Allow building UAST for in-memory virtual files

compiler/light-classes/src/org/jetbrains/kotlin/asJava/classes/KtLightClassForSourceDeclaration.kt

@@ -104,8 +104,6 @@ abstract class KtLightClassForSourceDeclaration(protected val classOrObject: KtC
     }
 
     private val _containingFile: PsiFile by lazyPub {
-        classOrObject.containingFile.virtualFile ?: error("No virtual file for " + classOrObject.text)
-
         object : FakeFileForLightClass(
                 classOrObject.containingKtFile,
                 { if (classOrObject.isTopLevel()) this else create(getOutermostClassOrObject(classOrObject))!! },

compiler/light-classes/src/org/jetbrains/kotlin/asJava/elements/FakeFileForLightClass.kt

@@ -33,7 +33,7 @@ open class FakeFileForLightClass(
         private val lightClass: () -> KtLightClass,
         private val stub: () -> PsiClassHolderFileStub<*>,
         private val packageFqName: FqName = ktFile.packageFqName
-) : ClsFileImpl(ClassFileViewProvider(ktFile.manager, ktFile.virtualFile)) {
+) : ClsFileImpl(ClassFileViewProvider(ktFile.manager, ktFile.viewProvider.virtualFile)) {
     override fun getPackageName() = packageFqName.asString()
 
     override fun getStub() = stub()