Fix bug that accidentally made undefined a reserved word when
parsing ES7.
The default value of the ecmaVersion option is now 6 (used to be 5).
Support for comprehension syntax (which was dropped from the draft spec) has been removed.
let and 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.
When ecmaVersion is set to 7, Acorn will parse the exponentiation
operator (**).
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.
Stop allowing rest parameters in setters.
Make sure the loose parser always attaches a local property to
ImportNamespaceSpecifier nodes.
Disallow y rexexp flag in ES5.
Disallow \00 and \000 escapes in strict mode.
Raise an error when an import name is a reserved word.
Fix crash in loose parser when parsing invalid object pattern.
Support plugins in the loose parser.
Don't crash when no options object is passed.
Add await as a reserved word in module sources.
Disallow yield in a parameter default value for a generator.
Forbid using a comma after a rest pattern in an array destructuring.
Support parsing stdin in command-line tool.
Fix bug where the walker walked an exported let statement as an
expression.
Fix tokenizer support in the command-line tool.
In the loose parser, don't allow non-string-literals as import sources.
Stop allowing new.target outside of functions.
Remove legacy guard and guardedHandler properties from try nodes.
Stop allowing multiple __proto__ properties on an object literal in
strict mode.
Don't allow rest parameters to be non-identifier patterns.
Check for duplicate paramter names in arrow functions.