Environment details

• Programming language: Rust
• OS: MacOS 15.6.1
• Language runtime version: Rust stable (v1.91.1)
• Package version: google-cloud-auth v1.1.1

Steps to reproduce

rustc --version # rustc 1.91.1 (ed61e7d7e 2025-11-07) which is latest stable rust
 
cargo new foo
cd foo
cargo add google-cloud-auth@=1.1.1
cargo check 

You can see the warning produced by cargo check below.

warning: the following packages contain code that will be rejected by a future version of Rust: num-bigint-dig v0.8.5
note: to see what the problems were, use the option `--future-incompat-report`, or run `cargo report future-incompatibilities --id 1`

To resolve the warning, install the package at 1.1.0 instead.

# still inside foo
cargo add google-cloud-auth@=1.1.0
cargo check

You will see the warning is gone.

It seems this issue was introduced because 1.1.1 relies on jsonwebtoken, which relies on rsa, which relies on v0.8.5 of num-bigint-dig, where this warning originates.

Thanks!