Bug Report

Current Behavior
When the object has specified a [Symbol.hasInstance] method, helpers.instanceof does not cast the return result to boolean

Input Code

• REPL or Repo link if applicable: The REPL can not load @babel/[email protected] due to a 404 error.

var qux = {};
qux[Symbol.hasInstance]= function () { return NaN };
helpers.instanceof(0, qux);
// actual: returns NaN;
// expected: returns false;

Expected behavior/code
Per 12.10.4Runtime Semantics: InstanceofOperator ( V, target ), we should cast the return result to boolean.

Environment

• Babel version(s): 7.5.0
• Node/npm version: npm 5
• OS: macOS 10.14.5
• Monorepo: N.A.
• How you are using Babel: Reading the source code

Possible Solution
An PR is on the way.

Additional context/Screenshots
N.A.