Guile has a generic VM and extensible compiler tower, so a bug for bug port of elisp was proving to be an effective method. Unfortunately, the project did not i

Guile has a generic VM and extensible compiler tower, so a bug for bug port of elisp was proving to be an effective method. Unfortunately, the project did not interest the Emacs devs so there just wasn't the buy-in necessary to work through the finer details and make it happen for real. You can open a Guile REPL today and switch the language from Scheme to Elisp and hack away. What makes the whole thing so appealing is that the Elisp compiler simply lowers the code to Guile's "tree intermediate language" (Tree-IL) and gets a free ride the rest of the way through optimization and bytecode emission. The biggest impact Elisp support had on core Guile was that a new immediate type had to be added to represent 'nil'. Soon it won't even be much of a stretch to compile Elisp to WebAssembly (would be funny!) once that backend is ready for Scheme. Guile is undervalued as a platform for language implementation and Emacs missed out on a cool opportunity.