Link: Elm has a new compiler written in Rust

Martin from Spottt has written an article about their new Elm compiler written in Rust. The article details the reason for their decision to rewrite the Elm compiler in Rust, basically build times: Elm 0.19.2 made builds much faster for many projects, but not for ours: our application is probably an outlier for the Haskell compiler. I wonder if they have the same issue that we had at Pakk, which I realise now I never blogged about before. Our issue was the use of large record types. The Elm compiler expands these record types and crucially stores that expanded type in the incremental build files .elmi and .elmo. That meant that these files became very large, and it was the parser of these files that was taking a long time in the compilation. That was why even for an incremental build the compiler would still sometimes take a long time. We had a simple script to find large .elmi files: ...

October 5, 2026 ยท Allan Clark