Brendan Eich wrote:
Kevin Smith wrote:
This makes for wtfjs additions, but they all seem non-wtf on
reflection (or did to us when Waldemar threw them up on a
whiteboard last week). By non-wtf, I mean anyone who groks that
yield is reserved only in function* can work them out.
The star after function really helps. ES5's "use strict" directive
prologue in the body applying to its left (even in ES5 --
duplicate formals are a strict error) is goofy.
Agree on all counts, but not quite understanding yet.
Say I'm parsing this, and the token stream is paused at the "#":
function(a = # yield
I assume that we're not un-reserving yield in strict mode. That
means that I don't know whether to treat `yield` as an identifier or
reserved word until I get to that goofy prologue.
Ouch, you're right. We can't handle this without backtracking.
Waldemar should weigh in.
Well, we can handle it. We know due to lack of * after function that
yield, whether reserved (due to "use strict"; in body prologue) or not,
can't be yield-the-operator. So it's either an identifier (no "use
strict";) or a reserved word (and an error due to lack of * after function).
So we parse it as an identifier, just as we parse duplicate formal
parameters. Then if we see "use strict", we must post-process the parse
tree and throw an error. Kind of a shame, but there it is.
At least reserving 'let' in ES5 strict did some good!
/be
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