.github/CHANGELOG-v5.md
# Babel v5 Changelog
## 5.8.26
* **Internal**
* Republish to get fix for runtime `typeof-react-element` helper.
## 5.8.25
* **Internal**
* Rename `define` method to avoid webpack assuming those files are AMD.
## 5.8.24
* **Spec Compliance**
* Updated `optimisation.react.inlineElements` transformer to React 0.14 output. Thanks [@spicyj](https://github.com/spicyj)!
* **Polish**
* Add support for evaluating more static nodes. Thanks [@hzoo](https://github.com/hzoo)!
## 5.8.23
* **Bug Fix**
* Fix a bug where pushed scope bindings weren't properly being registered.
## 5.8.22
* **Bug Fix**
* Fix bug causing regexes to cause a syntax error after a block.
* **Internal**
* Expose `File`.
## 5.8.21
* **New Feature**
* Add support for Flow export types.
* **Bug Fix**
* Fix flow type annotations on object properties being lost.
* Fix bug effecting nested arrow functions.
* Check valid `export default` `function`/`class` token when parsing export default before converting to a declaration to avoid turning expressions into declarations.
* **Polish**
* Add an exception to non-existent bindings when checking if we need to wrap block scoping blocks in a closure.
* Make comment retainment for multiple replacement nodes more predictable.
* **Internal**
* Remove `operator` property from `AssignmentPattern` nodes.
* Update `es7.asyncFunctions` and `es7.objectRestSpread` to stage 2.
## 5.8.13-5.8.20
**The CHANGELOG was broken for these releases. Git tags were not pushed in the correct order and are therefore incorrect. It's recommended you NOT use any versions within this range.**
* **New Feature**
* Add `es6.spec.modules` transformer.
* **Bug Fix**
* Don't register export declarations as a module binding.
* Register import bindings to the specifier instead of the declaration.
* `export *` should not export `default`.
* Clear `rawValue from JSX attribute values to avoid outputting the raw source verbatim.
* Add support for boolean flow literals.
* Fix bug where files that babel can compile weren't being written when ignored with the `--copy-files` flag.
* Create new raw identifiers instead of cloning the original user one when exploding export specifiers to fix source map issues resulting in incorrect locations.
* Break on hitting a terminator paren triggering character to avoid pushing multiple starting parens.
* Consider comment starting character to be a terminatorless separator to avoid starting comments breaking terminatorless nodes.
* **Internal**
* Use `json5` for parsing `.babelrc` files and `JSON` for `package.json`.
* Update Regenerator dependency to `0.8.35`.
* Remove flow types from being scope tracked.
* **Polish**
* Only register export declarations in scope tracking if they're of a valid type.
* Only output code frame and message on syntax errors in CLI.
* Set decorated initialisers that have no `initialiser` to `undefined`.
* Optimise common `typeof` cases in `es6.spec.symbols` transformer.
## 5.8.12
* **Bug Fix**
* Fix bug in lookahead causing decorators to be cleared.
## 5.8.11
* **Bug Fix**
* Check if module options are nully instead of falsy to allow empty strings as `moduleRoot` etc.
* Fix bug where reassigning the rest parameter wouldn't result in a deoptimisation.
## 5.8.9
* **Bug Fix**
* Fix issue in parser where the flow plugin wasn't using state to refer to whether it as in a type or not causing lookaheads to cause breakages.
## 5.8.8
* **Bug Fix**
* Fix comments not being attached if they're touching the start of their node.
## 5.8.7
* Never published, environment issues, again.
## 5.8.6
* **Bug Fix**
* Remove `rawValue` for JSX inner text.
## 5.8.5
* **Polish**
* Rewrite parentheses insertion for terminatorless nodes such as `BreakStatement` to be much more stable and cleaner.
* Use `Object.setPrototypeOf` and fallback to `__proto__` in `inherits` helper.
## 5.8.2-5.8.4
Issues with publish process.
## 5.8.1
* **Bug Fix**
* Fix regression where async arrow functions couldn't have type annotation parameters.
* Output type annotations of type instantiation parameters.
* **Polish**
* Prepend to highest loop when performing rest parameter allocation optimisation.
