Unclutter Reporter. Move truncation to ReplReporter.

Refactor to reduce the Reporter interface. Working towards
minimal interfaces in scala.reflect.internal that can be consumed by sbt/IDE/....
The scala.tools.nsc package is entirely private to the compiler (in principle).

A `Reporter` should only be used to inform (info/warning/error). No state.
Ideally, we'd move to having only one reporter, whose lifetime is adjusted
appropriately (from per-run in general to per-context for type checking,
so errors can be buffered -- "silenced" -- during nested type checking calls).

Start the clean up by moving truncation to the REPL,
since it's not relevant for regular reporting. Perversely, we were checking
truncation all the time, even though it's only on during a repl run.
(Truncation is now always turned off in the repl under -verbose.)

Untangle error resetting on symbols from error reporting (reportAdditionalErrors).
This fixes a nice&subtle bug that caused feature warnings to be suppressed under
`-Xfatal-warnings`:

```
def reportCompileErrors() {
  if (!reporter.hasErrors && reporter.hasWarnings && settings.fatalWarnings)
    globalError("No warnings can be incurred under -Xfatal-warnings.")

  if (reporter.hasErrors) { ... }
  else {
    // will erroneously not get here if
    // `reporter.hasWarnings && settings.fatalWarnings`
    // since the `globalError` call above means `reporter.hasErrors`...
    allConditionalWarnings foreach (_.summarize())
    ...
  }
}
```

The second `if`'s condition depends on the `globalError` call in the first `if`...

1 files changed, 19 insertions, 0 deletions

diff --git a/src/repl/scala/tools/nsc/interpreter/ReplReporter.scala b/src/repl/scala/tools/nsc/interpreter/ReplReporter.scala
index b20166d070..88372334d6 100644
--- a/src/repl/scala/tools/nsc/interpreter/ReplReporter.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ReplReporter.scala
@@ -9,11 +9,29 @@ package interpreter
 import reporters._
 import IMain._
 
+import scala.reflect.internal.util.Position
+
 /** Like ReplGlobal, a layer for ensuring extra functionality.
  */
 class ReplReporter(intp: IMain) extends ConsoleReporter(intp.settings, Console.in, new ReplStrippingWriter(intp)) {
   def printUntruncatedMessage(msg: String) = withoutTruncating(printMessage(msg))
 
+  /** Whether very long lines can be truncated.  This exists so important
+   *  debugging information (like printing the classpath) is not rendered
+   *  invisible due to the max message length.
+   */
+  private var _truncationOK: Boolean = !intp.settings.verbose
+  def truncationOK = _truncationOK
+  def withoutTruncating[T](body: => T): T = {
+    val saved = _truncationOK
+    _truncationOK = false
+    try body
+    finally _truncationOK = saved
+  }
+
+  override def warning(pos: Position, msg: String): Unit = withoutTruncating(super.warning(pos, msg))
+  override def error(pos: Position, msg: String): Unit   = withoutTruncating(super.error(pos, msg))
+
   override def printMessage(msg: String) {
     // Avoiding deadlock if the compiler starts logging before
     // the lazy val is complete.
@@ -31,4 +49,5 @@ class ReplReporter(intp: IMain) extends ConsoleReporter(intp.settings, Console.i
     if (intp.totalSilence) ()
     else super.displayPrompt()
   }
+
 }