TypeScript Version: 2.0.3

It is very unclear how to effectively use the --lib compiler option. It appears there is a default set of libs that are included (i.e. when no --lib is specified). If any libs are specified with --lib, then it seems this default set gets replaced with the set you provide. I haven't been able to find any documentation on exactly what is in the default set.

Here's the issue I'm running into. I want to use the [default set] + es2015.collection. I've tried a number of things.

• --lib es2015.collection OR --lib es6 - Lots of errors because DOM isn't declared
• --lib es6,dom,scripthost,webworker - Several errors about duplicate signatures and declarations, e.g.
  lib.dom.d.ts(2145,5): error TS2375: Build: Duplicate number index signature.
lib.dom.d.ts(3772,14): error TS2403: Build: Subsequent variable declarations must have the same type. Variable 'srcElement' must be of type 'any', but here has type 'Element'.
• [no --lib option] - Can't use ES6 sets/maps.

Expected behavior:
Either the set of libs you can import needs to be disjoint, or the compiler should be able to handle duplicate declarations in these files.