I think the most promising thing on this front is Cranelift (https://github.com/CraneStation/cranelift). The idea is that, when cranelift is ready, we might use it for debug builds (but still use LLVM for release builds).

I'm not sure when the last time you've used Rust is, but that hasn't been true in quite a while (not sure how long exactly). Cargo now has incremental compilation, and it's turned on by default. It's great!

I dabble on Rust regularly, usually during plane or train trips.

It still doesn't do incremental linking, and cargo still builds everything from scratch without any support for binary libraries.

Binary libraries don't help so much -- many libraries use generic types and functions (those are instantiated and compiled for each specific instance) which can only be delivered as library "metadata", not codegen'ed, and the latter is the very slow part.

Wrong since C++11 introduced external templates for common instatiation types.

Additionally, it is not like every C++ library is full of meta-programming templates.

Finally, there are other languages with library "metadata" and generic data types, which can easily beat Rust compile times like Delphi, Eiffel and Ada.

Delphi and Eiffel compilers don't do anywhere near the same level of optimization as LLVM does.

And are you sure GCC's Ada has better compile times? My sense is that so few people use Ada at scale that we don't really know.