Fixes shadow_same's false positive for #7915

[surechen]

Fix shadow_same's false positive for async function's params(Fixes #7915):

Example Code:

#![deny(clippy::shadow_same)]

pub async fn foo(_a: i32) {
}

Output:

error: `_a` is shadowed by itself in `_a

Hir:

pub async fn foo(_a: i32)
 ->
     /*impl Trait*/ #[lang = "from_generator"](move |mut _task_context|
                                                   {
                                                       let _a = _a;
                                                       { let _t = { }; _t }
                                                   })

Skip checking async function's params.

changelog: Fix shadow_same's false positive for async function's params

[rust-highfive]

r? @giraffate

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[giraffate]

It might be simpler to check DesugaringKind. This may help us:
#7174.

[surechen]

It might be simpler to check DesugaringKind. This may help us: #7174.
Thank you very much. By checking [DesugaringKind] is more concise and more accurate than my method.

[giraffate]

@bors r+

It looks good, thanks!

[bors]

📌 Commit 846c0be has been approved by giraffate

[bors]

⌛ Testing commit 846c0be with merge de2208a...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: giraffate
Pushing de2208a to master...