* Add comment attachment to parser.
* Add support for retaining inner comments of empty blocks.
## 5.8.0
* Never released due to publish environment issues.
## 5.7.4
* **Bug Fix**
* Fix comments containg `@flow` being completely removed from output rather than just the specific directive.
## 5.7.3
* **Bug Fix**
* Add shim file for broken file path that old versions of the CLI would attempt to use.
## 5.7.2
* **Bug Fix**
* Fix performance issue in code generator when comment columns would attempt to match up in `compact` mode causing large amounts of whitespace.
* Fix single line comments not outputting a newline in `compact` mode.
* **Polish**
* Add support for flow return types for arrow functions.
## 5.7.1
* **Bug Fix**
* Add back mistakenly removed `replaceWithSourceString` method.
## 5.7.0
* **Bug Fix**
* Deopt on spread elements when performing array destructuring unpack optimisation.
* **New Feature**
* Add `shouldPrintComment` option to control comment output.
* Add `.babelignore` file to be consistent with other tools.
* Allow `.babelrc` configs to be specified via `package.json`.
* **Polish**
* Don't ignore comments when using `compact: true` option.
* Add support for Flow `import typeof`.
* Fix incorrect inheritance method position when using loose mode classes and constructor isn't the first item.
* **Internal**
* Completely fork Acorn with `babylon`.
* Rewrite build system to accommodate for multiple packages.
## 5.6.17
* **Bug Fix**
* Fix `CodeGenerator.findCommonStringDelimiter` causing a stack overflow.
## 5.6.16
* **Internal**
* Fix `recast` version to avoid pulling in a newer version.
* **New Feature**
* Add support for functions in `util.shouldIgnore`.
* **Polish**
* Strip flow directives in flow transformer.
* Add a check for out of bounds default parameters, drastically improving performance and removes engine deoptimisations.
* Various performance optimisations by [@samccone](https://github.com/samccone) 💅✨
* Delay `this` assignment when referencing this inside an arrow function pre-bare super in derived class constructors.
* Split up class body pushing if the constructor is in the wrong order.
* **Bug Fix**
* Fix hoisting of `ForInStatement` `init` variables in `system` module formatter.
* `PathHoister`: Don't hoist to the same function as their original paths function parent.
* `PathHoister`: Push each violation paths ancestry to the breakOnScopePaths collection to avoid constant hoisting to nested paths.fix tail call recursion on functions with less arguments than parameters.
* Disallow `super.*` before `super()` in derived class constructors.
* Properly regenerate scope for replaced nodes. Thanks [@loganfsmyth](https://github.com/loganfsmyth)!
* Move up template literal simplification logic to avoid breaking on single elements.
## 5.6.13-5.6.15
* Setting up automatic Travis releases.
## 5.6.12
* **Bug Fix**
* Fix finding parent for top-level shadowed functions.
## 5.6.11
** **Internal**
* Merge `es6.parameters.rest` and `es6.parameters.default` transformers. See commit [c0fd4c1f9e0b18231f585c4fa793e4cb0e01aed1](https://github.com/babel/babel/commit/c0fd4c1f9e0b18231f585c4fa793e4cb0e01aed1) for more info.
## 5.6.10
* **Bug Fix**
* Fix faulty internal require check.
* **Polish**
* Add support for trailing commas in arrow function parameter lists.
## 5.6.8
* **Bug Fix**
* Fix binary expressions colliding with unary expression operators in compact mode.
* Fix node properties being set to `null` when using computed properties.
## 5.6.7
* **Bug Fix**
* Fix hoisting of `ForXStatement` `left` `var`s when inserting a block scoping IIFE.
* **Polish**
* Combine all leading computed property initialisers into the root object in loose mode.
* **Internal**
* Deprecate returning of replacement strings from visitor methods.
## 5.6.6
* **Bug Fix**
* Fix weird parser bug where `void` type annotations were being parsed as keywords causing the tokeniser to lose track of context.
## 5.6.5
* **Bug Fix**
* Fix nested functions causing rest parameter optimisation to not properly detect when it should deopt on a reference.
