First day seems very LLM heavy, and sounds quite odd for Phobos 3. I would like to see Phobos 3 be more betterC forward, since I have found D to be nicer than C for WASM, but you can't use most nice things. Having a default RAII vector class for betterC and a hashmap would be super nice too.
Edit: Also would be nice to adopt move and copy semantics even closer to C++ and maybe need less explicit moves, and ideally less mess with calling __xdtor when trying to do RAII
we shipped druntime on emscripten on the opend side almost two years ago, supporting everything but threads and exceptions (i tested on emcc 3.1.69, i heard a later version of emscripten broke, im not sure). see my blog post from release time: https://dpldocs.info/this-week-in-arsd/Blog.Posted_2024_10_2...
there's a contributor working with both upstream and opend adding wasi support as well, and he also got exception support working, we'll probably ship that next month.
so the full d story on wasm is progressing too.