Sorry for the inaccurate shorthand; maybe that should read that SpiderMonkey supports it. Eric Faust of SpiderMonkey is a co-champion of the proposal, and spoke against implicit PTC at the March 2016 TC39 meeting. It&#x27;s hard to get much stronger in support of a proposal than being a champion, and Eric works for Mozilla. From that discussion, it also sounded like there was support from the Mozilla devtools team as well.<p>I&#x27;m interested in getting everyone&#x27;s point of view. We&#x27;ve been discussing pros and cons at <a href="https:&#x2F;&#x2F;github.com&#x2F;tc39&#x2F;proposal-ptc-syntax&#x2F;issues" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;tc39&#x2F;proposal-ptc-syntax&#x2F;issues</a> and <a href="https:&#x2F;&#x2F;github.com&#x2F;tc39&#x2F;ecma262&#x2F;issues&#x2F;535" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;tc39&#x2F;ecma262&#x2F;issues&#x2F;535</a> , and it&#x27;d be great to have your input, including the overturning-prior-consensus issues you raised in committee and anything else that comes to mind.<p>EDIT: How do you like the new wording &quot;For these reasons, the V8 team strongly support denoting proper tail calls by special syntax. There is a pending TC39 proposal called syntactic tail calls to specify this behavior, co-championed by committee members from Mozilla and Microsoft.&quot; ?