#1401. [Patterns] Object pattern test added

[sgrekhov]

See dart-lang/language#2745

[eernstg]

Looks good. I considered patterns in a declaration context, and I believe we can have a test for that, too:

An _ in a declaration context is a wildcard (not a variable pattern introducing a variable named _), and it is also possible to use an object pattern in a declaration context. So we should be able to do something like this:

var SomeClass(v1: _, v2: x) = SomeClass(3, 4);

Yes, it's silly (we don't have to look up the value of v1, so we don't really need a mechanism that will allow us to look it up and then ignore it), but it could be used to look up the value of v1 and perform a type cast on it in order to have a dynamic error if it doesn't have that type. So it doesn't have to be silly in all scenarios to have a wildcard in a declaration.

[sgrekhov]

Added LanguageFeatures/Patterns/object_A07_t06.dart

[eernstg]

LGTM