https://timothygu.me/es-howto/
statements as expressions
https://www.mail-archive.com/es-discuss@mozilla.org/msg11218.html
completion values are unfortunately defined dynamically:
https://www.mail-archive.com/es-discuss@mozilla.org/msg11234.html
mike's consideration:
https://www.mail-archive.com/es-discuss@mozilla.org/msg11287.html
gramma disambiguation
https://www.mail-archive.com/es-discuss@mozilla.org/msg11245.html
labelled statements
https://www.mail-archive.com/es-discuss@mozilla.org/msg11258.html
prior art:
https://mail.mozilla.org/pipermail/es-discuss/2011-June/014893.html
https://mail.mozilla.org/pipermail/es-discuss/2011-June/014933.html
waldemar's consdiderations about statements as expressions
https://mail.mozilla.org/pipermail/es-discuss/2011-June/014898.html