* **Internal**
* Update Regenerator `0.8.31`.
## 5.6.4
* **Internal**
* Add `ParenthesizedExpression` node type.
## 5.6.3
* **Bug Fix**
* Fix rest parameter array allocation loop being incorrectly aliased.
## 5.6.2
* **Bug Fix**
* Fix method key literals not turning into computed member expression in loose mode.
* Elect rest parameters in spread element position as candidates instead of replacing them in place.
## 5.6.0
* **Bug Fix**
* Fix istanbul interop for register hook when registering for non-existence extension.
* Fix super class constructor call differing for no constructor in derived classes.
* Disable module import receiver when in loose mode.
* Fix duplicate filenames when using `babel` CLI when passing multiple matching patterns.
* Register labels as bindings to fix undeclared variable checks.
* **Polish**
* Remove unnecessary string binary expressions when transforming template literals.
* Support module live bindings in arbitrary positions not in Program statement position.
* Throw error when attempting to replace a `Program` root node with another node not of type `Program`.
* Optimise rest parameters in spread element position and allocate rest array at the earliest common ancestor of all references.
* Generate original number representation when value was not changed.
* Check for invalid binding identifiers when generating inferred method names.
* Don't terminate CLI when watching files fail compilation on init.
* **New Feature**
* Add new plugin API.
* **Internal**
* Split react displayName addition into a plugin.
* Add check for `JSXMemberExpression` to `t.isReferenced`.
* Move `validation.undeclaredVariableCheck` transformer up.
* Start great core-to-plugin exodus.
* Add `BindingIdentifier` virtual type.
* Hidden class optimisations.
* Array allocation optimisations.
* Update `regenerator`.
* Update `js-tokens`.
* Sync with upstream Acorn.
## 5.5.8
* **Internal**
* Remove extremely unprofessional and harsh error message for those hotlinking to `resolve-rc`.
## 5.5.7
* **Bug Fix**
* Push newline after decorators when doing code gen.
* Rewriting error handling to normalise options before merging them.
* Remove duplicate keys in `alias-keys.json` causing errors in strict mode.
* Fix `$ babel --help` not showing optional transformers as such.
* **New Feature**
* Add `auxiliaryCommentBefore` and `auxiliaryCommentAfter` options.
## 5.5.6
* **Bug Fix**
* Fix `let` binding collision in loop head not properly replacing `AssignmentExpression`s.
## 5.5.5
* **Bug Fix**
* Fix `file.opts` not being set before `file.log.deprecate` was called causing a `ReferenceError` as it was checking for a property on it.
## 5.5.4
* **Bug Fix**
* Add back missing `shouldIgnore` check.
* Log message on deprecated options rather than throw an error.
* Fix name of `auxiliaryComment` option when attempting Istanbul interop in `babel/register`.
## 5.5.3
* **Bug Fix**
* Fix weird state bug when traversing overa `node` `ClassProperty` instead of `path` in the `es6.classes` transformer.
## 5.5.2
* **Bug Fix**
* Fix `NodePath#isPure` on `Property` nodes.
* Use cwd instead of entry file directory when working out relative directory for `babel/register`.
* **Internal**
* Add scary warning for those few who choose to use the WIP experimental transformers.
## 5.5.1
* **Bug Fix**
* Remove `ClassProperty` nodes always in the `Flow` transformer. This is fine now since class properties aren't supported in any engine that supports classes but the `es7.classProperties` transformer will need to be updated in the future to desugar to ES6 classes instead of relying on the `es6.classes` transformer from being ran.
## 5.5.0
* **Bug Fix**
* Allow pushing declarations to `SwitchStatement`s.
* Fix `minification.removeDebugger` to remove `DebuggerStatement`s rather than `ExpressionStatement`s with an identifier of `debugger`.
* Check LHS in `ForInStatement` and `ForOfStatement` for constant violations.
* Register function `id` as a reference when naming methods to avoid collisions.
* Support key literals when checking for the existence of `displayName` property when attempting to add it for `React.createClass`.
* Remove `ExportDefaultSpecifier` check from `t.isDefaultSpecifier`.
