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.

3 files changed, 57 insertions, 0 deletions

diff --git a/test/files/run/t9268.check b/test/files/run/t9268.check
new file mode 100644
index 0000000000..90ef940eb3
--- /dev/null
+++ b/test/files/run/t9268.check
@@ -0,0 +1,5 @@
+Compiling Client1
+pos: NoPosition Class Waiter not found - continuing with a stub. WARNING
+Compiling Client2
+pos: NoPosition Class Waiter not found - continuing with a stub. WARNING
+pos: NoPosition Unable to locate class corresponding to inner class entry for Predicate in owner Waiter ERROR
diff --git a/test/files/run/t9268/Java.java b/test/files/run/t9268/Java.java
new file mode 100644
index 0000000000..c9a0bec3ff
--- /dev/null
+++ b/test/files/run/t9268/Java.java
@@ -0,0 +1,12 @@
+public class Java {
+}
+
+class Partial {
+	public <E extends java.lang.Exception> long waitFor(long l, Waiter.Predicate<E> pred) throws E {
+		return 0L;
+	}
+}
+
+class Waiter {
+	interface Predicate<E> {}
+}
diff --git a/test/files/run/t9268/Test.scala b/test/files/run/t9268/Test.scala
new file mode 100644
index 0000000000..813cbe7b60
--- /dev/null
+++ b/test/files/run/t9268/Test.scala
@@ -0,0 +1,40 @@
+import scala.tools.partest._
+import java.io.File
+
+object Test extends StoreReporterDirectTest {
+  def code = ???
+
+  def compileCode(code: String) = {
+    val classpath = List(sys.props("partest.lib"), testOutput.path) mkString sys.props("path.separator")
+    compileString(newCompiler("-cp", classpath, "-d", testOutput.path))(code)
+  }
+
+  def client1 = """
+    class Client1 { def p(p: Partial) = p.toString }
+  """
+
+  def client2 = """
+    class Client2 { def p(p: Partial) = p.waitFor() }
+  """
+
+  def deleteClass(s: String) = {
+    val f = new File(testOutput.path, s + ".class")
+    assert(f.exists)
+    f.delete()
+  }
+
+  def show(): Unit = {
+    deleteClass("Waiter")
+    deleteClass("Waiter$Predicate")
+
+    // Used to crash in Java Generic Signature parsing
+    println("Compiling Client1")
+    compileCode(client1)
+    println(storeReporter.infos.mkString("\n"))
+    storeReporter.reset()
+    println("Compiling Client2")
+    compileCode(client2)
+    println(storeReporter.infos.mkString("\n"))
+  }
+}
+