# Changelog

> **Tags:**
> - [Breaking Change]
> - [Spec Compliancy]
> - [New Feature]
> - [Bug Fix]
> - [Documentation]
> - [Internal]
> - [Polish]

> Semver Policy: https://github.com/babel/babylon#semver

_Note: Gaps between patch versions are faulty, broken or test releases._

See the [Babel Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md) for the pre-6.8.0 version Changelog.

## v6.11.3 (2016-10-01)

### :eyeglasses: Spec Compliancy

Add static errors for object rest (#149) ([@danez](https://github.com/danez))

> https://github.com/sebmarkbage/ecmascript-rest-spread

Object rest copies the *rest* of properties from the right hand side `obj` starting from the left to right.

```js
let { x, y, ...z } =  { x: 1, y: 2, z: 3 };
// x = 1
// y = 2
// z = { z: 3 }
```

#### New Syntax Errors:

**SyntaxError**: The rest element has to be the last element when destructuring (1:10)
```bash
> 1 | let { ...x, y, z } = { x: 1, y: 2, z: 3};
    |           ^
# Previous behavior:
# x = { x: 1, y: 2, z: 3 }
# y = 2
# z = 3
```

Before, this was just a more verbose way of shallow copying `obj` since it doesn't actually do what you think.

**SyntaxError**: Cannot have multiple rest elements when destructuring (1:13)

```bash
> 1 | let { x, ...y, ...z } = { x: 1, y: 2, z: 3};
    |              ^
# Previous behavior:
# x = 1
# y = { y: 2, z: 3 }
# z = { y: 2, z: 3 }
```

Before y and z would just be the same value anyway so there is no reason to need to have both.

**SyntaxError**: A trailing comma is not permitted after the rest element (1:16)

```js
let { x, y, ...z, } = obj;
```

The rationale for this is that the use case for trailing comma is that you can add something at the end without affecting the line above. Since a RestProperty always has to be the last property it doesn't make sense.

---

get / set are valid property names in default assignment (#142) ([@jezell](https://github.com/jezell))

```js
// valid
function something({ set = null, get = null }) {}
```

## v6.11.2 (2016-09-23)

### Bug Fix

- [#139](https://github.com/babel/babylon/issues/139) Don't do the duplicate check if not an identifier (#140) @hzoo

```js
// regression with duplicate export check
SyntaxError: ./typography.js: `undefined` has already been exported. Exported identifiers must be unique. (22:13)
  20 | 
  21 | export const { rhythm } = typography;
> 22 | export const { TypographyStyle } = typography
```

Bail out for now, and make a change to account for destructuring in the next release.

## 6.11.1 (2016-09-22)

### Bug Fix
- [#137](https://github.com/babel/babylon/pull/137) - Fix a regression with duplicate exports - it was erroring on all keys in `Object.prototype`. @danez

```javascript
export toString from './toString';
```

```bash
`toString` has already been exported. Exported identifiers must be unique. (1:7)
> 1 | export toString from './toString';
    |        ^
  2 |
```

## 6.11.0 (2016-09-22)

### Spec Compliancy (will break CI)

- Disallow duplicate named exports ([#107](https://github.com/babel/babylon/pull/107)) @kaicataldo

```js
// Only one default export allowed per module. (2:9)
export default function() {};
export { foo as default };

// Only one default export allowed per module. (2:0)
export default {};
export default function() {};

// `Foo` has already been exported. Exported identifiers must be unique. (2:0)
export { Foo };
export class Foo {};
```

### New Feature (Syntax)

- Add support for computed class property names ([#121](https://github.com/babel/babylon/pull/121)) @motiz88

```js
// AST
interface ClassProperty <: Node {
  type: "ClassProperty";
  key: Identifier;
  value: Expression;
  computed: boolean; // added
}
```

```js
// with "plugins": ["classProperties"]
class Foo {
  [x]
  ['y']
}

class Bar {
  [p]
  [m] () {}
}
 ```

### Bug Fix

- Fix `static` property falling through in the declare class Flow AST ([#135](https://github.com/babel/babylon/pull/135)) @danharper

```js
declare class X {
    a: number;
    static b: number; // static
    c: number; // this was being marked as static in the AST as well
}
```

### Polish

- Rephrase "assigning/binding to rvalue" errors to include context ([#119](https://github.com/babel/babylon/pull/119)) @motiz88

```js
// Used to error with:
// SyntaxError: Assigning to rvalue (1:0)

// Now:
// Invalid left-hand side in assignment expression (1:0)
3 = 4

// Invalid left-hand side in for-in statement (1:5)
for (+i in {});
```

### Internal

- Fix call to `this.parseMaybeAssign` with correct arguments ([#133](https://github.com/babel/babylon/pull/133)) @danez
- Add semver note to changelog ([#131](https://github.com/babel/babylon/pull/131)) @hzoo

## 6.10.0 (2016-09-19)

> We plan to include some spec compliancy bugs in patch versions. An example was the multiple default exports issue.