* Don't consider `JSXIdentifier` HTML tag identifiers to be references.
* **Polish**
* Update `minification.deadCodeElimination` transformer to remove all statements after completion statements.
* Update `minification.deadCodeElimination` transformer to not inline single used bindings that exist in different scopes.
* When performing Istanbul interop in `babel/register`, add the auxiliary comment `"istanbul ignore text"` to get more accurate coverage.
* Add `--nolazy` argument to `babel-node`.
* Add support for `cluster` forking.
* Perform scope tracking in a single pass instead of multiple.
* Smarten up type inferrence and resolution to support the whole array of language constructs.
* Optimise module metadata retrieval into a single pass.
* Ignore trailing commas when inferring newlines.
* Rename `minification.inlineExpressions` transformer to `minification.constantFolding`.
* Check path relative to entry file when checking to see if we're inside `node_modules` when using `babel/register`.
* Upgrade `regenerator`.
## 5.4.7
* **Bug Fix**
* Don't consider `JSXAttribute` `names` to be valid `ReferencedIdentifier`s.
## 5.4.6
* **Bug Fix**
* Fix `spec.functionName` transformer incorrectly attempting to rename a binding that doesn't exist as it's a global.
* **Internal**
* Deprecate custom module formatters.
## 5.4.5
* **Bug Fix**
* Add `JSXIdentifier` as a valid `ReferencedIdentifier` visitor virtual type.
* Ignore `CallExpression` `_prettyCall` when the `retainLines` option is enabled.
* Inherit comments to new declaration node when exploding module declarations.
* Fix `es6.tailCall` transformer failing on calls that exceed the max parameters of the function.
## 5.4.4
* **Bug Fix**
* Fix bug where replacing variable declarations in the head of a `for` loop would turn them into `ExpressionStatement`s.
* Fix renaming of assignment expressions that were non-identifiers ie. patterns.
* Force space before `class` `id` to avoid breaking named classes when using `compact` mode.
* Add assignment pattern explosion to avoid initial duplicate nodes.
* Ignore this and arguments when performing TCO on shadowed functions.
* **Polish**
* Rename `sourceMapName` option to `sourceMapTarget`. Thanks [@getify](https://github.com/getify)!
* Better detection of completion records, ignore those in `Function`s.
* Clarified descriptions of the options that are enabled by default.
* Resolve `\`babel-plugin-${name}\`` plugin names **before** just checking the `name`. Thanks [@jquense](https://github.com/jquense)!
* Update AMD module formatter to add import default remapping.
## 5.4.3
* **Bug Fix**
* Fix `module` being incorrectly rewritten when used as in an export declaration.
* When performing single-reference inlining, ensure that the single reference isn't a child of the binding itself.
* Fix a bug in `minification.deadCodeElimination` where a new binding instance was being created for local class bindings instead of just inheriting the parent one.
* Fix bug with paren printing in `compact` and `retainLines` mode where a left paren was already printed before catching up.
* **Internal**
* Handle contexts for paths much better. This will ensure that the path node location info is in sync.
## 5.4.2
* **Polish**
* `ignore` and `only` patterns are now **very** liberal. The pattern can now exist anywhere in the path.
## 5.4.1
* **Bug Fix**
* Add missing `slash` dependency. Thanks [@browncolyn](https://github.com/browncolyn)!
* **Polish**
* Clean up `shouldIgnore` algorithm to work how you'd expect rather than being a hacky piece of shit. It now crawls the entire path, checking each section of it against the input ignore/only patterns. This means that the pattern `foo` will ignore the paths `foo/bar.js`, `bar/foo` etc.
## 5.4.0
* **New Feature**
* Added [function bind syntax](https://github.com/zenparsing/es-function-bind) behind stage 0. Thanks [@RReverser](https://github.com/rreverser)!
* Added `env` option. Especially handy when using the `.babelrc`.
* **Bug Fix**
* Fix files not properly being ignored when `babel.transform` ignores them when using `$ babel`.
* Fix scope tracking registering loop head bindings to their `VariableDeclaration` instead of `VariableDeclarator`.
