chore: add specialized returns, optimize parser #495

Job	Run time
Build wasm	1m 47s
Run tests on macOS arm64 (Apple M1)	1m 21s
Run tests on Linux x86 (stable, no default features)	1m 5s
Run tests on Linux x86 (nightly)	57s
Run tests on Linux x86 (stable)	53s
Run tests on Linux armv7	3m 53s
Run tests on Linux arm64	3m 39s
Run tests on Linux x86 (nightly, no default features)	1m 7s
	14m 42s

Provide feedback