StagedTuple changes

[biboudis]

Restore previous unapply and homogenize staged method names. I used the convention of putting the *Staged at the end.

• Decouple staged tuples from dynamic tuples
• Add an explicit argument [Tail[Tup]] because tail (on a Tuple6) was failing even on master
• Refactor direct usages of throw QuoteError

depends on #6210, checked with stageIt = true that it passes and reverted it back to false

[biboudis]

Rebased

Note to self: an assertion error occurs after erasure when compiling tests/run/tuple-cons-2.scala.
It seems the following synthesised code raises an error:

.asInstanceOf[{
  type evidence$22$_~$15 = Int
  type evidence$21$_~$5 = (Int, Int)(Tuple_this)(Tuple_this)
  evidence$22$_~$15 *: evidence$21$_~$5
}]

instead it should have been (Int, Int, Int)

[nicolasstucki]

We should move this to scala.internal

[biboudis]

I tried the change and I get an expected error 🤷‍♂️:

[info] Compiling 5 Scala sources to /Users/bibou/Projects/dotty/library/../out/bootstrap/dotty-library-bootstrapped/scala-0.14/classes ...
[error] -- Error: /Users/bibou/Projects/dotty/library/src-bootstrapped/scala/Tuple.scala:350:24 
[error] 350 |    if (Tuple.stageIt) (x.head, x.tail)
[error]     |                        ^^^^^^
[error]     |Could not find class scala.internal.StagedTuple$ in classpath. The most common reason for that is that you apply macros in the compilation run that defines them
[error]     | This location is in code that was inlined at Tuple.scala:224
[error]     | This location is in code that was inlined at Tuple.scala:350
[error] -- Error: /Users/bibou/Projects/dotty/library/src-bootstrapped/scala/internal/quoted/Matcher.scala:287:44 
[error] 287 |      case (Some(acc), Some(holes)) => Some(acc ++ holes)
[error]     |                                            ^^^^^^^^^^^^
[error]     |Could not find class scala.internal.StagedTuple$ in classpath. The most common reason for that is that you apply macros in the compilation run that defines them
[error]     | This location is in code that was inlined at Tuple.scala:66
[error]     | This location is in code that was inlined at Matcher.scala:287
[error] two errors found
[error] (dotty-library-bootstrapped / Compile / compileIncremental) Compilation failed
[error] Total time: 2 s, completed Apr 9, 2019 10:15:43 AM

Addressed

[biboudis]

Can I merge this @nicolasstucki ?