Vala is not a C# subset (though it does significantly resemble C#) and really isn't intended or suitable for writing high-performance code or reusable low-level

Vala is not a C# subset (though it does significantly resemble C#) and really isn't intended or suitable for writing high-performance code or reusable low-level libraries like C or C++ are; it's a way to write GObject-style C without as much boilerplate as it takes in C. For that niche it's quite nice, and helps avoid refcounting errors which can be very subtle in C, but Vala is still a fairly leaky abstraction over the C to which it compiles.