future_not_send unclear about what value is held across an await

Description

Hi, I love rust-clippy, but one lint which bugs me is future_not_send, because it reads

"future is not Send as this value is used across an await"

and (to me) it's unclear to what "this value" refers, or how to fix the problem

Would it be possible to make the future_not_send lint more clear / explanatory about what exactly is the value being held across the await and, if possible, guide async noobs like me to fix the issue so we could make the future in question implement Send properly?

future_not_send

Sorry, I don't have a great repro I can share right now, let me know if that's necessary and I'll try to come up with one

Version

> rustc -Vv
rustc 1.87.0-nightly (f04bbc60f 2025-02-20)
binary: rustc
commit-hash: f04bbc60f8c353ee5ba0677bc583ac4a88b2c180
commit-date: 2025-02-20
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.0

Additional Labels

No response

Start with the future_not_send lint documentation linked in the issue and inspect how its current diagnostic is presented. Create a minimal async example that triggers the lint, then determine what information can explain the value held across the await and how to fix it. Done means the diagnostic is more specific and actionable, with suitable coverage for the revised wording.