Optimize top level class searching in LazyJavaPackageScope

Do not try to search something, that is known not to exist

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/JvmDependenciesIndex.kt

@@ -20,9 +20,7 @@ import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.util.containers.IntArrayList
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
-import java.util.ArrayList
-import java.util.EnumSet
-import java.util.HashMap
+import java.util.*
 
 data class JavaRoot(val file: VirtualFile, val type: JavaRoot.RootType, val prefixFqName: FqName? = null) {
     enum class RootType {
@@ -99,6 +97,24 @@ class JvmDependenciesIndex(_roots: List<JavaRoot>) {
         }
     }
 
+    fun collectKnownClassNamesInPackage(
+            packageFqName: FqName
+    ): Set<String> {
+        var result = hashSetOf<String>()
+        traverseDirectoriesInPackage(packageFqName, continueSearch = {
+            dir, rootType ->
+
+            for (child in dir.children) {
+                if (child.extension != "class" && child.extension != "java") continue
+                result.add(child.nameWithoutExtension)
+            }
+
+            true
+        })
+
+        return result
+    }
+
     private data class HandleResult<T : Any>(val result: T?, val continueSearch: Boolean)
 
     private fun <T : Any> search(

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/KotlinCliJavaFileManagerImpl.kt

@@ -120,6 +120,8 @@ class KotlinCliJavaFileManagerImpl(private val myPsiManager: PsiManager)
         return findClassInPsiFile(classNameWithInnerClasses, file)
     }
 
+    override fun knownClassNamesInPackage(packageFqName: FqName) = index.collectKnownClassNamesInPackage(packageFqName)
+
     companion object {
         private val LOG = Logger.getInstance(KotlinCliJavaFileManagerImpl::class.java)