Expanding on #150, this allows `unexpected()` to accept the expected token type instead of a message string.
This overload is then used in a couple more places (that independently implement a logic similar to `expect()`'s) to construct an `Unexpected token, expected FOO` message.
* Rephrase "assigning/binding to rvalue" error messages with context (#119)
* Fix code style in parser/lval.js
* istanbul ignore some unused branches in parser/lval.js
* Fix code style again in parser/lval.js
* Slightly simplify logic
* Implement ES2016 check for simple parameter list in strict mode
See e.g. ECMA-262 7.0 14.1.2:
> It is a Syntax Error if ContainsUseStrict of FunctionBody is true and
> IsSimpleParameterList of FormalParameters is false.
Similar clauses cover arrow functions, generator functions, methods, and
generator methods, as well as async functions and async arrow functions.
I'm extremely stupid and didn't commit as I go. To anyone reading this
I'm extremely sorry. A lot of these changes are very broad and I plan on
releasing Babel 6.0.0 today live on stage at Ember Camp London so I'm
afraid I couldn't wait. If you're ever in London I'll buy you a beer
(or assorted beverage!) to make up for it, also I'll kiss your feet and
give you a back massage, maybe.