* **Polish**
* Normalise path separators for souce map paths when using `$ babel`.
* Rework `PathHoister` to ignore global references and to not deopt on reassignments to referenced bindings, instead it tries to hoist to the highest scope.
* Added missing exponential operator inlining. Thanks [@nkt](https://github.com/nkt)!
* Optimise `regenerator` transformer. Thanks [@benjamn](https://github.com/benjamn)!
## 5.3.3
* **Bug Fix**
* Fix `minification.deadCodeElimination` transformer incorrectly trying to inline import declarations.
* Fix `minification.inlineExpression` transformer getting into an infinite loop.
## 5.3.2
* **Bug Fix**
* Fix patterns not being considered when hoisting variables in the `es6.blockScoping` transformer.
## 5.3.1
* **Bug Fix**
* Fix unique export specifiers not being cloned when exploding class and function exports,
* **Polish**
* Turn import remaps to sequence expressions to remove their context and improve performance.
## 5.3.0
**Speeeeeeed**
* **Spec Compliance**
* Allow trailing param commas for methods when using the `es7.trailingCommas` transformer.
* **Bug Fix**
* Fix `es6.blockScoping` transformer not properly ignoring `break` in `SwitchCase`.
* Fix lookahead context saving to avoid weird tokenizer state.
* Explode duplicate identifiers in export/import specifiers and property shorthand to create unique objects.
* Skip loose mode for class methods when they have decorators.
* When removing nodes, share their comments with their siblings.
* Properly hoist temp param declarations when doing TCO.
* **Internal**
* Add `--harmony_generators` flag to `$ babel-node`.
* Internal AST traversals have been minimised **drastically**. Transformers have been grouped together which means entire tree traversals are much fewer. Visiting nodes is now also skipped if the traversal context can detect that the handler is a noop. This sames precious cycles as it avoids constructing traversal paths and creating a new traversal context. See issues [#1472](https://github.com/babel/babel/issues/1472) and [#1486](https://github.com/babel/babel/issues/1486) for related discussion.
* **Polish**
* Move many `utility` transformers to `minification`.
## 5.2.17
* **Bug Fix**
* Fix auxiliary comments not properly being attached to function declaration helpers.
* Add `Super` node type to `ast-types` patch.
* Ignore parameter bindings when attempting to inline them in the `minification.deadCodeElimination` transformer.
* Correct `extensions` arguments when using the Babel CLI.
## 5.2.16
* **Bug Fix**
* Fix plugins being disabled when using the whitelist.
* Fix correct function scope being passed to `nameMethod.property` when inferring the function name for class methods.
* Fix incorrect extensions reference causing weird issues when using the Babel CLI.
* Fix destructuring param reference replacements not inheriting from their original param.
* **Spec Compliance**
* Fix order that method decorators are ran in.
## 5.2.15
* **Bug Fix**
* Fix initializer descriptor add attempt if it doesn't exist.
## 5.2.14
* **Bug Fix**
* Fix bug with initializer decorators where the descriptors weren't being defined if there was no `initializer` property.
* **Internal**
* Expose `retainLines` option to CLI.
* Fix `retainLines` option not being taken into consideration when doing multiple variable declaration declarators generation.
* Expose minified and unminified copies of dist scripts.
## 5.2.13
* **Bug Fix**
* Fix `ExportDeclaration`s being incorrectly removed when using the `utility.deadCodeElimination` transformer.
* Fix position of `utility` transformers.
* **New Feature**
* Add built-in `esquery` support.
* **Internal**
* Consolidate notion of "virtual types".
## 5.2.12
* **Polish**
* Make UID generation based on module declarations **much** nicer.
* **Internal**
* Remove internal check for traversal path replacement of self. This is a pattern that **could** come up in the wild and it could lead to pretty nasty code and may lead to internal regressions as the test coverage isn't 100% :( Instead, just put it in the fast path.
## 5.2.11
* **Internal**
* Rename `getModuleName` option to `getModuleId`, doh.
## 5.2.10
* **Bug Fix**
* Fix numerous issues in `replaceWithSourceString`. Thanks [@pangratz](https://github.com/pangratz)!
