On Jan 24, 2009, at 4:51 PM, Mark Miller wrote:
The current spec language allows the global eval property to be, in
effect, either mutable or not, benefiting no one. If we need to allow
correct programs to be able to mutate it (in an initial environment in
which it has not yet been frozen), then we should change the spec to
require it to be initially mutable, so that correct programs can rely
on this.
ES3 already requires eval to be a mutable global property, chapter 15
intro:
Every other property described in this section has the attribute
{ DontEnum } (and no others) unless otherwise specified.
Postel's Law means real code depends on this. Proving it is impossible
but you can't cite absence of evidence to prove evidence of absence of
eval overwriting.
The idea of changing eval's attributes seems unmotivated, since we
don't need to incompatibly change ES3 to preserve the "operator eval"
behavior everyone wants. Unless there is a real problem not solved by
the notions in the current spec (based on some implementations and on
ES4) then we should not change global property attributes. There's too
much opportunity for incompatible (silent failure to overwrite)
behavior.
/be
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