Simple object destructuring, such as `let {a,b} = o`, is less efficient
than the equivalent assignments `let a = o.a; let b = o.b`. This is
because it does a nil check of `o` before the assignments. However, this
nil check is not strictly necessary for simple (i.e. non-computed) names,
as there will be an equivalent nil check on the first access to o in
`o.a`. For computed names the computation is unfortunately obervable.
So, we can elide the nil check when the first property (if any) of the
destructuring target is a non-computed name. This messes a bit with our
error messages, so we re-use the CallPrinter to also find destructuring
assignment based errors, and fiddle with the error message there. As
a side-effect, we also get out the object name in the AST, so we can
output a slightly nicer error message.
Change-Id: Iafa858e27ed771a146cd3ba57903cc73bb46951d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1773254
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63453}
1fba044154