dart2js will migrate slowly to modern JavaScript.
The --legacy-javascript flag causes emitted code to be compatible with
IE11, our only supported non-modern target. This is a temporary flag
until IE11 is removed from support.
The negative flag --no-legacy-javascript allows the code to be
incompatible with legacy browsers and, over time, be improved to take
advantage of modern JavaScript features.
Initially --no-legacy-javascript will use some minimal features that
are incompatible with IE11 as a 'trip-wire' to ensure that
--legacy-javascript is always used for IE11. dart2js analytics can
then be used to assess how much --legacy-javascript is used. (The
'trip-wire' unsupported feature is unguarded use of JavaScript
Symbols.)
The default at this change is --legacy-javascript so that this change
is non-breaking. The default will be changed soon to
--no-legacy-javascript.
Change-Id: Ic13461362a5fa80293fb66b112945d1404a64a03
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/139867
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Stephen Adams
afbce123fa