## 5.4.1 (2018-02-02)

### Bug fixes

5.4.0 somehow accidentally included an old version of walk.js.

## 5.4.0 (2018-02-01)

### Bug fixes

Disallow duplicate or escaped flags on regular expressions.

Disallow octal escapes in strings in strict mode.

### New features

Add support for async iteration.

Add support for object spread and rest.

## 5.3.0 (2017-12-28)

### Bug fixes

Fix parsing of floating point literals with leading zeroes in loose mode.

Allow duplicate property names in object patterns.

Don't allow static class methods named `prototype`.

Disallow async functions directly under `if` or `else`.

Parse right-hand-side of `for`/`of` as an assignment expression.

Stricter parsing of `for`/`in`.

Don't allow unicode escapes in contextual keywords.

### New features

Parsing class members was factored into smaller methods to allow plugins to hook into it.

## 5.2.1 (2017-10-30)

### Bug fixes

Fix a token context corruption bug.

## 5.2.0 (2017-10-30)

### Bug fixes

Fix token context tracking for `class` and `function` in property-name position.

Make sure `%*` isn't parsed as a valid operator.

The `full` and `fullAncestor` walkers no longer visit nodes multiple times.

Allow shorthand properties `get` and `set` to be followed by default values.

Disallow `super` when not in callee or object position.

### New features

Support [`directive` property](https://github.com/estree/estree/compare/b3de58c9997504d6fba04b72f76e6dd1619ee4eb...1da8e603237144f44710360f8feb7a9977e905e0) on directive expression statements.

## 5.1.2 (2017-09-04)

### Bug fixes

Disable parsing of legacy HTML-style comments in modules.

Fix parsing of async methods whose names are keywords.

## 5.1.1 (2017-07-06)

### Bug fixes

Fix problem with disambiguating regexp and division after a class.

## 5.1.0 (2017-07-05)

### Bug fixes

Fix tokenizing of regexps in an object-desctructuring `for`/`of` loop and after `yield`.

Parse zero-prefixed numbers with non-octal digits as decimal.

Allow object/array patterns in rest parameters.

Don't error when `yield` is used as a property name.

Allow `async` as a shorthand object property.

Make the ES module version of the loose parser actually work.

### New features

Implement the [template literal revision proposal](https://github.com/tc39/proposal-template-literal-revision) for ES9.

New walker functions `full` and `fullAncestor`.

## 5.0.3 (2017-04-01)

### Bug fixes

Fix spurious duplicate variable definition errors for named functions.

## 5.0.2 (2017-03-30)

### Bug fixes

A binary operator after a parenthesized arrow expression is no longer incorrectly treated as an error.

## 5.0.0 (2017-03-28)

### Bug fixes

Raise an error for duplicated lexical bindings.

Fix spurious error when an assignement expression occurred after a spread expression.

Accept regular expressions after `of` (in `for`/`of`), `yield` (in a generator), and braced arrow functions.

Allow labels in front or `var` declarations, even in strict mode.

### Breaking changes

Parse declarations following `export default` as declaration nodes, not expressions. This means that class and function declarations nodes can now have `null` as their `id`.

## 4.0.11 (2017-02-07)

### Bug fixes

Allow all forms of member expressions to be parenthesized as lvalue.

## 4.0.10 (2017-02-07)

### Bug fixes

Don't expect semicolons after default-exported functions or classes,
even when they are expressions.

Check for use of `'use strict'` directives in non-simple parameter
functions, even when already in strict mode.

## 4.0.9 (2017-02-06)

### Bug fixes

Fix incorrect error raised for parenthesized simple assignment
targets, so that `(x) = 1` parses again.

## 4.0.8 (2017-02-03)

### Bug fixes

Solve spurious parenthesized pattern errors by temporarily erring on
the side of accepting programs that our delayed errors don't handle
correctly yet.

## 4.0.7 (2017-02-02)

### Bug fixes

Accept invalidly rejected code like `(x).y = 2` again.

