Move reporting logic into Reporting trait

Move code from Global/SymbolTable to separate Reporting traits to
start carving out an interface in scala.reflect.internal.Reporting,
with internals in scala.tools.nsc. Reporting is mixed into the cake.
It contains a nested class PerRunReporting.

Should do the same for debugging/logging.

The idea is that CompilationUnit and Global forward all reporting
to Reporter. The Reporting trait contains these forwarders, and
PerRunReporting, which accumulates warning state during a run.

In the process, I slightly changed the behavior of `globalError`
in reflect.internal.SymbolTable: it used to abort, weirdly.
I assume that was dummy behavior to avoid introducing an abstract method.
It's immediately overridden in Global, and I couldn't find any other subclasses,
so I don't think the behavior in SymbolTable was ever observed.

Provide necessary hooks for scala.reflect.macros.Parsers#parse.
See scala/reflect/macros/contexts/Parsers.scala's parse method,
which overrides the reporter to detect when parsing goes wrong.
This should be refactored, but that goes beyond the scope of this PR.

Don't pop empty macro context stack.
(Ran into this while reworking -Xfatal-warnings logic.)

Fix -Xfatal-warnings behavior (and check files): it wasn't meant to
influence warning reporting, except for emitting one final error;
if necessary to fail the compile (when warnings but no errors were reported).
Warnings should stay warnings.

This was refactored in fbbbb22946, but we soon seem to have relapsed.
An hour of gitfu did not lead to where it went wrong. Must've been a merge.

6 files changed, 18 insertions, 14 deletions

diff --git a/test/files/neg/checksensible.check b/test/files/neg/checksensible.check
index 38cc5ec447..1b53fa5fb9 100644
--- a/test/files/neg/checksensible.check
+++ b/test/files/neg/checksensible.check
@@ -97,7 +97,7 @@ checksensible.scala:84: warning: comparing values of types EqEqRefTest.this.C3 a
 checksensible.scala:95: warning: comparing values of types Unit and Int using `!=' will always yield true
     while ((c = in.read) != -1)
                          ^
+warning: there were 3 deprecation warnings; re-run with -deprecation for details
 error: No warnings can be incurred under -Xfatal-warnings.
-error: there were 3 deprecation warnings; re-run with -deprecation for details
-33 warnings found
-two errors found
+34 warnings found
+one error found
diff --git a/test/files/neg/overloaded-implicit.check b/test/files/neg/overloaded-implicit.check
index d9594d126a..5cf6ac528b 100644
--- a/test/files/neg/overloaded-implicit.check
+++ b/test/files/neg/overloaded-implicit.check
@@ -4,7 +4,7 @@ overloaded-implicit.scala:2: warning: parameterized overloaded implicit methods
 overloaded-implicit.scala:3: warning: parameterized overloaded implicit methods are not visible as view bounds
   implicit def imp1[T](x: Set[T]): Map[T, T] = Map()
                ^
+warning: there were 4 feature warnings; re-run with -feature for details
 error: No warnings can be incurred under -Xfatal-warnings.
-error: there were 4 feature warnings; re-run with -feature for details
-two warnings found
-two errors found
+three warnings found
+one error found
diff --git a/test/files/neg/t1909-object.check b/test/files/neg/t1909-object.check
index 401c1f7ebf..7141c84d4b 100644
--- a/test/files/neg/t1909-object.check
+++ b/test/files/neg/t1909-object.check
@@ -1,4 +1,6 @@
-t1909-object.scala:4: error: !!! SI-1909 Unable to STATICally lift object InnerTrouble$1, which is defined in the self- or super-constructor call of class Kaboom. A VerifyError is likely.
+t1909-object.scala:4: warning: !!! SI-1909 Unable to STATICally lift object InnerTrouble$1, which is defined in the self- or super-constructor call of class Kaboom. A VerifyError is likely.
       object InnerTrouble
              ^
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
 one error found
diff --git a/test/files/neg/t5675.check b/test/files/neg/t5675.check
index 13226935dc..3b3b2fa04c 100644
--- a/test/files/neg/t5675.check
+++ b/test/files/neg/t5675.check
@@ -1,2 +1,4 @@
-error: there was one feature warning; re-run with -feature for details
+warning: there was one feature warning; re-run with -feature for details
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
 one error found
diff --git a/test/files/neg/t6567.check b/test/files/neg/t6567.check
index 3243fde0cd..f42f157371 100644
--- a/test/files/neg/t6567.check
+++ b/test/files/neg/t6567.check
@@ -4,7 +4,7 @@ t6567.scala:8: warning: Suspicious application of an implicit view (Test.this.a2
 t6567.scala:10: warning: Suspicious application of an implicit view (Test.this.a2b) in the argument to Option.apply.
   val b: Option[B] = Option(a)
                            ^
+warning: there was one feature warning; re-run with -feature for details
 error: No warnings can be incurred under -Xfatal-warnings.
-error: there was one feature warning; re-run with -feature for details
-two warnings found
-two errors found
+three warnings found
+one error found
diff --git a/test/files/neg/unchecked-refinement.check b/test/files/neg/unchecked-refinement.check
index b49e47fcbb..0bb944621b 100644
--- a/test/files/neg/unchecked-refinement.check
+++ b/test/files/neg/unchecked-refinement.check
@@ -10,7 +10,7 @@ unchecked-refinement.scala:23: warning: a pattern match on a refinement type is
 unchecked-refinement.scala:24: warning: a pattern match on a refinement type is unchecked
     /* nowarn - todo */ case x: AnyRef { def size: Int } if b  => x.size   // this could/should do a static conformance test and not warn
                                 ^
+warning: there was one feature warning; re-run with -feature for details
 error: No warnings can be incurred under -Xfatal-warnings.
-error: there was one feature warning; re-run with -feature for details
-four warnings found
-two errors found
+5 warnings found
+one error found