Logf("Out is %T: %v", out, out)
	if err != nil {
		t.Errorf("unexpected error: %v", err)
	}
	if out != 42 {
		t.Errorf("unexpected value: %v", out)
	}
	inp = 129
	_, err = safecast.Convert[int8](inp)
	t.Logf("Got err: %v", err)
	if err == nil {
		t.Errorf("expected error")
	}
}

outputs

$ go test -v .
=== RUN   TestConvert
    safecast_test.go:12: Out is int8: 42
    safecast_test.go:21: Got err: out of range
--- PASS: TestConvert (0.00s)
PASS

[ccoVeille]

unfortunately your implementation is not safe about the modulo that int conversion implies

int8(0) == int8(-256) == int8(256) == int8(512) ...

https://go.dev/play/p/0g3MBAC36we

I will iterate. Thanks for your inspiring example

[ccoVeille]

Closed in favor of #9

[ccoVeille]

package safecast

import (
	"errors"
)

type Integer interface {
	~int | ~uint | ~int8 | ~uint8 | ~int16 | ~uint16 | ~int32 | ~uint32 | ~int64 | ~uint64
}

var ErrOutOfRange = errors.New("out of range")

func Convert[Tout Integer, Tin Integer](orig Tin) (converted Tout, err error) {
	converted = Tout(orig)
	if Tin(converted) != orig {
		err = ErrOutOfRange
	}
	return
}

done, for all types!

Unfortunately this implementation has some caveats

https://go.dev/play/p/irxvorEcy65

[ldemailly]

In case someone does archeology here, thanks for finding that bug, the fixed version is
https://github.com/ldemailly/go-scratch/blob/main/safecast/safecast.go

(added the 2 tests too)