checker: array.insert() does not work if the array contains fixed arrays

[Le0Developer]

V doctor:

V full version: V 0.4.8 602b097.e32e9f7
OS: macos, macOS, 15.1.1, 24B2091
Processor: 10 cpus, 64bit, little endian, Apple M4

getwd: /Users/leodev/p/v/fast2
vexe: /Users/leodev/p/v/v/v
vexe mtime: 2024-12-07 13:12:52

vroot: OK, value: /Users/leodev/p/v/v
VMODULES: OK, value: /Users/leodev/.vmodules
VTMP: OK, value: /tmp/v_501

Git version: git version 2.47.0
Git vroot status: weekly.2024.49-33-ge32e9f70 (1 commit(s) behind V master)
.git/config present: true

CC version: Apple clang version 16.0.0 (clang-1600.0.26.4)
emcc version: N/A
thirdparty/tcc status: thirdparty-macos-arm64 713692d4

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

fn main() {
	mut arr := [][2]int{}
	arr.insert(0, [1, 2]!)
	println(arr)
}

What did you expect to see?

Successful compilation

What did you see instead?

repro.v:3:16: error: cannot use `[2]int` as `voidptr` in argument 2 to `[][2]int.insert`
    1 | fn main() {
    2 |     mut arr := [][2]int{}
    3 |     arr.insert(0, [1, 2]!)
      |                   ~~~~~~~
    4 |     println(arr)
    5 | }

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_{Huly®: V_0.6-21528}

[felipensp]

The correct would be:

fn main() {
	mut arr := [][2]int{}
	arr.insert(0, [[1, 2]!])
	println(arr)
}

[Le0Developer]

The correct would be:

fn main() {
	mut arr := [][2]int{}
	arr.insert(0, [[1, 2]!])
	println(arr)
}

no? this is insert, not the private insert_many or arr <<, this function takes a single item.

[jorgeluismireles]

I think LeoDeveloper is right. I think the problem could be related to the fixed array. For normal array elements below 7,8 are appended ok.

fn main() {
	mut arr := [][]int{}
	arr << [1, 2]
	arr << [[3, 4], [5, 6]]
	arr.insert(arr.len, [7, 8]) // <- works as expected
	arr.insert(arr.len, [[9,10]]) // <- not rejected but C error
	println(arr)
}

But I was expecting the compiler will reject elements 9 and 10, but not, generates a C error :-(

[JalonSolov]

The last one should have been a V error. You tried to insert an array of arrays as an array in the array.

It would be the same as trying

mut arr := []int{}
arr.insert(arr.len, [9,10])

In other words, the thing being inserted must have one fewer set of [] than what it is being inserted into. That makes this a separate issue from the original, as it has the correct number of sets of [], but it is failing.

[felipensp]

I think we should improve the error message.

bug.v:3:16: error: cannot insert `[]int` to `[][2]int`
    1 | fn main() {
    2 |     mut arr := [][2]int{}
    3 |     arr.insert(0, [1, 2])
      |                   ~~~~~~
    4 |     println(arr)
    5 | }

[JalonSolov]

I agree that the error message could be better, but remember the original code has

arr.insert(0, [1, 2]!)

which should work as it is trying to insert a fixed array, while your example has

arr.insert(0, [1, 2])

which should not, since it isn't a fixed array.