jshint / jshint / 2455

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Pull #2927

travis-ci

[[FEAT]] Error for literals on rhs of `instanceof`

This patch adds a new error that is used when a literal is found on the
right-hand side of the `instanceof` infix operator. A warning is used when a
function declaration is found.

Literals generate errors:

    x instanceof 0;
    x instanceof '';
    x instanceof null;
    x instanceof undefined;
    x instanceof {};
    x instanceof [];
    x instanceof /./;
    x instanceof ``;

Function declarations generate warnings:

    x instanceof function() {};
    x instanceof function MyUnusableFunction() {};

But this is okay:

    x instanceof /x/.constructor;
    x instanceof "".constructor;

as per GH-2773

References:

    Closes GH-2777

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