Not memory safety.

> Zig is also good at game development which Rust is not good at.

Let's see. Over just the past year in Bevy I've implemented GPU driven rendering, two-phase GPU occlusion culling, specular tints and maps, clustered decals, multi-draw, bindless textures, mixed lighting, bindless lightmaps, glXF support, skinned mesh batching, light probe clustering, visibility ranges with dithering, percentage-closer soft shadows, additive animation blending, generalized animation, animation masks, offset allocation, volumetric fog, the postprocessing infrastructure, chromatic aberration, SMAA, PBR anisotropy, skinned motion vectors, screen-space reflections, depth of field, clearcoat, filmic color grading, GPU frustum culling, alpha-to-coverage, percentage-closer filtering, animation graphs, and irradiance volumes. In addition to extremely rapid general engine progress, there have also successful titles, such as Tiny Glade.

Whether Rust can be a productive language for game development was an interesting question a few years ago. At this point the answer is fairly clear.

While I wish this were true, I very much doubt it, at least not until Zig has proper interfaces and gives up its weird hangup on anonymous functions. It's also extremely easy to effectively lose access to Zig features without cluttering your code. For example, say you want to use libevent in Zig: your event callbacks must use C calling conventions, meaning you lose access to try and errdefer, which are two of the most defining features of Zig. And while you can remedy this by having the callback invoke a Zig function, doing that just doubles every interaction between your Zig code and libevent, which is already cluttered because of the lack of anonymous functions.

These things aren't as important as compile times, but they are annoyances that will drive a non-zero amount of people away.