* **New Feature**
* Add `getModuleName` option. Thanks [@jayphelps](https://github.com/jayphelps)!
## 5.2.9
* **Bug Fix**
* Fix `_blockHoist` transformer incorrectly sorting nodes on shitty environments that aren't spec compliant in their key order.
* Fix broken `parse` API method reference to an undeclared import.
## 5.2.7
* **Bug Fix**
* Move `utility.deadCodeElimination` transformer up to avoid race conditions.
* Fix shorthand property scope binding renaming.
* **Polish**
* Turn helper variable declarations into function declarations if possible.
* **Internal**
* Removed native inheritance support from classes.
* Added `replaceWithSourceString` path API.
* Split up `es3.propertyLiterals` and `es3.memberExpressionLiterals` transformers to `minification.propertyLiterals` and `es3.memberExpressionLiterals`.
## 5.2.6
* **Internal**
* Fix transformer aliases being accidentally set as deprecated ones.
* Expose `Pipeline` as `TransformerPipeline` instead.
## 5.2.5
* **Bug Fix**
* Fix `parse` API not adding all the correct pipeline transformers.
## 5.2.4
* **Bug Fix**
* Fix race condition with the Node API being loaded awkwardly and not being able to initialise itself when used in the browser.
* **Internal**
* Expose `transform.pipeline`.
## 5.2.3
* **Bug Fix**
* Fix plugin containers being called with an undefined import. Thanks [@timbur](https://github.com/timbur)!
* Allow Flow object separators to be commas. Thanks [@monsanto](https://github.com/monsanto)!
* Add missing `Statement` and `Declaration` node aliases to flow types.
## 5.2.2
* **Internal**
* Allow `util.arrayify` to take arbitrary types and coerce it into an array.
## 5.2.1
* **Bug Fix**
* Fix regression in `node/register` that caused `node_modules` to not be ignored.
## 5.2.0
* **Bug Fix**
* Fix plugin strings splitting arbitrarily on `:` which caused full paths on Windows to fail as they include `:` after the drive letter.
* Call class property `initializer`s with their target instead of their descriptor.
* Fix `ignore` and `only` not properly working on Windows path separators. Thanks [@stagas](https://github.com/stagas)!
* Fix `resolveRc` running on files twice causing issues. Thanks [@lukescott](https://github.com/lukescott)!
* Fix shorthand properties not correctly being target for `isReferenced` checks. Thanks [@monsanto](https://github.com/monsanto)!
* **Polish**
* Allow passing an array of globs to `babel/register` `only` and `ignore` options. Thanks [@Mark-Simulacrum](https://github.com/Mark-Simulacrum)!
* When inferring function names that collide with upper bindings, instead of doing the wrapper, instead rename them.
* Consider constant-like variable declaration functions to always refer to themselves so TOC can be performed.
* Process globs manually when using `$ babel` as some shells such as Windows don't explode them. Thanks [@jden](https://github.com/jden)!
* Add alternative way to execute plugins via a closure that's called with the current Babel instance.
* **Internal**
* Remove multiple internal transformers in favor of directly doing things when we need to. Previously, declarations such as `_ref` that we needed to create in specific scopes were done at the very end via the `_declarations` transformer. Now, they're done and added to the scope **right** when they're needed. This gets rid of the crappy `_declarations` property on scope nodes and fixes the crappy regenerator bug where it was creating a new `BlockStatement` so the declarations were being lost.
* Rework transformer traversal optimisation. Turns out that calling a `check` function for **every single node** in the AST is ridiculously expensive. 300,000 nodes timesed by ~30 transformers meant that it took tens of seconds to perform while it's quicker to just do the unnecessary traversal. Seems obvious in hindsight.
* **New Feature**
* Add `jscript` transformer that turns named function expressions into function declarations to get around [JScript's horribly broken function expression semantics](https://kangax.github.io/nfe/#jscript-bugs). Thanks [@kondi](https://github.com/kondi)!
* Add `@@hasInstance` support to objects when using the `es6.spec.symbols` transformer.
* Add `retainLines` option that retains the line (but not the columns!) of the input code.
