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.