Nested structs don't get the completion popup

[andreakarasho]

const TestStr = struct {
    const StrInside = struct {
        a: f32,
        b: f32,
    };

    fn func() void {
        var str = StrInside{
            . // ---> shows nothing. Should display `a` or `b`
        };
    }
};

[Techatrix]

This boils down to the same issue as #1535 just applied to struct inits. This may be fixed by #1536.

[FnControlOption]

This appears to be what's happening:

1. When the parser reaches the ., it doesn't find .foo =, so it assumes we're initializing an array.
2. Thus, it expects an expression but doesn't find one, so it returns an error.
3. Then, the parser calls findNextStmt to try skipping the var str statement. However, it sees the } before the ; and exits early. As a result, the parser thinks the } that closes func is for the TestStr struct.
4. Then, it throws another error when it doesn't find a semicolon after the }. This results in TestStr not being added as a member of the current file's root struct.
5. Then when ZLS iterates over the members of the root struct, it is unable to create a scope for TestStr and add a declaration for StrInside.

If you move StrInside outside of TestStr, then ZLS is able to add StrInside as a declaration in the root struct:

const StrInside = struct {
    a: f32,
    b: f32,
};

const TestStr = struct {
    fn func() void {
        var str = StrInside{
            . // ---> this works
        };
    }
};

One potential way to fix this is to modify the parser to keep track of how many unclosed { it currently has (e.g. by adding an additional field to the Parse struct). Then when it sees a }, it can check whether it closes a { for the current unfinished statement.