`@lib: ES6` on fourslash test case breaks tests

[saschanaz]

TypeScript Version: master

Repro:

1. Insert // @lib: ES6 on test/fourslash/commentsFunctionExpression.ts
2. Run jake runtests t=commentsFunctionExpression

Expected behavior:

The test should run well

Actual behavior:

Numbers unexpectedly becomes any:

AssertionError: At 14: quick info text: expected 'var assigned: (s: string) => any' to equal 'var assigned: (s: string) => number'

Probably the test code does not correctly check /// <reference /> comment in lib.d.ts files but not sure how can it be fixed.

[jakebailey]

Just looking at old issues; this doesn't break anymore.