Pipeline depth is not checked when pipeline result is returned

use lib::sprites;
use lib::tiles;

pipeline(0) color(vga_clk: clk, offset: int<10>, pixel_x: int<15>, pixel_y: int<15>) -> (int<8>, int<8>, int<8>) {
    let tile_dx: int<6> = trunc(trunc(pixel_x) + offset);
    let tile_dy: int<6> = trunc(pixel_y);
    inst(1) sprites::sprite_rom(vga_clk, tiles::Tile::Snow(), tile_dx, tile_dy)
}