Trying to avoid writing too many returns in if/else or match.

[jorgeluismireles]

The combination of objects with options and created within a function with a single return outside cases if/else or match causes problems. The program:

struct Number {
	natural ?string
	integer string
}

fn number(n int) Number {
	return if n >= 0 { // a single return here
		Number{ natural:'${n}', integer:'${n}' }
	} else {
		Number{ integer:'${n}' }
	}
}

fn main() {
	for n in [1,0,-1] {
		println('${number(n)}')
	}
}

https://play.vlang.io/p/78094800a4

The problem:

Running code...
Can't run code. The server returned an error:
/tmp/v_60000/../../../../../../box/code.v:7: error: ')' expected (got "_t2")
builder error: 
==================
C error found. It should never happen, when compiling pure V code.
This is a V compiler bug, please report it using `v bug file.v`,
or goto https://github.com/vlang/v/issues/new/choose .
You can also use #help on Discord: https://discord.gg/vlang .
Exited with error status 1
Please try again.

A workaround is to use a return for each case (apart changing the ?string by string):

fn number(n int) Number {
	if n >= 0 {
		return Number{ natural:'${n}', integer:'${n}' } // a return here
	} else {
		return Number{ integer:'${n}' } // another return here
	}
}

The expected output:

Number{
    natural: Option('1')
    integer: '1'
}
Number{
    natural: Option('0')
    integer: '0'
}
Number{
    natural: Option(none)
    integer: '-1'
}

I have found this problem more than once trying to avoid writing "too many" returns in functions with a returning match with too many cases and the when the returned object is not trivial.

But now I wonder if is worth to solve the issue mentioned above for this particular case and then later more complex objects could cause new problems, or just encourage to program "the easy way" as in the workaround.

Thoughts?

[felipensp]

PR added to fix this issue #22578

[jorgeluismireles]

Great! Now https://play.vlang.io/p/78094800a4 works and match (which failed as if did) now works also:

fn number(n int) Number {
	return match true {
		n >= 0 {
			Number{ natural:'${n}', integer:'${n}' }
		} else {
			Number{ integer:'${n}' }
		}
	}
}

[Delta456]

I will close this discussion. Thanks @felipensp