Struct init fields completion.

[llogick]

Up for logic review and a fuzz (suggestions still welcome).

Caveat:

// has to be at root level, ie outside of fns
const MyStruct = path.to.my.MyStruct;
var a = MyStruct{. // now resolved

Note:
Nested structs completion, ie MyStruct{.fld = a, SomeOther{.dlf = 1}, .<complete here>}, is out of scope, use locals.

[leecannon]

This works well for the simple case but there are some very common cases that it does not support:

• types returned by functions (any generic)

fn NonGenericGeneric() type {
    return struct {
        a: bool,
        b: bool,
    };
}

fn nonGenericGeneric() void {
    var r = NonGenericGeneric(){}; // no completion
}

• completion within the container itself

const MyStruct = struct {
    a: bool,
    b: bool,
    
    fn inside() void {
        var s = MyStruct{}; // no completion 
    }
};

fn outside() void {
    var s = MyStruct{}; // completion
}

• file level structs

// inside "MyStruct.zig"
a: bool,
b: bool,

// inside "main.zig"
const MyStruct = @import("MyStruct.zig");

fn topLevelStruct() void {
    var s = MyStruct{}; // no completion 
}

• aliases

const MyStruct = struct {
    a: bool,
    b: bool,
};

const Alias = MyStruct;

fn alias() void {
    var s = Alias{}; // no completion
}

[leecannon]

I'm okay merging this as is, as it does increases ZLS capabilities.
I'm just making note of things that can still be improved in this area.

@nullptrdevs any chance you can rebase?

[llogick]

Thank you for taking the time to review, I will look into all of these, but some initial thoughts:

Case 1: No idea where to start. Something something ComptimeInterpreter.
Case 2: The parser skips creating a node for MyStruct,

const MyStruct = struct {
    a: bool,
    b: bool,
    
    fn inside() void {
        var s = MyStruct{.}; // no completion 
    }
};

fn outside() void {
    var s = MyStruct{}; // completion
    MyStruct. // no completion here either
}

(Custom parser when?) Custom parse tokens looking for same .identifier, MyStruct, then parse .identifiers that might be fields(look for a .colon).
Case 3: This would be priority No.1.
Case 4: How common is this (worth the cpu cycles 😀 )?

[Vaxeral]

There is a bug, struct member completions fail to appear if the struct is defined after it is used.

[Vaxeral]

I am curious to know why this happens.
On the bright site the lsp does show the structure definition when i hover over it. That is good enough for me. :D