Class double-bind

Brendan Eich brendan at mozilla.org
Tue Mar 3 11:51:37 UTC 2015


Claude Pache wrote:
> A simple solution is to make:
>
>      class Foo { /* ... */ }
>
> equivalent to:
>
>      const Foo = class Foo { /* ... */ }
>
> instead of the equivalent desugaring with `let`.

The ES6 design has "classes as sugar", which is an imprecise slogan, but 
useful. For some reason we settled on a mutable outer binding in block 
scope: let not const. That "some reason" may have been the expectation 
that classes desugar to prototypal 
function-as-constructor-with-prototype-properties lowerings, but still: 
no reason given ES6 const and let to prefer let.

I suspect it'll be hard to change anything for ES6 at this stage, 
especially to make class bind a const instead of a let binding -- but 
your point still stands:

>   That way, anyone who want to play with a same-named external binding must be explicit about their intention:
>
>      let Foo = class { /* ... */ } // one binding
>      let Foo = class Foo { /* .... */ } // two bindings

Anyone who wants to support replacement-for-wrapping will have to use 
the first form.

Let's see if this becomes the norm, on that basis. I hope it doesn't, 
because if so, we picked the wrong (two-binding-not-one) desugaring.

/be


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