### Spec Compliancy

* Implement ES2016 check for simple parameter list in strict mode ([#106](https://github.com/babel/babylon/pull/106)) (Timothy Gu)

> It is a Syntax Error if ContainsUseStrict of FunctionBody is true and IsSimpleParameterList of FormalParameters is false. https://tc39.github.io/ecma262/2016/#sec-function-definitions-static-semantics-early-errors

More Context: [tc39-notes](https://github.com/rwaldron/tc39-notes/blob/master/es7/2015-07/july-29.md#611-the-scope-of-use-strict-with-respect-to-destructuring-in-parameter-lists)

For example:

```js
// this errors because it uses destructuring and default parameters
// in a function with a "use strict" directive
function a([ option1, option2 ] = []) {
  "use strict";
}
 ```

The solution would be to use a top level "use strict" or to remove the destructuring or default parameters when using a function + "use strict" or to.

### New Feature

* Exact object type annotations for Flow plugin ([#104](https://github.com/babel/babylon/pull/104)) (Basil Hosmer)

Added to flow in https://github.com/facebook/flow/commit/c710c40aa2a115435098d6c0dfeaadb023cd39b8

Looks like:

```js
var a : {| x: number, y: string |} = { x: 0, y: 'foo' };
```

### Bug Fixes

* Include `typeParameter` location in `ArrowFunctionExpression` ([#126](https://github.com/babel/babylon/pull/126)) (Daniel Tschinder)
* Error on invalid flow type annotation with default assignment ([#122](https://github.com/babel/babylon/pull/122)) (Dan Harper)
* Fix Flow return types on arrow functions ([#124](https://github.com/babel/babylon/pull/124)) (Dan Harper)

### Misc

* Add tests for export extensions ([#127](https://github.com/babel/babylon/pull/127)) (Daniel Tschinder)
* Fix Contributing guidelines [skip ci] (Daniel Tschinder)

## 6.9.2 (2016-09-09)

The only change is to remove the `babel-runtime` dependency by compiling with Babel's ES2015 loose mode. So using babylon standalone should be smaller.

## 6.9.1 (2016-08-23)

This release contains mainly small bugfixes but also updates babylons default mode to es2017. The features for `exponentiationOperator`, `asyncFunctions` and `trailingFunctionCommas` which previously needed to be activated via plugin are now enabled by default and the plugins are now no-ops.

### Bug Fixes

- Fix issues with default object params in async functions ([#96](https://github.com/babel/babylon/pull/96)) @danez
- Fix issues with flow-types and async function ([#95](https://github.com/babel/babylon/pull/95)) @danez
- Fix arrow functions with destructuring, types & default value ([#94](https://github.com/babel/babylon/pull/94)) @danharper
- Fix declare class with qualified type identifier ([#97](https://github.com/babel/babylon/pull/97)) @danez
- Remove exponentiationOperator, asyncFunctions, trailingFunctionCommas plugins and enable them by default ([#98](https://github.com/babel/babylon/pull/98)) @danez

## 6.9.0 (2016-08-16)

### New syntax support

- Add JSX spread children ([#42](https://github.com/babel/babylon/pull/42)) @calebmer

(Be aware that React is not going to support this syntax)

```js
<div>
  {...todos.map(todo => <Todo key={todo.id} todo={todo}/>)}
</div>
```

- Add support for declare module.exports ([#72](https://github.com/babel/babylon/pull/72)) @danez

```js
declare module "foo" {
  declare module.exports: {}
}
```

### New Features

- If supplied, attach filename property to comment node loc. ([#80](https://github.com/babel/babylon/pull/80)) @divmain
- Add identifier name to node loc field ([#90](https://github.com/babel/babylon/pull/90)) @kittens

### Bug Fixes

- Fix exponential operator to behave according to spec ([#75](https://github.com/babel/babylon/pull/75)) @danez
- Fix lookahead to not add comments to arrays which are not cloned ([#76](https://github.com/babel/babylon/pull/76)) @danez
- Fix accidental fall-through in Flow type parsing. ([#82](https://github.com/babel/babylon/pull/82)) @xiemaisi
- Only allow declares inside declare module ([#73](https://github.com/babel/babylon/pull/73)) @danez
- Small fix for parsing type parameter declarations ([#83](https://github.com/babel/babylon/pull/83)) @gabelevi
- Fix arrow param locations with flow types ([#57](https://github.com/babel/babylon/pull/57)) @danez
- Fixes SyntaxError position with flow optional type ([#65](https://github.com/babel/babylon/pull/65)) @danez

