no-extra-boolean-cast autofixer handles some Boolean() calls incorrectly

[not-an-aardvark]

Tell us about your environment

• ESLint Version: master
• Node Version: 7.4.0
• npm Version: 4.0.5

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

default

Please show your full configuration:

rules:
  no-extra-boolean-cast: error
parserOptions:
  ecmaVersion: 2015

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

I ran eslint theFile.js --fix on three different files:

// Case 1
!Boolean(...foo);

// Case 2
!Boolean(foo, bar());

// Case 3
!Boolean();

What did you expect to happen?

I expected the syntax of the files to be valid after autofixing

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

In the first two files, the code was autofixed to

// Case 1
!...foo;

// Case 2
!foo;

An error was thrown when running the command on the third file:

TypeError: Cannot read property 'type' of undefined
    at Object.getPrecedence (/path/to/eslint/lib/ast-utils.js:620:21)
    at Object.fix (/path/to/eslint/lib/rules/no-extra-boolean-cast.js:103:42)
    at RuleContext.report (/path/to/eslint/lib/rule-context.js:127:34)
    at EventEmitter.CallExpression (/path/to/eslint/lib/rules/no-extra-boolean-cast.js:97:29)
    at emitOne (events.js:96:13)
    at EventEmitter.emit (events.js:188:7)
    at NodeEventGenerator.enterNode (/path/to/eslint/lib/util/node-event-generator.js:39:22)
    at CodePathAnalyzer.enterNode (/path/to/eslint/lib/code-path-analysis/code-path-analyzer.js:607:23)
    at CommentEventGenerator.enterNode (/path/to/eslint/lib/util/comment-event-generator.js:98:23)
    at Controller.enter (/path/to/eslint/lib/eslint.js:928:36)

The first autofixed line is a syntax error, and the second autofixed line changes the behavior of the code (it no longer calls bar()).

To fix this, I think we need to avoid doing an autofix for no-extra-boolean-cast in the following cases:

• Boolean is called with more than one argument
• Boolean is called with a spread element as the first argument
• Boolean is called with no arguments. (Alternatively, we could just fix !Boolean() to true.)

[ljharb]

Why would anyone call Boolean with more than one argument?

Boolean() should be equivalent to Boolean(undefined), in other words, false.

[not-an-aardvark]

Why would anyone call Boolean with more than one argument?

¯\_(ツ)_/¯

Boolean() should be equivalent to Boolean(undefined), in other words, false.

Yes, but the rule only activates when the expression is negated to !Boolean() (since the Boolean call is then a useless cast), which would be true.