nullable type compiler error

[emekoi]

given the following code:

pub const Node = struct {
    children: []?Node,
    data: ?u8,

    fn new() Node {
        return Node {
            .children = undefined,
            .data = null,
        };
    }
};

trying to call Node.new() trips this assertion instead of providing a meaningful error message about how the type is recursive.

[emekoi]

wait, isn't a slice basically a pointer with a length? so why is this type recursion?

[andrewrk]

I don't know where you're getting the idea that this is type recursion, but if you're tripping an assertion then it's a compiler bug.

[tgschultz]

The type is recursive. children is an array of Optional Nodes, each of which contains a children member that is an array of Optional Nodes, each of which contains an array of Optional Nodes, each of which...

You probably either meant children: [alphabet]?*Node (an array of Optional pointers to Node) or children: []?Node (a slice of Optional Nodes).

Also, in the code shown Self is never defined. Not sure if relevant, but if it is it might be related to #1483.

[emekoi]

even when i change children to children: []?Node i still get a compiler error. children: []?*Node works though.

[andrewrk]

That sounds like #1500

[suirad]

Unless this was cut from other code, .data also doesn't have a type.

[emekoi]

so should i close this then?

[andrewrk]

so should i close this then?

No, because it's a compiler bug.

pub const Node = struct {
    children: []?Node,
    data: ?u8,

    fn new() Node {
        return Node{
            .children = undefined,
            .data = null,
        };
    }
};

test "aoeu" {
    _ = Node.new();
}

zig: /home/andy/downloads/zig/src/analyze.cpp:2694: Error resolve_struct_alignment(CodeGen*, ZigType*): Assertion `field->type_entry != nullptr' failed.

[andrewrk]

Proposal to fix this: #2174