Fix: operator-assignment crash on adjacent division assignment

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.
• The team has reached consensus on the changes proposed in this pull request. If not, I understand that the evaluation process will begin with this pull request and won't be merged until the team has reached consensus.

What is the purpose of this pull request? (put an "X" next to item)

[X] Bug fix

Tell us about your environment

• ESLint Version: 7.0.0-alpha.0
• Node Version: v12.14.0
• npm Version: v6.13.4

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

default

Please show your full configuration:

Configuration

module.exports = {
    parserOptions: {
        ecmaVersion: 2015
    },
};

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

/*eslint operator-assignment: ["error", "never"]*/

foo/=bar

Online Demo Link (v6.8.0 actual)

What did you expect to happen?

Not to crash.

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

SyntaxError: Unterminated regular expression
...
at Espree.tokenize
at Object.tokenize
at Object.canTokensBeAdjacent

What changes did you make? (Give an overview)

astUtils.canTokensBeAdjacent passes source code / to Espree.tokenize, which throws on that seeing a lone slash as an unterminated regex literal.

I changed the operator-assignment rule to pass a token-like object instead of a source code made up of an operator only.

Is there anything you'd like reviewers to focus on?

astUtils.canTokensBeAdjacent should be also fixed to account for / on the left side and comments or regex literals on the right side, as these cannot be adjacent (it would turn everything into a // line comment). I'll work on that in another PR.

[kaicataldo]

LGTM, thanks!

[yeonjuan]

LGTM, thanks!
I got it :). The newOperator was a string not a Token.

[kaicataldo]

Thanks for contributing!