Syn dependency when trying to use maturin on a Mac

Question

I am trying to follow the quickstart of maturin. However, after creating a project and copying the Cargo.toml over I always get this issue when I run cargo build.

> cargo build
warning: unused manifest key: build-system
warning: unused manifest key: tool
    Updating crates.io index
error: failed to select a version for the requirement `syn = "^2.0.59"`
candidate versions found which didn't match: 2.0.56, 2.0.55, 2.0.54, ...
location searched: crates.io index
required by package `pyo3-macros-backend v0.23.1`
    ... which is depended on by `pyo3-macros v0.23.1`
    ... which is depended on by `pyo3 v0.23.1`
    ... which is depended on by `guessing-game v0.1.0 (/Users/vincent/Development/guessing-game)`

I tried installing rust (I had a version locally that was multiple years old at this point) but it did not help. Google also did not return anything useful. Anybody know

Answer 1

It turned out that I was using a version of Rust that was simply too old. Moving my code to Github codespaces immediately fixed everything and so did upgrading my local setup.