SI-9268 Be robust against absent classfiles during signature parsing

When parsing a Java generic signature that references an inner
class `A$B`, we were tripping an assertion if the enclosing class
`A` was absent.

This commit creates a stub symbol for `B` when this happens, rather
than continuing on with `NoSymbol`.

The enclosed test shows that we can instantiate a class containing
a method referring to such an inner class with only a warning
about the absent classfile, and that an error is issued only upon
a subsequent attempt to call the method.

1 files changed, 3 insertions, 7 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index 994bcd8359..a59b9d3f48 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -1141,16 +1141,12 @@ abstract class ClassfileParser {
     private def innerSymbol(entry: InnerClassEntry): Symbol = {
       val name      = entry.originalName.toTypeName
       val enclosing = entry.enclosing
-      def getMember = (
+      val member = (
         if (enclosing == clazz) entry.scope lookup name
         else lookupMemberAtTyperPhaseIfPossible(enclosing, name)
       )
-      getMember
-      /*  There used to be an assertion that this result is not NoSymbol; changing it to an error
-       *  revealed it had been going off all the time, but has been swallowed by a catch t: Throwable
-       *  in Repository.scala. Since it has been accomplishing nothing except misleading anyone who
-       *  thought it wasn't triggering, I removed it entirely.
-       */
+      def newStub = enclosing.newStubSymbol(name, s"Unable to locate class corresponding to inner class entry for $name in owner ${entry.outerName}")
+      member.orElse(newStub)
     }
   }