On Nov 21, 2010, at 7:52 PM, Mark S. Miller wrote:
> On Sun, Nov 21, 2010 at 7:48 PM, Brendan Eich <[email protected]> wrote:
>> The reason I chose "::" over ":" is not for a love of "::". Alternative
>> suggestions appreciated! However, I avoided ":" so that we could guard
>> properties within object literals
>> <http://wiki.ecmascript.org/doku.php?id=strawman:guards#guarding_properties>.
>> I don't see a way to use ":" for that without confusion. The ES4 solution
>> -- that one can only annotate an object literal as a whole but not its
>> individual properties -- always seemed unpleasant.
>
> :: is strictly less pleasant, and really kind of "taken" due to the
> precedents I cited. The "less pleasant" point is the big one IMHO.
>
> Can we find something better than "::" that doesn't conflict with the ":" in
> the object literal syntax? As I said, I have no love for "::".
Annotating property names in object initialisers is a relatively infrequent
use-case -- a hard case that should not impose double the number of colons on
all annotated declarations (formal parameters, let/const/var, function return
types).
The ML-ish solution, which is forward compatible, is to parenthesize:
let typedObj = { (prop1:type1): value1, (prop2:type2): value2, ... };
The parentheses hurt too, but only this case. And it still may win to annotate
the entire ObjectLiteral sometimes, which would avoid (or move to one common
guard-type definition) the property-wise annotation overhead. Comments?
/be
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