Expression Closures as Compliment to Arrow Functions

Brendan Eich brendan at
Thu Mar 26 01:08:09 UTC 2015

Isiah Meadows wrote:
> Would this be rectifiable with something like an unbound lambda type 
> syntax?

There's nothing to rectify -- could do m() expr; in classes as shorter 
form of m() { return expr; }, and similarly in object literals (, as 
separator, not ; as terminator).

What gates this concise body for method shorthand idea is strong sense 
it's worth the added complexity (syntax should be added only with clear 
and strong signal that it's needed, e.g. to provide a special form for 
new semantics that cannot be provided by an API). And then someone to do 
the work drafting an ES7 proposal.

What stopped thin-arrow function syntax when I got fat-arrow through 
TC39 was the idea that two arrows was a bridge too far. That sense might 
change with time user demand, but it's not something to rush. Anyway, 
thin arrow is not related to this thread.

> You could even make an analogous equivalent for classes. 

Sure, but why require thin arrow for method shorthand, when method 
requires unbound `this`? Allowing fat arrow seems a hazard with no real 
use case motivating it. In any case, grammatically we need no arrow at 
all. There's no grammar issues AFAICS with concise methods of the m() 
expr; form, provided expr is parsed as an AssignmentExpression and ; is 


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