SI-8680 Stream.addString is too eager

[Ichoran]

Used the standard method of sending out two iterators, one twice as fast as the others, to avoid hanging on .force, .hasDefiniteSize, and .addString.

.addString appends a "..." as the last element if it detects a cycle. It knows how to print the cycle length, but there's no good way to specify what you want right now, so it's not used.

Added tests in t8680 that verify that cyclic streams give the expected results.

scala/bug#8680

[adriaanm]

Ping @Ichoran:

test.bc:
     [echo] Checking backward binary compatibility for scala-library (against 2.11.0)
     [mima] Found 3 binary incompatibiities
     [mima] ===============================
     [mima]  * synthetic method
     [mima]    scala$collection$immutable$Stream$$loop$6(Int,Int,scala.Function1)scala.collection.immutable.Stream
     [mima]    in object scala.collection.immutable.Stream does not have a correspondent in
     [mima]    new version
     [mima]  * synthetic method
     [mima]    scala$collection$immutable$Stream$$loop$5(Int,scala.collection.immutable.Stream,java.lang.Object)scala.collection.immutable.Stream
     [mima]    in class scala.collection.immutable.Stream does not have a correspondent in
     [mima]    new version
     [mima]  * synthetic method
     [mima]    scala$collection$immutable$Stream$$loop$4(scala.collection.immutable.Set,scala.collection.immutable.Stream)scala.collection.immutable.Stream
     [mima]    in class scala.collection.immutable.Stream does not have a correspondent in
     [mima]    new version
     [mima] Generated filter config definition
     [mima] ==================================
     [mima] 
     [mima]     filter {
     [mima]         problems=[
     [mima]             {
     [mima]                 matchName="scala.collection.immutable.Stream.scala$collection$immutable$Stream$$loop$6"
     [mima]                 problemName=MissingMethodProblem
     [mima]             },
     [mima]             {
     [mima]                 matchName="scala.collection.immutable.Stream.scala$collection$immutable$Stream$$loop$5"
     [mima]                 problemName=MissingMethodProblem
     [mima]             },
     [mima]             {
     [mima]                 matchName="scala.collection.immutable.Stream.scala$collection$immutable$Stream$$loop$4"
     [mima]                 problemName=MissingMethodProblem
     [mima]             }
     [mima]         ]
     [mima]     }
     [mima] 

[Ichoran]

@adriaanm - Yeah, I meant to talk to you about this. These are inner recursive methods that nobody should ever call or know about. What is the policy with these? I couldn't keep the same interface anyway, due to different requirements for the loops. I can put dead loops back in just to keep the formal method list the same. Or is it okay to drop these since nobody should use them except the body of methods that I've changed (in otherwise binary compatible ways)?

[adriaanm]

Yeah, since these methods are effectively private, we can just add them to the mima whitelist.

[lrytz]

LGTM