Sum types of Fn and Optional Fn Types makes unknown function

[shininglove]

V doctor:

V full version: V 0.4.7 63957f2.b79aa02
OS: linux, Linux version 5.15.153.1-microsoft-standard-WSL2 (root@941d701f84f1) (gcc (GCC) 11.2.0, GNU ld (GNU Binutils) 2.37) #1 SMP Fri Mar 29 23:14:13 UTC 2024 (WSL 2)
Processor: 16 cpus, 64bit, little endian, Intel(R) Core(TM) i7-10700F CPU @ 2.90GHz

getwd: /home/shininglove/langs/v/bug_report
vexe: /home/shininglove/programs/v/v
vexe mtime: 2024-09-23 02:09:08

vroot: OK, value: /home/shininglove/programs/v
VMODULES: OK, value: /home/shininglove/.vmodules
VTMP: OK, value: /tmp/v_1000

Git version: git version 2.46.1
Git vroot status: weekly.2024.37-51-gb79aa020
.git/config present: true

CC version: cc (GCC) 14.2.1 20240910
thirdparty/tcc status: thirdparty-linux-amd64 0134e9b9

What did you do?
./v -g -o vdbg cmd/v && ./vdbg src/main.v

module main

type DataFn = fn (name string) string

type DataFnOptional = fn (name string) ?string

type Data = DataFn | DataFnOptional

fn which_lang(name string) string {
	return name
}

fn which_lang_maybe(name string) ?string {
	return name
}

fn find_func(name string) ?Data {
	return match name {
		'vlang' { which_lang }
		'blang' { which_lang_maybe }
		else { none }
	}
}

fn main() {
	func := find_func('vlang')?
	option := func('options')
	println(option)
}

What did you expect to see?

a print of 'options'

What did you see instead?

src/main.v:27:2: warning: unused variable: `option`
   25 | fn main() {
   26 |     func := find_func('vlang')?
   27 |     option := func('options')
      |     ~~~~~~
   28 |     println(func)
   29 | }
src/main.v:27:12: error: unknown function: func
   25 | fn main() {
   26 |     func := find_func('vlang')?
   27 |     option := func('options')
      |               ~~~~~~~~~~~~~~~
   28 |     println(func)
   29 | }
src/main.v:27:9: error: assignment mismatch: 1 variable but `func()` returns 0 values
   25 | fn main() {
   26 |     func := find_func('vlang')?
   27 |     option := func('options')
      |            ~~
   28 |     println(func)
   29 | }
If the code of your project is in multiple files, try with `v src` instead of `v src/main.v`

Note

You can use the 👍 reaction to increase the issue's priority for developers.

Please note that only the 👍 reaction to the issue itself counts as a vote.
Other reactions and those to comments will not be taken into account.

[yuyi98]

The usage is wrong.

type DataFn = fn (name string) string

type DataFnOptional = fn (name string) ?string

type Data = DataFn | DataFnOptional

fn which_lang(name string) string {
	return name
}

fn which_lang_maybe(name string) ?string {
	return name
}

fn find_func(name string) ?Data {
	return match name {
		'vlang' { which_lang }
		'blang' { which_lang_maybe }
		else { none }
	}
}

fn main() {
	func := find_func('vlang')?
	if func is DataFn {
		option := func('options')
		println(option)
	} else if func is DataFnOptional {
		option := func('options')?
		println(option)
	}
	println(func)
}

PS D:\Test\v\tt1> v run .
options
Data(fn (string) string)

[shininglove]

oh! thanks! I'll use this

Do you think there should be some kind of warning from the compiler to use this way?

[shininglove]

The usage is wrong.

type DataFn = fn (name string) string

type DataFnOptional = fn (name string) ?string

type Data = DataFn | DataFnOptional

fn which_lang(name string) string {
	return name
}

fn which_lang_maybe(name string) ?string {
	return name
}

fn find_func(name string) ?Data {
	return match name {
		'vlang' { which_lang }
		'blang' { which_lang_maybe }
		else { none }
	}
}

fn main() {
	func := find_func('vlang')?
	if func is DataFn {
		option := func('options')
		println(option)
	} else if func is DataFnOptional {
		option := func('options')?
		println(option)
	}
	println(func)
}

PS D:\Test\v\tt1> v run .
options
Data(fn (string) string)

It seems like using this is only okay if you're not going to use the variable ('option' in this case) outside the if statements, but this breaks if you need to use it outside of it (which is what I need to do)

[felipensp]

Not a bug. Thanks.

[shininglove]

Thanks I was looking for this:

fn main() {
	func := find_func('vlang')?
	option := match func {
		DataFn { func() }
                DataFnOptional{ func()? }
	} 
	println(option)
}

in case someone has this same problem