Tell us about your environment

MacOS 10.14.5 (18F132)
zsh 5.3 (x86_64-apple-darwin18.0)

• ESLint Version: v6.0.1
• Node Version: v8.15.0
• npm Version: 6.9.0

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

Please show your full configuration:

module.exports = {
  "env": {
    "browser": true,
    "node": true,
    "es6": true,
  },
  "extends": [
    "eslint:recommended",
    "plugin:prettier/recommended",
  ],
  "globals": {
    "Atomics": "readonly",
    "SharedArrayBuffer": "readonly",
  },
  "parserOptions": {
    "ecmaVersion": 2018,
    "sourceType": "module",
  },
  "rules": {
    "no-unused-vars": ["error", {args: "none"}],
  },
}

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

No source, the bug happens even if the file is empty.

$ cat src/routes/blog/\[slug\].svelte
console.log('x',)
$ npx eslint src/routes/blog/\[slug\].svelte
No files matching 'src/routes/blog/[slug].svelte' were found.
$ npx eslint src/routes/blog/[slug].svelte
No files matching 'src/routes/blog/[slug].svelte' were found.
$ npx eslint src/routes/blog/\\[slug\\].svelte
No files matching 'src/routes/blog/\[slug\].svelte' were found.

What did you expect to happen?

That eslint would lint the file.

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

Eslint was unable to find the file.

Are you willing to submit a pull request to fix this bug?

I could give it a shot, but I'm probably not the best person to solve it.