That sounds great! I'd love to hear more about that. Are you looking to support extension of Tcl with WebAssembly, or using Tcl inside WebAssembly?
I think wasmtime would likely be a good fit for your use case; you could either use the wasmtime C API, or use Rust to bind to Tcl and to the wasmtime-api Rust crate.
I've found it quite easy to embed wasmtime and run a simple WebAssembly module.
This is going to be a Tcl extension named "webassembly" that then allows you to load other Tcl extensions that are compiled to WebAssembly.
Right now Tcl loads binary extensions using the "load" command, this will load a shared object (.so, .dylib, .shlib, .dll, .a, whatever your OS supports for runtime loading) and call <ExtensionName>_Init.
My plan is to create a new command named "webassembly::load" that will open a WebAssembly module and provide ... some way ... to call <ExtensionName>_Init as well as some way for the extension to make calls back the ~200 Tcl API functions and some selected other APIs per platform (Solaris, AIX, FreeBSD, Linux, Windows, macOS, HP-UX, etc).
Additionally, a mechanism (probably in the form of an SDK) for Tcl Extension maintainers to compile their extension targeting being loaded by "webassembly::load" with the APIs mentioned above being available. Most Tcl extensions right now are written in C or C++.
Makes perfect sense. I look forward to seeing your work when it's ready! Please feel free to ask if there's anything we can do to help, or if you run into any areas where the APIs could be easier to use.
I think wasmtime would likely be a good fit for your use case; you could either use the wasmtime C API, or use Rust to bind to Tcl and to the wasmtime-api Rust crate.
I've found it quite easy to embed wasmtime and run a simple WebAssembly module.
See https://github.com/bytecodealliance/wasmtime-demos for some samples of how to do so.