Macro draw_mesh 

macro_rules! draw_mesh {
    ($pass:expr, $meshes:expr, $handle:expr) => { ... };
    ($pass:expr, $meshes:expr, $handle:expr, $instances:expr) => { ... };
}

Looks up $meshes.get($handle) and draws it — sets the vertex/index buffers and calls draw_indexed, defaulting the instance range to 0..1 (pass a fourth argument for instanced draws). Returns from the enclosing function (via or_return!) if the mesh isn’t ready yet.

draw_mesh!(render_pass, meshes, mesh_handle);
draw_mesh!(render_pass, meshes, mesh_handle, 0..enemy_count);