Optimize top level class searching in LazyJavaPackageScope

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

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/JavaClassFinder.java

@@ -18,15 +18,22 @@ package org.jetbrains.kotlin.load.java;
 
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.ReadOnly;
 import org.jetbrains.kotlin.load.java.structure.JavaClass;
 import org.jetbrains.kotlin.load.java.structure.JavaPackage;
 import org.jetbrains.kotlin.name.ClassId;
 import org.jetbrains.kotlin.name.FqName;
 
+import java.util.Set;
+
 public interface JavaClassFinder {
     @Nullable
     JavaClass findClass(@NotNull ClassId classId);
 
     @Nullable
     JavaPackage findPackage(@NotNull FqName fqName);
+
+    @ReadOnly
+    @Nullable
+    Set<String> knownClassNamesInPackage(@NotNull FqName packageFqName);
 }

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaPackageScope.kt

@@ -30,6 +30,7 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
+import org.jetbrains.kotlin.storage.NullableLazyValue
 import org.jetbrains.kotlin.storage.getValue
 
 class LazyJavaPackageScope(
@@ -38,6 +39,12 @@ class LazyJavaPackageScope(
         override val ownerDescriptor: LazyJavaPackageFragment
 ) : LazyJavaStaticScope(c) {
 
+    // Null means that it's impossible to determine list of class names in package, i.e. in IDE where special finders exist
+    // But for compiler though we can determine full list of class names by getting all class-file names in classpath and sources
+    private val knownClassNamesInPackage: NullableLazyValue<Set<String>> = c.storageManager.createNullableLazyValue {
+        c.components.finder.knownClassNamesInPackage(ownerDescriptor.fqName)
+    }
+
     private val partToFacade = c.storageManager.createLazyValue {
         val result = hashMapOf<String, String>()
         kotlinClasses@for (kotlinClass in ownerDescriptor.kotlinBinaryClasses) {
@@ -88,6 +95,12 @@ class LazyJavaPackageScope(
         if (!SpecialNames.isSafeIdentifier(name)) return null
 
         recordLookup(name, location)
+
+        val knownClassNamesInPackage = knownClassNamesInPackage()
+        if (knownClassNamesInPackage != null && name.asString() !in knownClassNamesInPackage) {
+            return null
+        }
+
         return classes(name)
     }
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/kotlin/KotlinClassFinder.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.load.kotlin
 
 import org.jetbrains.kotlin.load.java.structure.JavaClass
 import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.name.FqName
 
 interface KotlinClassFinder {
     fun findKotlinClass(classId: ClassId): KotlinJvmBinaryClass?