v
v copied to clipboard
vlang
type alias for 2D array generates compile time error
Describe the bug
This does not compile:
module main
pub type Labels = [][]int
pub fn new_labels(width int, height int) Labels {
//mut labels := [][]int{len: height, init: []int{len: width}} // compiles OK
mut labels := Labels{len: height, init: []int{len: width}} // does not compile
return labels
}
fn main() {
mut labels := new_labels(2,2)
}
Reproduction Steps
Try to compile the above code.
Expected Behavior
I would expect it to compile with no error.
Current Behavior
Get compiler error:
issues/complier_error.v:6:16: error: alias type name: [][]int is not struct type
4 |
5 | pub fn new_labels(width int, height int) Labels {
6 | mut labels := Labels{len: height, init: []int{len: width}}
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7 | return labels
8 | }
Possible Solution
Either fix or update documentation to say its not allowed.
Additional Information/Context
No response
V version
V 0.4.4 ac2dcc2
Environment details (OS name and version, etc.)
EndeavourOS
[!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.
@pd-giz-dave because you assign at the labels var in your function a struct that does not exist ( struct assignation declaration in your example ) and you trying to return it. Moreover, return type of your function is not a struct.
It's not a bug.
The type alias documentation is this: "Type aliases To define a new type NewType as an alias for ExistingType, do type NewType = ExistingType. This is a special case of a sum type declaration." So is "[][]int" not a type? I'm a newbie to V so I niaively interpreted a type alias like a C #define, ie. anywhere where ExistingType is valid so would NewType be. My understanding is clearly wrong, but a fuller explanation in the docs would help.
If we change array to map on Labels, we'll get:
bug.v:7:16: error: direct map alias init is not possible, use Labels(map[int]string{}) instead
So, if we want to support array init via this struct way, probably we should support map too for consistency.