## 5.1.13
* **Polish**
* Remove symbol check from `defineProperty` helper.
## 5.1.12
* **Bug Fix**
* Fix `resolveModuleSource` not being ran on `ExportAllDeclaration`s.
* Fix `.babelrc` being resolved multiple times when using the require hook.
* Fix parse error on spread properties in assignment position.
* Fix `externalHelpers` option being incorrectly listed as type `string`.
* **Internal**
* Upgrade `core-js` to `0.9.0`.
* **Spec Compliance**
* Fix object decorators not using the `initializer` pattern.
* Remove property initializer descriptor reflection.
## 5.1.11
* **Bug Fix**
* Memoise and bind member expression decorators.
* Move JSX children cleaning to opening element visitor. Fixes elements not being cleaned in certain scenarios.
* Consider `SwitchStatement`s to be `Scopable`.
* Fix `bluebirdCoroutines` calling `interopRequireWildcard` before it's defined.
* Add space to `do...while` code generation.
* Validate `super` use before `this` on `super` exit rather than entrance.
* **Polish**
* Add Babel name to logger.
## 5.1.10
* **Bug Fix**
* Remove `makePredicate` from acorn in favor of an `indexOf`.
* Remove statements to expression explosion when inserting a block statement.
* **Internal**
* Remove runtime compatibility check.
## 5.1.9
* **Bug Fix**
* Fix class property initializers with `undefined` values not being correctly writable.
* Fix self inferring generators incorrectly causing a stack error.
* Fix default export specifiers not triggering AMD `module` argument inclusion.
* Fix assignments not having their module references properly remapped.
* **Internal**
* Upgrade to latest `acorn`.
* **Polish**
* Make invalid LHS pattern error messages nicer.
## 5.1.8
* **Bug Fix**
* Only make parenthesized object pattern LHS illegal.
## 5.1.7
* **Internal**
* Add `parse` node API.
## 5.1.6
* **Bug Fix**
* Fix `runtime` built-in catchall not properly checking for local variables.
## 5.1.5
* **Internal**
* Bump `core-js` version.
## 5.1.4
* **Polish**
* Add missing `Reflect` methods to runtime transformer.
## 5.1.3
* **Internal**
* Switch entirely to vanilla regenerator.
* Clean up and make the parsing of decorators stateless.
* **Bug Fix**
* Don't do TCO on generators and async functions.
* Add missing `core-js` runtime definitions.
## 5.1.2
* **Bug Fix**
* Add `getIterator` and `isIterable` to `babel-runtime` build script.
## 5.1.1
* **Bug Fix**
* Add missing runtime symbol definitions.
## 5.1.0
* **Bug Fix**
* Fix super reference when using decorators.
* Don't do array unpack optimisation when member expressions are present.
* Add missing descriptors for undecorated class properties.
* Don't consider `arguments` and `eval` valid function names when doing function name inferrence.
* Fix scope tracking of constants in loop heads.
* Parse `AwaitExpression` as a unary instead of an assignment.
* Fix regex evaluation when attempting static evaluation.
* Don't emit tokens when doing a lookahead.
* Add missing `test` declaration to `utility.deadCodeElimination` transformer.
* **Internal**
* Upgrade `regenerator` to the latest and use my branch with the hope of eventually switching to vanilla regenerator.
* Add support for the replacement of for loop `init`s with statements.
* Upgrade dependencies.
* **Polish**
* When adding the scope IIFE when using default parameters, don't shadow the function expression, just `apply` `this` and `arguments` if necessary.
* Use path basename as non-default import fallback.
* **New Feature**
* Add [trailing function comma proposal](https://github.com/jeffmo/es-trailing-function-commas). Thanks [@AluisioASG](https://github.com/AluisioASG)!
* Add support for object literal decorators.
* Make core-js modular when using the `runtime` transformer.
## 5.0.12
* **Bug Fix**
* Fix incorrect remapping of module references inside of a function id redirection container.
## 5.0.11
* **Bug Fix**
* Fix new `for...of` loops not properly inheriting their original loop.
* **Internal**
* Disable scope instance cache.
* **Polish**
* Allow comments in `.babelrc` JSON.
