Has anyone used Rust to write an interpreter for INTERCAL yet?

Of course. [0]

[0] https://github.com/birkenfeld/rick

Oh good. Though it's a shame that the test suite is a `test.py` file instead of `cargo test`; it would have been extremely satisfying to know that the Rust project would run the test suite for an INTERCAL compiler on a regular basis as part of Crater.

Wash your mouth out with FROMs :)

You didn't say PLEASE.