Improve REPL display of String values

[scabug]

Copied from SUGGEST-30:

In Scala REPL (interactive interpreter), type this:

scala> Set(1, "1.2")
res11: scala.collection.immutable.Set[Any] = Set(1, 1.2)

The result does not put a quote on "1.2". Then the user cannot easily see what type each member is in the set. In addition, for the following:

scala> Set(1, "1.2 ")
res15: scala.collection.immutable.Set[Any] = Set(1, "1.2 ")

Quotes are added for string with leading/trailing whitespaces. This adds inconsistency. Also considering the following:

scala> Set(1, "1.2, 55")
res18: scala.collection.immutable.Set[Any] = Set(1, 1.2, 55)

Isn't the result confusing?

Please consider always adding quotes on strings in REPL result. Thank you.

PS: Original google group post for this issue is here:
https://groups.google.com/forum/#!topic/scala-user/xiXpEsCtnoA

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8603?orig=1
Reporter: @som-snytt
Affected Versions: 2.11.0
See #6592

[scabug]

@som-snytt said:
Example confusion, compounded by quoting.

[scabug]

Li Haoyi (lihaoyi) said:
This is fixed in the Ammonite REPL

@  Set(1, "1.2")
res8: scala.collection.immutable.Set[Any] = Set(1, 1.2)
@ Set(1, "1.2 ")
res9: scala.collection.immutable.Set[Any] = Set(1, 1.2 )
@ Set(1, "1.2, 55")
res10: scala.collection.immutable.Set[Any] = Set(1, 1.2, 55)
@ Set("1", "1.2")
res11: scala.collection.immutable.Set[java.lang.String] = Set("1", "1.2")
@ Set("1", "1.2 ")
res13: scala.collection.immutable.Set[java.lang.String] = Set("1", "1.2 ")
@ Set(1, 1.2)
res12: scala.collection.immutable.Set[Double] = Set(1.0, 1.2)

As you can see, Set[Any] behavior still isn't great, but most people don't deal with Anys much anyway. Set[T] for any strongly-typed T is pretty-printed properly in the same way a literal would be written