On Sep 18, 2012, at 7:27 AM, Andreas Rossberg wrote:
> On 17 September 2012 19:51, Allen Wirfs-Brock <[email protected]> wrote: >> >> On Sep 17, 2012, at 12:37 PM, Luke Hoban wrote: >>> >>> These are good questions. Paul will be attending the TC39 meeting this >>> week, and can likely talk to specific details. High level though, we >>> statically eliminate the TDZ checks for references to 'let' within the same >>> closure body as the declaration. >>> >> >> The other major check that I would expect to be significant, is whether a >> inner function that references an outer TDZ binding is (potentially) called >> before initialization of the binding. EG: >> >> { >> function f(){return x} >> f(); //TDZ check of x in f can not be eliminated >> let x=1; >> } >> >> { >> function f(){return x} >> let x=1; //TDZ check of x in f should be eliminated >> f(); >> } > > Unfortunately, detecting this case in general requires significant > static analysis, since f might be called indirectly through other > functions (even ignoring the case where f is used in a first-class > manner). > Yes but but there are fairly simple heuristics that approximate that result, for example: if no function calls dominate the initialization of x then TDZ checks will never need to be made for x _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
