Pain in C++

• tools and compiler/platform differences
• ergonomics and (thread) safety
• community

Why Rust?

• fun & cool: better for a hobby project. It is a need.
• Great tooling
• Options are easier to use than C++'s pointers
• use system over #include
• simpler dependency management
• killer feature is Send and Sync, statically enforcing rules around threading.

Ship of Theseus strategy for the rewrite: component by component. The fish app should work exactly the same.

So if you are trying to draw any conclusions from this, consider the context: A group of people working on a thing in their free time, diverting some effort to work on something else, and deciding that after the work is finished it actually isn’t.

Gripes with Rust

• portability between OS: it allows to miss systems and ignoring version differences
• string translation and localization: format! are checked at compile-time
• building to other targets: "it is often better to use if cfg!(...) instead of #[cfg(...)] because code behind the latter is eliminated very early, so it may be entirely wrong and only shows up when building on the affected system.

They also report mistakes they made.

There are good with quick-wins of the port to Rust. There is also some sad ones: CMake is not removed yet. Cargo is missing some features to install third dependencies (.fish scripts, 130 pages of documentation, the web-config tool and the man page generator).
Cygwin is not a supported platform.