## 5.0.9
* **Polish**
* Use `moduleId` for UMD global name if available.
* **Bug Fix**
* Fix UMD global `module` variable shadowing the `amd`/`common` `module` variable.
* Fix Flow param type annotation regression.
* Fix function name collision `toString` wrapper. Thanks [@alawatthe](https://github.com/alawatthe)!
## 5.0.8
* **Bug Fix**
* Fix falsy static class properties not being writable.
* Fix block scoping collisions not properly detecting modules and function clashes.
* Skip `this` before `super` for derived constructors on functions.
## 5.0.7
* **New Feature**
* Add `--ignore` and `--only` support to the CLI.
* **Bug Fix**
* Remove `HOMEPATH` environment variable from home resolution in `babel/register` cache.
* **Internal**
* Disable WIP path resolution introducing infinite recursion in some code examples.
* **Polish**
* Add live binding to CommonJS default imports.
## 5.0.6
* **Bug Fix**
* Fix mangling of import references that collide with properties on `Object.prototype`.
* Fix duplicate declarations incorrectly being reported for `var`.
## 5.0.5
* **Internal**
* Upgrade `core-js`.
* **Bug Fix**
* Fix arrays not being supported in `util.list`.
## 5.0.4
* **Polish**
* Check for top level `breakConfig` in `resolveRc`.
## 5.0.3
* **Bug Fix**
* Make relative location absolute before calling `resolveRc`.
* **Internal**
* Switch to global UID registry.
* Add `breakConfig` option to prevent Babel from erroring when hitting that option.
## 5.0.1
* **Bug Fix**
* Fix duplicate declaration regression.
* Fix not being able to call non-writable methods.
## 5.0.0
* **New Feature**
* Decorators based on [@wycat's](https://github.com/wycats) [stage 1 proposal](https://github.com/wycats/javascript-decorators).
* Class property initializers based on [@jeffmo's](https://github.com/jeffmo) [stage 0 proposal](https://gist.github.com/jeffmo/054df782c05639da2adb).
* Export extensions based on [@leebyron's](https://github.com/leebyron) [stage 1 proposal](https://github.com/leebyron/ecmascript-more-export-from).
* UMD module formatter now supports globals.
* Add `es3.runtime`, `optimisation.react.inlineElements` and `optimisation.react.constantElements` transformers.
* Add stage option that replaces the experimental one.
* Allow ES7 transformer to be enabled via `optional` instead of only via `stage`.
* Infer string quotes to use in the code generator.
* Consider `export { foo as default };` to be the same as `export default foo;`.
* Add `nonStandard` option that can be set to `false` to remove parser support for JSX and Flow.
* Add `jsxPragma` option.
* Automatically generate CLI options based on internal API options.
* Add support for `.babelrc` on absolute paths.
* Plugin API!
* **Internal**
* Export `options` in browser API.
* Rewritten parser.
* Don't block hoist when runtime transformer is enabled in system module formatter.
* Rewritten the internal traversal and node replacement API to use "paths" that abstracts out node relationships.
* **Polish**
* JSX output is now more inline with the official JSX transformer.
* Hoist block scoping IIFE - this improves memory usage and performance.
* Better IIFE detection - references are now checked to see if they're referencing the binding we're searching for.
* Check for import reassignments in constants transformer.
* Make method definitions with expression bodies illegal.
* Save register cache on tick instead of `SIGINT`.
* Enable strict mode on babel-node eval flag.
* **Bug Fixes**
* Add support for live bindings. This change also increases the reliability of export specifier renaming.
* Add support for super update and non equals assignment expressions.
* Rename shadow constructor binding in classes.
* Seed next iteration bindings with previous fresh bindings when reassigning loop block scoped variables.
* Fix new expression spread referencing the wrong constructor.
* Call `resolveModuleSource` on dynamic imports.
* Added `param` to list of duplicate declaration kinds.
* **Breaking Changes**
* The Babel playground has been removed.
* ES7 Abstract References have been removed.
* Experimental option has been removed in favor of a stage option.
* Rename `returnUsedHelpers` to `metadataUsedHelpers`.