Well, I googled the error message to no luck, I read through the documentation, and I must admit the code from the documentation example https://docs.rs/syn/2.0.38/syn/fn.parse_str.html simply does not compile.

OK, I went back to the playground and ran it from there. The promised AST for `foo(42)` looks like, well, `foo (42)` (notice the space.)

The language itself might (or might not) be brilliant, but the toolchain simply sucks.

Error messages are poor, and documentation is too succinct.

Would not recommend.