match: else required even if all cases are covered

[PottierLoic]

Describe the bug

In the following code, the match is covering all cases but compiling still trigger an error saying an else is required.

Reproduction Steps

fn perlin_grad_2d(hash int, x f64, y f64) f64 {
	return match hash & 0xF {
		0x0 { x + y }
		0x1 { -x + y }
		0x2 { x - y }
		0x3 { -x - y }
		0x4 { x }
		0x5 { -x }
		0x6 { x }
		0x7 { -x }
		0x8 { y }
		0x9 { -y }
		0xA { y }
		0xB { -y }
		0xC { y + x }
		0xD { -y }
		0xE { y - x }
		0xF { -y }
	}
}

fn main() {
	nb := perlin_grad_2d(5, 2.3, 5.4)
	println(nb)
}

Expected Behavior

The code should instead compile correctly.

Current Behavior

It trigger this error :

C:\Users\loicp\Documents\GitHub\vsl>v run test.v
test.v:2:9: error: match must be exhaustive (add `else {}` at the end)
    1 | fn perlin_grad_2d(hash int, x f64, y f64) f64 {
    2 |     return match hash & 0xF {
      |            ~~~~~~~~~~~~~~~~~~
    3 |         0x0 { x + y }
    4 |         0x1 { -x + y }

Possible Solution

I think compiler check the type of hash instead of hash & 0xF to determine if all cases are covered.

Additional Information/Context

No response

V version

V 0.4.10 86536e4

Environment details (OS name and version, etc.)

V full version	V 0.4.10 dd083e7687d0e4aafd99bdf9f34011757d6e0628.86536e4
OS	windows, Microsoft Windows 11 Professionnel 26100 64-bit
Processor	16 cpus, 64bit, little endian, 11th Gen Intel(R) Core(TM) i9-11900K @ 3.50GHz
Memory	18.95GB/31.83GB
V executable	C:\Users\loicp\Documents\GitHub\v\v.exe
V last modified time	2025-03-31 22:15:36
V home dir	OK, value: C:\Users\loicp\Documents\GitHub\v
VMODULES	OK, value: C:\Users\loicp.vmodules
VTMP	OK, value: C:\Users\loicp\AppData\Local\Temp\v_0
Current working dir	OK, value: C:\Users\loicp\Documents\GitHub\vsl
Git version	git version 2.44.0.windows.1
V git status	weekly.2025.03-437-g86536e45
.git/config present	true
cc version	N/A
gcc version	gcc (GCC) 11.2.0
clang version	N/A
msvc version	N/A
tcc version	tcc version 0.9.27 (x86_64 Windows)
tcc git status	thirdparty-windows-amd64 b425ac82
emcc version	N/A
glibc version	N/A

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[huly-for-github[bot]]

Connected to Huly®: V_0.6-22490

[jorgeluismireles]

Here V is requesting an else branch that will have dead code. I think is difficult for the compiler to consider all potential cases to prevent dead code. Recalls me this issue.

[jorgeluismireles]

Next function match covers all u8 cases

fn func(u u8) {
	match u {
		0...254 {
			println('low')
		}
		255 {
			println('hi')
		}
	}
}

even though the compiler says:

code.v:2:2: error: match must be exhaustive (add `else {}` at the end)
    1 | fn func(u u8) {
    2 |     match u {
      |     ~~~~~~~~~
    3 |         0...254 {
    4 |             println('low')

[changrui]

我觉得应该要else{}, 方便以后修改代码。

[Avey777]

我觉得应该要else{}, 方便以后修改代码。

I agree