### Internal

- Add codecoverage to tests @danez
- Fix tests to not save expected output if we expect the test to fail @danez
- Make a shallow clone of babel for testing @danez
- chore(package): update cross-env to version 2.0.0 ([#77](https://github.com/babel/babylon/pull/77)) @greenkeeperio-bot
- chore(package): update ava to version 0.16.0 ([#86](https://github.com/babel/babylon/pull/86)) @greenkeeperio-bot
- chore(package): update babel-plugin-istanbul to version 2.0.0 ([#89](https://github.com/babel/babylon/pull/89)) @greenkeeperio-bot
- chore(package): update nyc to version 8.0.0 ([#88](https://github.com/babel/babylon/pull/88)) @greenkeeperio-bot

## 6.8.4 (2016-07-06)

### Bug Fixes

- Fix the location of params, when flow and default value used ([#68](https://github.com/babel/babylon/pull/68)) @danez

## 6.8.3 (2016-07-02)

### Bug Fixes

- Fix performance regression introduced in 6.8.2 with conditionals ([#63](https://github.com/babel/babylon/pull/63)) @danez

## 6.8.2 (2016-06-24)

### Bug Fixes

- Fix parse error with yielding jsx elements in generators `function* it() { yield <a></a>; }` ([#31](https://github.com/babel/babylon/pull/31)) @eldereal
- When cloning nodes do not clone its comments ([#24](https://github.com/babel/babylon/pull/24)) @danez
- Fix parse errors when using arrow functions with an spread element and return type `(...props): void => {}` ([#10](https://github.com/babel/babylon/pull/10)) @danez
- Fix leading comments added from previous node ([#23](https://github.com/babel/babylon/pull/23)) @danez
- Fix parse errors with flow's optional arguments `(arg?) => {}` ([#19](https://github.com/babel/babylon/pull/19)) @danez
- Support negative numeric type literals @kittens
- Remove line terminator restriction after await keyword @kittens
- Remove grouped type arrow restriction as it seems flow no longer has it @kittens
- Fix parse error with generic methods that have the name `get` or `set` `class foo { get() {} }` ([#55](https://github.com/babel/babylon/pull/55)) @vkurchatkin
- Fix parse error with arrow functions that have flow type parameter declarations `<T>(x: T): T => x;` ([#54](https://github.com/babel/babylon/pull/54)) @gabelevi

### Documentation

- Document AST differences from ESTree ([#41](https://github.com/babel/babylon/pull/41)) @nene
- Move ast spec from babel/babel ([#46](https://github.com/babel/babylon/pull/46)) @hzoo

### Internal

- Enable skipped tests ([#16](https://github.com/babel/babylon/pull/16)) @danez
- Add script to test latest version of babylon with babel ([#21](https://github.com/babel/babylon/pull/21)) @danez
- Upgrade test runner ava @kittens
- Add missing generate-identifier-regex script @kittens
- Rename parser context types @kittens
- Add node v6 to travis testing @hzoo
- Update to Unicode v9 ([#45](https://github.com/babel/babylon/pull/45)) @mathiasbynens

## 6.8.1 (2016-06-06)

### New Feature

- Parse type parameter declarations with defaults like `type Foo<T = string> = T`

### Bug Fixes
- Type parameter declarations need 1 or more type parameters.
- The existential type `*` is not a valid type parameter.
- The existential type `*` is a primary type

### Spec Compliancy
- The param list for type parameter declarations now consists of `TypeParameter` nodes
- New `TypeParameter` AST Node (replaces using the `Identifier` node before)

```
interface TypeParameter <: Node {
  bound: TypeAnnotation;
  default: TypeAnnotation;
  name: string;
  variance: "plus" | "minus";
}
```

## 6.8.0 (2016-05-02)

#### New Feature

##### Parse Method Parameter Decorators ([#12](https://github.com/babel/babylon/pull/12))

> [Method Parameter Decorators](https://goo.gl/8MmCMG) is now a TC39 [stage 0 proposal](https://github.com/tc39/ecma262/blob/master/stage0.md).

Examples:

```js
class Foo {
  constructor(@foo() x, @bar({ a: 123 }) @baz() y) {}
}

export default function func(@foo() x, @bar({ a: 123 }) @baz() y) {}

var obj = {
  method(@foo() x, @bar({ a: 123 }) @baz() y) {}
};
```

##### Parse for-await statements (w/ `asyncGenerators` plugin) ([#17](https://github.com/babel/babylon/pull/17))

There is also a new node type, `ForAwaitStatement`.

> [Async generators and for-await](https://github.com/tc39/proposal-async-iteration) are now a [stage 2 proposal](https://github.com/tc39/ecma262#current-proposals). 

Example:

```js
async function f() {
  for await (let x of y);
}
```