The default value of the
ecmaScript option is now 6 (used to be 5).
Support for comprehension syntax (which was dropped from the draft
spec) has been removed.
yield are now “contextual keywords”, meaning you can
mostly use them as identifiers in ES5 non-strict code.
A parenthesized class or function expression after
export default is
now parsed correctly.
ecmaVersion is set to 7, Acorn will parse the exponentiation
The identifier character ranges are now based on Unicode 8.0.0.
Plugins can now override the
raiseRecoverable method to override the
way non-critical errors are handled.