Don't allow `self` param for implicit method declarations. fixes #71 #430

Job	Run time
docs	56s
host=ubuntu-22.04 cmd=cli target=x86_64-linux-gnu mode=release	2m 27s
host=ubuntu-22.04 cmd=cli target=x86_64-selinux-gnu mode=release	2m 12s
host=macos-12 cmd=cli target=x86_64-macos-none mode=release	2m 14s
host=macos-12 cmd=cli target=aarch64-macos-none mode=release	2m 21s
host=windows-2022 cmd=cli target=x86_64-windows-gnu mode=release	2m 25s
host=windows-2022 cmd=lib target=x86_64-windows-gnu mode=release	1m 49s
host=ubuntu-22.04 cmd=web-lib target=wasm32-freestanding mode=release	40s
host=ubuntu-22.04 cmd=cli target=wasm32-wasi mode=release	45s
host=ubuntu-22.04 cmd=lib target=x86_64-linux-gnu mode=release	1m 24s
host=macos-12 cmd=lib target=x86_64-macos-none mode=release	1m 33s
host=macos-12 cmd=lib target=aarch64-macos-none mode=release	55s
Release	1s
	19m 42s

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