hermes

Hermes is an experimental framework for building compilers in Go. It's inspired by the Nanopass Framework and attribute grammars, particularly UUAGC.

Current status

Currently, it's still very early development. Current artifacts:

• example/lang.go

This source file defines all of the sublanguages used through the scheme-to-c example nanopass compiler. It's written in Go-compatible syntax, but the Go semantics are meaningless.

• cmd/mklang

This command, when run within the example subdirectory, transforms lang.go into the lang/L* packages. One package per sublanguage.

• passes/*.go

These source files contain the first several passes of the scheme-to-c compiler, translated into how I envision writing them in Hermes. These are not actual Go source, but again Go-compatible syntax.

• cmd/passify

This command, when run within the example subdirectory, will eventually turn the passes/*.go files into actual executable Go code.

Future direction

The current Hermes prototype was a time-bounded experiment at porting scheme-to-c to work out concrete details and discover implementation hurdles. I don't plan to work on it further in the immediate future, but I hope to revisit eventually.

Some immediate reflections:

Writing the language definitions and passes in Go syntax is convenient because it benefits from existing Go support in IDEs. E.g., I anticipate eventually that referencing standard Go types and functions will be useful, and by writing directly in Go syntax allows code navigation features to work. Certainly writing passes is made somewhat easier because of editor support for referring to the generated structs/interfaces for languages.

However, I'm not fully convinced yet that it's better than defining a custom syntax, as tools like yacc have traditionally done. For example, the https://github.com/a-h/templ project adds JSX-like syntax to Go and introduces new ".templ" files to delineate this change in syntax/semantics, and yet it still advertises good editor support by proxing gopls.