Partially fix Java interop for emitted inner classes

The backend uses `rawname` to define the "inner name" of an InnerClass
entry in a classfile, this should be the simple name of the class before
any mangling takes place.

Fixing this allows Java code to reference dotty inner classes, except if
they're defined in objects which is still broken until
lampepfl/scala#4 is merged and a new backend
is published.

Author: smarter

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -560,7 +560,10 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
     def javaBinaryName: Name = toDenot(sym).fullNameSeparated("/") // addModuleSuffix(fullNameInternal('/'))
     def javaClassName: String = toDenot(sym).fullName.toString// addModuleSuffix(fullNameInternal('.')).toString
     def name: Name = sym.name
-    def rawname: Name = sym.name // todo ????
+    def rawname: Name = {
+      val original = toDenot(sym).initial
+      sym.name(ctx.withPhase(original.validFor.phaseId))
+    }
 
     // types
     def info: Type = toDenot(sym).info

tests/pos-java-interop/innerClass/Outer.scala

@@ -0,0 +1,8 @@
+class Outer {
+  class InnerInClass
+
+  def inner() = new InnerInClass
+}
+object Outer {
+  class InnerInObject
+}

tests/pos-java-interop/innerClass/Test.java

@@ -0,0 +1,9 @@
+public class Test {
+  public static void test() {
+    Outer outer = new Outer();
+    Outer.InnerInClass innerInClass = outer.inner();
+
+    // Does not work yet, requires https://github.com/DarkDimius/scala/pull/4
+    // Outer.InnerInObject innerInObject = new Outer.InnerInObject();
+  }
+}