This should be more resilient to false positives like in #12245 where a string contains `println`.
disallowed_methods
std::env::var
In 11588 we want to avoid reading from environment variables, 11727 did that well. I wonder if we could leverage tools to help with this. Thankfully, clippy has a `disallowed_methods`[1] lint, helping us enforce the rule. [1]: https://rust-lang.github.io/rust-clippy/stable/index.html#disallowed_methods