How to type hint GenericReader?

[quick elbow]

I need to read a complicated binary file that contains data to be parsed into multiple structs:

fn readComplicatedOne(reader: anytype) ComplicatedStruct {
    reader.read(); //...
    return .{...};
}

fn readComplicatedTwo(reader: anytype) ComplicatedStruct2 {
    reader.read(); //...
    return .{...};
}

test "read file" {
    const file = try std.fs.cwd().openFile("my_file.bin", .{ .mode = std.fs.File.OpenMode.read_only });
    const p1 = read()
    var reader = file.reader();
    readComplicatedOne(&reader);
    readComplicatedTwo(&reader);
}

this works, but while writing the "readComplicated" functions, I dont have any help from the language server. I know that reader is some kind of GenericReader(A, B), but I dont know how to write that in the readComplicated* function definitions.

Is there a way to write the read functions signatures in a way I get code completions (functions, signatures, return types) for the reader: GenericReader parameter?

[bold rivet]

firstly, you shouldn't pass a pointer to reader, just pass the reader itself

secondly, zls will try to pick up the type from usages in the same file, so the test should be enough

but it's not always perfect

unfortunately there's not much you can do about that

[quick elbow]

i see. i think I saw a zls config to..build on save? Maybe I can use that and it'll seamlessly work
i gotta say though, I'm not loving this anytype/unconstrained generics business. I know the compiler will eventually scream at me if I pass parameters that doesnt meet the required interface, but being able to declare it would be really awesome