Presentation compiler reports incorrect error

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This test demonstrates how the Presentation Compiler can end up in a stale
state. In a nutshell, by loading and typechecking first A.scala, and then
B.scala, the following compilation error is reported in B compilation unit:

not enough arguments for constructor C: (key: String, componentStates: String)c.C

The default arguments in C (and potentially also the implicit conversion in A) seem to be playing a part.

The code for testing this problem is currently sitting in my own fork:

https://github.com/dotta/scala/tree/topic/presentation-compiler-reports-wrong-error

Let me know if I should open a pull-request against master right away, or wait until a fix is ready (though, the fix and the test code should ideally be part of the same pull request in the end).

We also have a related ticket in the Scala IDE issue tracker: http://scala-ide-portfolio.assembla.com/spaces/scala-ide/support/tickets/1000976.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-5975?orig=1
Reporter: @dotta
Affected Versions: 2.9.2, 2.10.0
Other Milestones: 2.10.0

[scabug]

@lrytz said:
fixed in [https://github.com/scala/scala/commit/70503355299263f95a3447701bb483375bf46665]