Inline parameters

[peey]

Q	A
Patch: Bug Fix?	no
Major: Breaking Change?	no
Minor: New Feature?	yes
Deprecations?	no
Spec Compliancy?	yes
Tests Added/Pass?	yes
Fixed Tickets	none
License	MIT
Doc PR	no
Dependency Changes	no

Add path.inlineParameters() for use in es2015-parameters and object-rest-spread plugins

• Moves all the function parameters to body in an arrayPattern initializer,
• Uses block scoping for the case of function declaration as a default argument or in case of a var redeclaration of a parameter binding in function body

Not Added:

• A way to convert the rest parameter. Since code for handling this already exists in es2015-parameters plugin, I think that's a better place for that logic.

[mention-bot]

@peey, thanks for your PR! By analyzing the history of the files in this pull request, we identified @hzoo, @existentialism and @boopathi to be potential reviewers.

[codecov]

Codecov Report

Merging #5751 into 7.0 will increase coverage by 0.1%.
The diff coverage is 95.83%.

@@            Coverage Diff            @@
##              7.0    #5751     +/-   ##
=========================================
+ Coverage   85.15%   85.25%   +0.1%     
=========================================
  Files         284      285      +1     
  Lines        9953    10025     +72     
  Branches     2776     2789     +13     
=========================================
+ Hits         8475     8547     +72     
+ Misses        977      974      -3     
- Partials      501      504      +3

Impacted Files	Coverage Δ
packages/babel-traverse/src/path/index.js	83.13% <ø> (ø)	⬆️
packages/babel-traverse/src/path/family.js	78.37% <100%> (+1.9%)	⬆️
packages/babel-traverse/src/path/parameters.js	95.23% <95.23%> (ø)
...bel-plugin-transform-es2015-classes/src/vanilla.js	91.06% <0%> (+0.42%)	⬆️
packages/babel-traverse/src/path/context.js	86.2% <0%> (+1.72%)	⬆️

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[buunguyen]

Would be great if you can update to use the newly merged minNodeVersion option and get rid of the node check & eval here and a few other tests in this PR.

[peey]

Thanks for adding that feature! I'll update my code asap :)

[jridgewell]

Why does this require an array destructuring?

[peey]

@jridgewell the idea is that instead of duplicating all destructing and rest/spread logic (in argument defaults) for parameters, we have a general function which would inline the parameters into the function body.

Then the code to handle array destructing and rest/spread could do the further processing.

[peey]

@loganfsmyth need your thoughts on this if you still think this is a good idea. After this we can proceed on incorporating it into object-rest-spread and the parameters transform to solve a lot of issues.