Status/Thoughts on Guards?

Brendan Eich brendan at
Tue Aug 19 23:23:50 PDT 2014

Jonathan Barronville wrote:
> +1 for ... some 
> really good research.

Yes, it's good.

> As Mark said, though, it's more likely we'll get a fight than anything 
> productive from such a conversation, which is quite unfortunate :( .

Best thing already happening is TypeScript with its embrace-and-extend 
approach to JS. I'm sure Anders et al. are tracking TS* and Safe 
TypeScript, so I expect we'll see fruits of the MSR work in product soon 

This then has a shot of making a cowpath for TC39 to pave. It's not as 
long as a shot, done via TypeScript + JS evolution, as the alternative 
you and Mark point to: a big _a priori_ type systems fight in TC39. Who 
wants that?

Alternatives include pluggable annotation syntax, or an evolution of 
Dart (Ecma TC52) + JS, but these look less likely to me to go into 
Harmony-era JS at the moment. Dart diverged too much, and pluggable 
syntax is a cop-out.


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