Don't raise an error when a function _inside_ strict code has a
non-simple parameter list.

## 4.0.6 (2017-02-02)

### Bug fixes

Fix exponential behavior (manifesting itself as a complete hang for
even relatively small source files) introduced by the new 'use strict'
check.

## 4.0.5 (2017-02-02)

### Bug fixes

Disallow parenthesized pattern expressions.

Allow keywords as export names.

Don't allow the `async` keyword to be parenthesized.

Properly raise an error when a keyword contains a character escape.

Allow `"use strict"` to appear after other string literal expressions.

Disallow labeled declarations.

## 4.0.4 (2016-12-19)

### Bug fixes

Fix issue with loading acorn_loose.js with an AMD loader.

Fix crash when `export` was followed by a keyword that can't be
exported.

## 4.0.3 (2016-08-16)

### Bug fixes

Allow regular function declarations inside single-statement `if`
branches in loose mode. Forbid them entirely in strict mode.

Properly parse properties named `async` in ES2017 mode.

Fix bug where reserved words were broken in ES2017 mode.

## 4.0.2 (2016-08-11)

### Bug fixes

Don't ignore period or 'e' characters after octal numbers.

Fix broken parsing for call expressions in default parameter values
of arrow functions.

## 4.0.1 (2016-08-08)

### Bug fixes

Fix false positives in duplicated export name errors.

## 4.0.0 (2016-08-07)

### Breaking changes

The default `ecmaVersion` option value is now 7.

A number of internal method signatures changed, so plugins might need
to be updated.

### Bug fixes

The parser now raises errors on duplicated export names.

`arguments` and `eval` can now be used in shorthand properties.

Duplicate parameter names in non-simple argument lists now always
produce an error.

### New features

The `ecmaVersion` option now also accepts year-style version numbers
(2015, etc).

Support for `async`/`await` syntax when `ecmaVersion` is >= 8.

Support for trailing commas in call expressions when `ecmaVersion`
is >= 8.

## 3.3.0 (2016-07-25)

### Bug fixes

Fix bug in tokenizing of regexp operator after a function declaration.

Fix parser crash when parsing an array pattern with a hole.

### New features

Implement check against complex argument lists in functions that
enable strict mode in ES7.

## 3.2.0 (2016-06-07)

### Bug fixes

Improve handling of lack of unicode regexp support in host
environment.

Properly reject shorthand properties whose name is a keyword.

Don't crash when the loose parser is called without options object.

### New features

Visitors created with `visit.make` now have their base as _prototype_,
rather than copying properties into a fresh object.

Make it possible to use `visit.ancestor` with a walk state.

## 3.1.0 (2016-04-18)

### Bug fixes

Fix issue where the loose parser created invalid TemplateElement nodes
for unclosed template literals.

Properly tokenize the division operator directly after a function
expression.

Allow trailing comma in destructuring arrays.

### New features

The walker now allows defining handlers for `CatchClause` nodes.

## 3.0.4 (2016-02-25)

### Fixes

Allow update expressions as left-hand-side of the ES7 exponential
operator.

## 3.0.2 (2016-02-10)

### Fixes

Fix bug that accidentally made `undefined` a reserved word when
parsing ES7.

## 3.0.0 (2016-02-10)

### Breaking changes

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.

### Fixes

`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.

### New features

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.

## 2.7.0 (2016-01-04)

### Fixes

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.

## 2.6.4 (2015-11-12)

### Fixes

Fix crash in loose parser when parsing invalid object pattern.

### New features

Support plugins in the loose parser.

## 2.6.2 (2015-11-10)

### Fixes

Don't crash when no options object is passed.

## 2.6.0 (2015-11-09)

### Fixes

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.

### New features

Support parsing stdin in command-line tool.

## 2.5.2 (2015-10-27)

### Fixes

Fix bug where the walker walked an exported `let` statement as an
expression.

## 2.5.0 (2015-10-27)

### Fixes

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.