Fix: dot-notation autofix produces syntax errors for object called "let"

[not-an-aardvark]

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

[x] Bug fix

Tell us about your environment

• ESLint Version: master
• Node Version: 8.1.2
• npm Version: 5.0.3

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

default

Please show your full configuration:

rules:
  dot-notation: [error, { allowKeywords: false }]

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

var let = { if() { console.log('foo') } };
let.if();

What did you expect to happen?

I expected eslint --fix to not break the code.

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

The code was autofixed to invalid syntax:

var let = { if() { console.log('foo') } };
let["if"]();

What changes did you make? (Give an overview)

The dot-notation autofixer previously fixed code like let.if to let["if"]. However, this is a syntax error because a statement beginning with let[ is parsed as the start of a variable declaration, not a MemberExpression.

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

Nothing in particular

[eslintbot]

LGTM

[platinumazure]

LGTM. Should this apply to const as well?

[not-an-aardvark]

No, because unlike let, const is not a valid variable name.