refactor: optimize code based on cargo clippy #1172

Job	Run time
Check io_safety feature (ubuntu-latest)	18s
Checking fmt and docs	29s
Build with no-std	13s
Build and test (ubuntu-latest, nightly)	19s
Check io_safety feature (windows-latest)	1m 23s
Build and test (ubuntu-latest, beta)	18s
Build and test (ubuntu-latest, stable)	20s
Check tokio02 feature	24s
Build and test (windows-latest, nightly)	17s
Check wasm targets (nightly)	23s
Build and test (windows-latest, beta)	18s
Cross compile (i686-unknown-linux-gnu)	1m 8s
Check wasm targets (beta)	24s
Build and test (windows-latest, stable)	19s
Cross compile (powerpc-unknown-linux-gnu)	1m 8s
Check wasm targets (stable)	18s
Build and test (macOS-latest, nightly)	21s
Cross compile (powerpc64-unknown-linux-gnu)	1m 18s
Cross compile (arm-linux-androideabi)	1m 23s
Build and test (macOS-latest, beta)	24s
Build and test (macOS-latest, stable)	17s
	11m 42s

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