[1] [WebIDL] Remove string constants ( (Anne van Kesteren 著, 2011-10-20 11:25:57 +09:00 版)) http://lists.w3.org/Archives/Public/public-script-coord/2011OctDec/0040.html

[2] Disallow constants to be null (#686) (saschanaz著, 2019-03-15 21:08:24 +09:00) https://github.com/heycam/webidl/commit/c57bdf88df351cbc0f2b76cf64fdb2a166d9d485

[3] Disallow constants to be null by saschanaz · Pull Request #686 · heycam/webidl (2020-01-12 11:45:30 +09:00) https://github.com/heycam/webidl/pull/686

[4] Investigate removing nullables from allowed constant types · Issue #448 · heycam/webidl (2020-01-12 11:46:36 +09:00) https://github.com/heycam/webidl/issues/448