SI-6440 Address regressions around MissingRequirementError

 Go back to using globalError to report when a stub's info is referenced,
 and only throw the MissingRequirementError when compilation really
 must abort due to having a StubTermSymbol in a place where a
 StubClassSymbol would have been a better choice.

 This situation arises when an entire package is missing from the
 classpath, as was the case in the reported bug.

 Adds `StoreReporterDirectTest`, which buffers messages issued
 during compilation for more structured interrogation. Use this
 in two test for manifests -- these tests were using a crude means
 of grepping compiler console output to focus on the relevant output,
 but this approach was insufficient with the new multi-line error
 message emitted as part of this change.

 Also used that base test class to add two new tests: one for
 the reported error (package missing), and another for a simpler
 error (class missing). The latter test shows how stub symbols
 allow code to compile if it doesn't the subset of signatures
 in some type that refer to a missing class.

 Gave the INFO/WARNING/ERROR members of Reporter sensible
 toString implementations; they inherit from Enumeration#Value
 in an unusual manner (why?) that means the built in toString of
 Enumeration printed `Severity@0`.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/reflect/scala/reflect/internal/pickling/UnPickler.scala b/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
index 5464a68205..f3a5053a91 100644
--- a/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
+++ b/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
@@ -234,10 +234,10 @@ abstract class UnPickler {
               adjust(mirrorThatLoaded(owner).missingHook(owner, name)) orElse {
                 // (5) Create a stub symbol to defer hard failure a little longer.
                 val missingMessage =
-                  s"""|A signature in $filename refers to ${name.longString} in ${owner.fullLocationString}
-                      |which is not available. It may be completely missing from the current classpath,
-                      |or the version on the classpath might be incompatible with the version used when
-                      |compiling $filename.""".stripMargin
+                  s"""|bad symbolic reference. A signature in $filename refers to ${name.longString}
+                      |in ${owner.kindString} ${owner.fullName} which is not available.
+                      |It may be completely missing from the current classpath, or the version on
+                      |the classpath might be incompatible with the version used when compiling $filename.""".stripMargin
                 owner.newStubSymbol(name, missingMessage)
               }
             }