Add a static `acorn` property to the `Parser` class that contains the entire module interface, to allow plugins to access the instance of the library that they are acting on.
Changes the node format for dynamic imports to use the `ImportExpression` node type, as defined in [ESTree](https://github.com/estree/estree/blob/master/es2020.md#importexpression).
Makes 10 (ES2019) the default value for the `ecmaVersion` option.
`sourceType: "module"` can now be used even when `ecmaVersion` is less than 6, to parse module-style code that otherwise conforms to an older standard.
## 6.2.1 (2019-07-21)
### Bug fixes
Fix bug causing Acorn to treat some characters as identifier characters that shouldn't be treated as such.
Fix issue where setting the `allowReserved` option to `"never"` allowed reserved words in some circumstances.
## 6.2.0 (2019-07-04)
### Bug fixes
Improve valid assignment checking in `for`/`in` and `for`/`of` loops.
Fix bug that caused parsing default exports of with names to fail.
## 6.1.0 (2019-02-08)
### Bug fixes
Fix scope checking when redefining a `var` as a lexical binding.
### New features
Split up `parseSubscripts` to use an internal `parseSubscript` method to make it easier to extend with plugins.
## 6.0.7 (2019-02-04)
### Bug fixes
Check that exported bindings are defined.
Don't treat `\u180e` as a whitespace character.
Check for duplicate parameter names in methods.
Don't allow shorthand properties when they are generators or async methods.
Forbid binding `await` in async arrow function's parameter list.
## 6.0.6 (2019-01-30)
### Bug fixes
The content of class declarations and expressions is now always parsed in strict mode.
Don't allow `let` or `const` to bind the variable name `let`.
Treat class declarations as lexical.
Don't allow a generator function declaration as the sole body of an `if` or `else`.
Ignore `"use strict"` when after an empty statement.
Allow string line continuations with special line terminator characters.
Treat `for` bodies as part of the `for` scope when checking for conflicting bindings.
Fix bug with parsing `yield` in a `for` loop initializer.
Implement special cases around scope checking for functions.
## 6.0.5 (2019-01-02)
### Bug fixes
Fix TypeScript type for `Parser.extend` and add `allowAwaitOutsideFunction` to options type.
Don't treat `let` as a keyword when the next token is `{` on the next line.
Fix bug that broke checking for parentheses around an object pattern in a destructuring assignment when `preserveParens` was on.
## 6.0.4 (2018-11-05)
### Bug fixes
Further improvements to tokenizing regular expressions in corner cases.
## 6.0.3 (2018-11-04)
### Bug fixes
Fix bug in tokenizing an expression-less return followed by a function followed by a regular expression.
Remove stray symlink in the package tarball.
## 6.0.2 (2018-09-26)
### Bug fixes
Fix bug where default expressions could fail to parse inside an object destructuring assignment expression.
## 6.0.1 (2018-09-14)
### Bug fixes
Fix wrong value in `version` export.
## 6.0.0 (2018-09-14)
### Bug fixes
Better handle variable-redefinition checks for catch bindings and functions directly under if statements.
Forbid `new.target` in top-level arrow functions.
Fix issue with parsing a regexp after `yield` in some contexts.
### New features
The package now comes with TypeScript definitions.
### Breaking changes
The default value of the `ecmaVersion` option is now 9 (2018).
Plugins work differently, and will have to be rewritten to work with this version.
The loose parser and walker have been moved into separate packages (`acorn-loose` and `acorn-walk`).
## 5.7.3 (2018-09-10)
### Bug fixes
Fix failure to tokenize regexps after expressions like `x.of`.
Better error message for unterminated template literals.
## 5.7.2 (2018-08-24)
### Bug fixes
Properly handle `allowAwaitOutsideFunction` in for statements.
Treat function declarations at the top level of modules like let bindings.
Don't allow async function declarations as the only statement under a label.
## 5.7.0 (2018-06-15)
### New features
Upgraded to Unicode 11.
## 5.6.0 (2018-05-31)
### New features
Allow U+2028 and U+2029 in string when ECMAVersion >= 10.
Allow binding-less catch statements when ECMAVersion >= 10.
Add `allowAwaitOutsideFunction` option for parsing top-level `await`.
## 5.5.3 (2018-03-08)
### Bug fixes
A _second_ republish of the code in 5.5.1, this time with yarn, to hopefully get valid timestamps.
## 5.5.2 (2018-03-08)
### Bug fixes
A republish of the code in 5.5.1 in an attempt to solve an issue with the file timestamps in the npm package being 0.
## 5.5.1 (2018-03-06)
### Bug fixes
Fix misleading error message for octal escapes in template strings.
## 5.5.0 (2018-02-27)
### New features
The identifier character categorization is now based on Unicode version 10.
Acorn will now validate the content of regular expressions, including new ES9 features.
## 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.
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.
### New features
Implement the [template literal revision proposal](https://github.com/tc39/proposal-template-literal-revision) for ES9.
## 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 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.
### New features
Visitors created with `visit.make` now have their base as _prototype_, rather than copying properties into a fresh object.
## 3.1.0 (2016-04-18)
### Bug fixes
Properly tokenize the division operator directly after a function expression.
Allow trailing comma in destructuring arrays.
## 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.
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.
## 2.6.2 (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.
## 2.5.0 (2015-10-27)
### Fixes
Fix tokenizer support in the command-line tool.
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.
