Fix reflection class lookup in default package

Do not append "." to the name of the class in the default package.

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java

@@ -41679,6 +41679,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
                     runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayKClass.kt");
                 }
 
+                @Test
+                @TestMetadata("arrayTypeInDefaultPackage.kt")
+                public void testArrayTypeInDefaultPackage() throws Exception {
+                    runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayTypeInDefaultPackage.kt");
+                }
+
                 @Test
                 @TestMetadata("classLiteralWithExpectedType.kt")
                 public void testClassLiteralWithExpectedType() throws Exception {

compiler/testData/codegen/box/reflection/annotations/onTypes/arrayTypeInDefaultPackage.kt

@@ -0,0 +1,20 @@
+// TARGET_BACKEND: JVM
+// WITH_REFLECT
+
+import kotlin.reflect.KClass
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+annotation class Nested(val value: String)
+
+@Target(AnnotationTarget.TYPE)
+annotation class Anno(
+    val aa: Array<Nested>,
+)
+
+fun f(): @Anno([Nested("OK")]) Unit {}
+
+fun box(): String {
+    val anno = ::f.returnType.annotations.single() as Anno
+    return anno.aa[0].value
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/BlackBoxCodegenTestGenerated.java

@@ -40245,6 +40245,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                     runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayKClass.kt");
                 }
 
+                @Test
+                @TestMetadata("arrayTypeInDefaultPackage.kt")
+                public void testArrayTypeInDefaultPackage() throws Exception {
+                    runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayTypeInDefaultPackage.kt");
+                }
+
                 @Test
                 @TestMetadata("classLiteralWithExpectedType.kt")
                 public void testClassLiteralWithExpectedType() throws Exception {

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java

@@ -41679,6 +41679,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                     runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayKClass.kt");
                 }
 
+                @Test
+                @TestMetadata("arrayTypeInDefaultPackage.kt")
+                public void testArrayTypeInDefaultPackage() throws Exception {
+                    runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayTypeInDefaultPackage.kt");
+                }
+
                 @Test
                 @TestMetadata("classLiteralWithExpectedType.kt")
                 public void testClassLiteralWithExpectedType() throws Exception {

compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -32100,6 +32100,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                     runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayKClass.kt");
                 }
 
+                @TestMetadata("arrayTypeInDefaultPackage.kt")
+                public void testArrayTypeInDefaultPackage() throws Exception {
+                    runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/arrayTypeInDefaultPackage.kt");
+                }
+
                 @TestMetadata("classLiteralWithExpectedType.kt")
                 public void testClassLiteralWithExpectedType() throws Exception {
                     runTest("compiler/testData/codegen/box/reflection/annotations/onTypes/classLiteralWithExpectedType.kt");

core/reflection.jvm/src/kotlin/reflect/jvm/internal/util.kt

@@ -97,9 +97,20 @@ private fun loadClass(classLoader: ClassLoader, packageName: String, className:
         }
     }
 
-    var fqName = "$packageName.${className.replace('.', '$')}"
-    if (arrayDimensions > 0) {
-        fqName = "[".repeat(arrayDimensions) + "L$fqName;"
+    val fqName = buildString {
+        if (arrayDimensions > 0) {
+            repeat(arrayDimensions) {
+                append("[")
+            }
+            append("L")
+        }
+        if (packageName.isNotEmpty()) {
+            append("$packageName.")
+        }
+        append(className.replace('.', '$'))
+        if (arrayDimensions > 0) {
+            append(";")
+        }
     }
 
     return classLoader.tryLoadClass(fqName)