From fb296b5b95a56fe380bdbe7c9f61d092bd21f275 Mon Sep 17 00:00:00 2001
From: Alexander Udalov <alexander.udalov@jetbrains.com>
Date: Wed, 3 Feb 2021 21:21:55 +0100
Subject: [PATCH] Do not create Array instance in kotlin-reflect where not
 necessary

Although the previous code of computing JVM internal name from a Class
instance was shorter, it led to unnecessary creation of array types,
which is less performant and makes configuration of kotlin-reflect for
GraalVM native-image more verbose.

Unfortunately I didn't succeed in writing a test for this, since
`Array.newInstance` calls a native method which doesn't record any trace
of it being called in the class loader: the resulting array type never
goes through findClass/loadClass, and is not visible via
findLoadedClass.

 #KT-44594 Fixed
---
 .../runtime/structure/reflectClassUtil.kt     | 23 ++++++++++++-------
 .../jvm/internal/KDeclarationContainerImpl.kt |  1 -
 .../kotlin/reflect/jvm/internal/KTypeImpl.kt  |  1 -
 .../src/kotlin/reflect/jvm/internal/util.kt   |  3 +++
 4 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/core/descriptors.runtime/src/org/jetbrains/kotlin/descriptors/runtime/structure/reflectClassUtil.kt b/core/descriptors.runtime/src/org/jetbrains/kotlin/descriptors/runtime/structure/reflectClassUtil.kt
index fba5e29b020..76eec25e191 100644
--- a/core/descriptors.runtime/src/org/jetbrains/kotlin/descriptors/runtime/structure/reflectClassUtil.kt
+++ b/core/descriptors.runtime/src/org/jetbrains/kotlin/descriptors/runtime/structure/reflectClassUtil.kt
@@ -67,16 +67,23 @@ val Class<*>.classId: ClassId
     }
 
 val Class<*>.desc: String
-    get() {
-        if (this == Void.TYPE) return "V"
-        // This is a clever exploitation of a format returned by Class.getName(): for arrays, it's almost an internal name,
-        // but with '.' instead of '/'
-        return createArrayType().name.substring(1).replace('.', '/')
+    get() = when {
+        isPrimitive -> when (name) {
+            "boolean" -> "Z"
+            "char" -> "C"
+            "byte" -> "B"
+            "short" -> "S"
+            "int" -> "I"
+            "float" -> "F"
+            "long" -> "J"
+            "double" -> "D"
+            "void" -> "V"
+            else -> throw IllegalArgumentException("Unsupported primitive type: $this")
+        }
+        isArray -> name.replace('.', '/')
+        else -> "L${name.replace('.', '/')};"
     }
 
-fun Class<*>.createArrayType(): Class<*> =
-    Array.newInstance(this, 0)::class.java
-
 /**
  * @return all arguments of a parameterized type, including those of outer classes in case this type represents an inner generic.
  * The returned list starts with the arguments to the innermost class, then continues with those of its outer class, and so on.
diff --git a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KDeclarationContainerImpl.kt b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KDeclarationContainerImpl.kt
index d83e7387884..35d14c74401 100644
--- a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KDeclarationContainerImpl.kt
+++ b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KDeclarationContainerImpl.kt
@@ -19,7 +19,6 @@ package kotlin.reflect.jvm.internal
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.runtime.components.RuntimeModuleData
 import org.jetbrains.kotlin.descriptors.runtime.components.tryLoadClass
-import org.jetbrains.kotlin.descriptors.runtime.structure.createArrayType
 import org.jetbrains.kotlin.descriptors.runtime.structure.safeClassLoader
 import org.jetbrains.kotlin.descriptors.runtime.structure.wrapperByPrimitive
 import org.jetbrains.kotlin.load.java.JvmAbi
diff --git a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KTypeImpl.kt b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KTypeImpl.kt
index 49666340603..5dd3fe793d4 100644
--- a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KTypeImpl.kt
+++ b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KTypeImpl.kt
@@ -19,7 +19,6 @@ package kotlin.reflect.jvm.internal
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.TypeAliasDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
-import org.jetbrains.kotlin.descriptors.runtime.structure.createArrayType
 import org.jetbrains.kotlin.descriptors.runtime.structure.parameterizedTypeArguments
 import org.jetbrains.kotlin.descriptors.runtime.structure.primitiveByWrapper
 import org.jetbrains.kotlin.types.KotlinType
diff --git a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/util.kt b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/util.kt
index cda72d58eb5..cf7dc541715 100644
--- a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/util.kt
+++ b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/util.kt
@@ -101,6 +101,9 @@ private fun loadClass(classLoader: ClassLoader, packageName: String, className:
     return classLoader.tryLoadClass(fqName)
 }
 
+internal fun Class<*>.createArrayType(): Class<*> =
+    java.lang.reflect.Array.newInstance(this, 0)::class.java
+
 internal fun DescriptorVisibility.toKVisibility(): KVisibility? =
     when (this) {
         DescriptorVisibilities.PUBLIC -> KVisibility.PUBLIC