Rust relies on a newer version of LLVM than Emscripten is based on (as Emscripten-fastcomp is based on the PNaCl fork of LLVM, which is lagging behind). Once th

Rust relies on a newer version of LLVM than Emscripten is based on (as Emscripten-fastcomp is based on the PNaCl fork of LLVM, which is lagging behind). Once the PNaCl fork is updated and Emscipten rebases, or they rebase onto LLVM proper, then it should be doable fairly easily.