Prevent clippy::needless_lifetimes false positive in async function definition

[samueltardieu]

Scan OpaqueDef bounds for lifetimes as well. Those OpaqueDef instances are generated while desugaring an async function definition.

This fixes #7893

changelog: Prevent [clippy::needless_lifetimes] false positive in async function definition

[rust-highfive]

r? @xFrednet

(rust-highfive has picked a reviewer for you, use r? to override)

[xFrednet]

This looks good to me 👍. I'm not quite sure how these OpaqueDef types are used inside rustc, I'll therefore ask some team members to double-check this PR 🙃

[samueltardieu]

I'm not quite sure how these OpaqueDef types are used inside rustc,

According to the documentation of OpaqueDef, this is the type used to expand impl Trait (and async fn gets expanded into a function returning impl Future<_>). The documentation also indicates that the second field of OpaqueDef contains the lifetimes bound on the impl Trait, hence this patch.

[flip1995]

Thanks for the further explanation. This LGTM. There's a small NIT with the test.

[flip1995]

@bors r=xFrednet,flip1995

Thanks!

[bors]

📌 Commit 9bcf966 has been approved by xFrednet,flip1995

[bors]

⌛ Testing commit 9bcf966 with merge 9720619...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: xFrednet,flip1995
Pushing 9720619 to master...