3.16.0 regression: padded-blocks autofix can generate incorrect code

[alangpierce]

Tell us about your environment

• ESLint Version: 3.16.0
• Node Version: 6.9.1
• npm Version: 3.10.8

What parser (default, Babel-ESLint, etc.) are you using?
default

Please show your full configuration:

module.exports = {
  rules: {
    "padded-blocks": ['error', 'never'],
  }
};

(This is the value specified by eslint-config-airbnb.)

What did you do? Please include the actual source code causing the issue.

I ran eslint --fix on this source code:

function f() { // a

  b;
}

What did you expect to happen?

I expected it to fix the formatting and generate correct code.

What actually happened? Please include the actual, raw output from ESLint.

eslint generated this output:

➜  eslint_test_3 git:(master) ./node_modules/.bin/eslint --fix test.js

/Users/alanpierce/code/eslint_test_3/test.js
  6:1  error  Parsing error: Unexpected token

✖ 1 problem (1 error, 0 warnings)

And the JS file was changed to have these contents:

function f() {
function f() { // a

  b;
}

This is a syntax error, so the file fails to parse after this change.

When I try this on eslint 3.15.0, it doesn't have any problems.

This is breaking the coffeelint example build for the decaffeinate project. The lexical_linter.js file has two static initClass lines near the start, which causes a syntax error. (The example builds are a bit like eslint-canary for the decaffeinate project, and one of the conversion steps is to run eslint --fix on the resulting JS code.)

[not-an-aardvark]

I can reproduce this, thanks for reporting.

Based on git bisect it was introduced in fcc38db.