Add support for Unicode 13 properties in regular expressions.
### Bug fixes
Use a loop to find line breaks, because the existing regexp search would overrun the end of the searched range and waste a lot of time in minified code.
## 8.6.0 (2021-11-18)
### Bug fixes
Fix a bug where an object literal with multiple `__proto__` properties would incorrectly be accepted if a later property value held an assigment.
### New features
Support class private fields with the `in` operator.
## 8.5.0 (2021-09-06)
### Bug fixes
Improve context-dependent tokenization in a number of corner cases.
Fix location tracking after a 0x2028 or 0x2029 character in a string literal (which before did not increase the line number).
Fix an issue where arrow function bodies in for loop context would inappropriately consume `in` operators.
Fix wrong end locations stored on SequenceExpression nodes.
Implement restriction that `for`/`of` loop LHS can't start with `let`.
### New features
Add support for ES2022 class static blocks.
Allow multiple input files to be passed to the CLI tool.
## 8.4.1 (2021-06-24)
### Bug fixes
Fix a bug where `allowAwaitOutsideFunction` would allow `await` in class field initializers, and setting `ecmaVersion` to 13 or higher would allow top-level await in non-module sources.
## 8.4.0 (2021-06-11)
### New features
A new option, `allowSuperOutsideMethod`, can be used to suppress the error when `super` is used in the wrong context.
## 8.3.0 (2021-05-31)
### New features
Default `allowAwaitOutsideFunction` to true for ECMAScript 2022 an higher.
Add support for the `d` ([indices](https://github.com/tc39/proposal-regexp-match-indices)) regexp flag.
## 8.2.4 (2021-05-04)
### Bug fixes
Fix spec conformity in corner case 'for await (async of ...)'.
## 8.2.3 (2021-05-04)
### Bug fixes
Fix an issue where the library couldn't parse 'for (async of ...)'.
Fix a bug in UTF-16 decoding that would read characters incorrectly in some circumstances.
## 8.2.2 (2021-04-29)
### Bug fixes
Fix a bug where a class field initialized to an async arrow function wouldn't allow await inside it. Same issue existed for generator arrow functions with yield.
## 8.2.1 (2021-04-24)
### Bug fixes
Fix a regression introduced in 8.2.0 where static or async class methods with keyword names fail to parse.
## 8.2.0 (2021-04-24)
### New features
Add support for ES2022 class fields and private methods.
## 8.1.1 (2021-04-12)
### Various
Stop shipping source maps in the NPM package.
## 8.1.0 (2021-03-09)
### Bug fixes
Fix a spurious error in nested destructuring arrays.
### New features
Expose `allowAwaitOutsideFunction` in CLI interface.
Make `allowImportExportAnywhere` also apply to `import.meta`.
## 8.0.5 (2021-01-25)
### Bug fixes
Adjust package.json to work with Node 12.16.0 and 13.0-13.6.
## 8.0.4 (2020-10-05)
### Bug fixes
Make `await x ** y` an error, following the spec.
Fix potentially exponential regular expression.
## 8.0.3 (2020-10-02)
### Bug fixes
Fix a wasteful loop during `Parser` creation when setting `ecmaVersion` to `"latest"`.
## 8.0.2 (2020-09-30)
### Bug fixes
Make the TypeScript types reflect the current allowed values for `ecmaVersion`.
Fix another regexp/division tokenizer issue.
## 8.0.1 (2020-08-12)
### Bug fixes
Provide the correct value in the `version` export.
## 8.0.0 (2020-08-12)
### Bug fixes
Disallow expressions like `(a = b) = c`.
Make non-octal escape sequences a syntax error in strict mode.
### New features
The package can now be loaded directly as an ECMAScript module in node 13+.
Update to the set of Unicode properties from ES2021.
### Breaking changes
The `ecmaVersion` option is now required. For the moment, omitting it will still work with a warning, but that will change in a future release.
Some changes to method signatures that may be used by plugins.
Make the string in the `version` export match the actual library version.
## 7.3.0 (2020-06-11)
### Bug fixes
Fix a bug that caused parsing of object patterns with a property named `set` that had a default value to fail.
### New features
Add support for optional chaining (`?.`).
## 7.2.0 (2020-05-09)
### Bug fixes
Fix precedence issue in parsing of async arrow functions.
### New features
Add support for nullish coalescing.
Add support for `import.meta`.
Support `export * as ...` syntax.
Upgrade to Unicode 13.
## 6.4.1 (2020-03-09)
### Bug fixes
More carefully check for valid UTF16 surrogate pairs in regexp validator.
## 7.1.1 (2020-03-01)
### Bug fixes
Treat `\8` and `\9` as invalid escapes in template strings.
Allow unicode escapes in property names that are keywords.
Don't error on an exponential operator expression as argument to `await`.
More carefully check for valid UTF16 surrogate pairs in regexp validator.
## 7.1.0 (2019-09-24)
### Bug fixes
Disallow trailing object literal commas when ecmaVersion is less than 5.
### New features
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.
## 7.0.0 (2019-08-13)
### Breaking changes
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.
## 6.3.0 (2019-08-12)
### New features
`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.
Disallow binding `let` in patterns.
### New features
Support bigint syntax with `ecmaVersion` >= 11.
Support dynamic `import` syntax with `ecmaVersion` >= 11.
Upgrade to Unicode version 12.
## 6.1.1 (2019-02-27)
### Bug fixes
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.
