Initialization in setupSpec for a @Shared field defined in trait is overridden

Originally reported on Google Code with ID 370

I've been playing with Spock and traits mix and I spotted an issue with @Shared field
declared in a trait. Following code fails:

class SharedTraitUsage extends Specification implements MySharedTrait {
def "should not restore inline assigned value on shared field defined in trait before
every test"() {
expect:
sharedValue == 11
}
}

trait MySharedTrait {
@Shared
int sharedValue = 12

def setupSpec() {
sharedValue = 11
}

with the error:

Condition not satisfied:

sharedValue == 11
| |
12 false

I started debugging AST transformations using `EmbeddedSpecification`, but I wasn't
able to find a clear way how to "fix" it. More details and a broken test I will put
as a pull request.

Reported by mszpak@wp.pl on 2014-07-14 21:32:29

Start with EmbeddedSpecification and the AST transformations involved in trait handling. Reproduce the SharedTraitUsage example with a regression test based on the reported setupSpec behavior. Done means the setupSpec assignment to sharedValue remains 11 instead of being restored to its inline value of 12.