Optimize class lookups in DeserializedPackageMemberScope

Do not try to load classes (and litter in ClassDeserializer#classes cache with
unsuccessful requests) which the deserialized scope knows nothing about. This
is possible because deserialized scopes have the full list of their class names

core/descriptors/src/org/jetbrains/kotlin/builtins/functions/BuiltInFictitiousFunctionClassFactory.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.serialization.deserialization.ClassDescriptorFactory
 import org.jetbrains.kotlin.storage.StorageManager
 
@@ -63,6 +64,12 @@ class BuiltInFictitiousFunctionClassFactory(
         }
     }
 
+    override fun shouldCreateClass(packageFqName: FqName, name: Name): Boolean {
+        val string = name.asString()
+        return (string.startsWith("Function") || string.startsWith("KFunction")) // an optimization
+               && parseClassName(string, packageFqName) != null
+    }
+
     override fun createClass(classId: ClassId): ClassDescriptor? {
         if (classId.isLocal || classId.isNestedClass) return null
 

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/ClassDescriptorFactory.kt

@@ -18,11 +18,17 @@ package org.jetbrains.kotlin.serialization.deserialization
 
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
 
 interface ClassDescriptorFactory {
+    fun shouldCreateClass(packageFqName: FqName, name: Name): Boolean
+
     fun createClass(classId: ClassId): ClassDescriptor?
 
     object EMPTY : ClassDescriptorFactory {
+        override fun shouldCreateClass(packageFqName: FqName, name: Name): Boolean = false
+
         override fun createClass(classId: ClassId): ClassDescriptor? = null
     }
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedClassDescriptor.kt

@@ -245,8 +245,10 @@ class DeserializedClassDescriptor(
             }
         }
 
-        override fun getClassDescriptor(name: Name): ClassifierDescriptor? =
-                classDescriptor.enumEntries?.findEnumEntry(name) ?: classDescriptor.nestedClasses?.findNestedClass(name)
+        override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor? {
+            recordLookup(name, location)
+            return classDescriptor.enumEntries?.findEnumEntry(name) ?: classDescriptor.nestedClasses?.findNestedClass(name)
+        }
 
         override fun addClassDescriptors(result: MutableCollection<DeclarationDescriptor>, nameFilter: (Name) -> Boolean) {
             result.addAll(classDescriptor.nestedClasses?.all().orEmpty())

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedMemberScope.kt

@@ -103,13 +103,6 @@ abstract class DeserializedMemberScope protected constructor(
         return properties.invoke(name)
     }
 
-    override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor? {
-        recordLookup(name, location)
-        return getClassDescriptor(name)
-    }
-
-    protected abstract fun getClassDescriptor(name: Name): ClassifierDescriptor?
-
     protected abstract fun addClassDescriptors(result: MutableCollection<DeclarationDescriptor>, nameFilter: (Name) -> Boolean)
 
     protected fun computeDescriptors(
@@ -185,7 +178,7 @@ abstract class DeserializedMemberScope protected constructor(
         p.println("}")
     }
 
-    private fun recordLookup(name: Name, from: LookupLocation) {
+    protected fun recordLookup(name: Name, from: LookupLocation) {
         c.components.lookupTracker.record(from, c.containingDeclaration, name)
     }
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedPackageMemberScope.kt

@@ -16,10 +16,7 @@
 
 package org.jetbrains.kotlin.serialization.deserialization.descriptors
 
-import org.jetbrains.kotlin.descriptors.ClassDescriptor
-import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
-import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor
-import org.jetbrains.kotlin.descriptors.SourceElement
+import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.incremental.components.LookupLocation
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.name.ClassId
@@ -51,9 +48,17 @@ open class DeserializedPackageMemberScope(
     override fun getContributedDescriptors(kindFilter: DescriptorKindFilter, nameFilter: (Name) -> Boolean)
             = computeDescriptors(kindFilter, nameFilter, NoLookupLocation.WHEN_GET_ALL_DESCRIPTORS)
 
-    override fun getClassDescriptor(name: Name): ClassDescriptor? =
-            if (SpecialNames.isSafeIdentifier(name)) c.components.deserializeClass(ClassId(packageFqName, name))
-            else null
+    override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor? {
+        if (SpecialNames.isSafeIdentifier(name) &&
+            (name in classNames || c.components.fictitiousClassDescriptorFactory.shouldCreateClass(packageFqName, name))) {
+            recordLookup(name, location)
+            return getClassDescriptor(name)
+        }
+        return null
+    }
+
+    private fun getClassDescriptor(name: Name): ClassDescriptor? =
+            c.components.deserializeClass(ClassId(packageFqName, name))
 
     override fun addClassDescriptors(result: MutableCollection<DeclarationDescriptor>, nameFilter: (Name) -> Boolean) {
         for (className in classNames) {