[charrondev]

I’m guessing the cargo binary has a TOML parser in it. As long as cargo itself doesn’t need TOML support to build that should be fine.

[veber-alex]

cargo itself does need TOML support to build because cargo itself is a Rust crate [0].

But it's not a problem because you build a new version of cargo with an older version of cargo that of course can parse TOML.

[0] https://github.com/rust-lang/cargo/blob/master/Cargo.toml