Move: Fix name lengthening when moving from default package

#KT-10696 Fixed

idea/src/org/jetbrains/kotlin/idea/refactoring/move/moveUtils.kt

@@ -22,7 +22,6 @@ import com.intellij.openapi.ui.DialogWrapper
 import com.intellij.openapi.util.Comparing
 import com.intellij.openapi.util.Key
 import com.intellij.psi.*
-import com.intellij.psi.util.PsiTreeUtil
 import com.intellij.refactoring.RefactoringBundle
 import com.intellij.refactoring.RefactoringSettings
 import com.intellij.refactoring.copy.CopyFilesOrDirectoriesHandler
@@ -183,7 +182,12 @@ fun KtElement.lazilyProcessInternalReferencesToUpdateOnPackageNameChange(
                 return fqName.asString().let {
                     val prefix = containerFqName.asString()
                     val prefixOffset = it.indexOf(prefix)
-                    val newFqName = FqName(it.replaceRange(prefixOffset..prefixOffset + prefix.length - 1, newContainer.fqName!!.asString()))
+                    val newFqName = if (prefix.isEmpty()) {
+                        FqName("${newContainer.fqName!!.asString()}.$it")
+                    }
+                    else {
+                        FqName(it.replaceRange(prefixOffset..prefixOffset + prefix.length - 1, newContainer.fqName!!.asString()))
+                    }
                     MoveRenameSelfUsageInfo(refExpr.mainReference, declaration, newFqName)
                 }
             }

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/moveFromDefaultPackage/after/target/Extra.kt

@@ -0,0 +1,8 @@
+package target
+
+class Extra {
+    fun use() {
+        val v = Extra().Intro()
+    }
+    inner class Intro {}
+}

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/moveFromDefaultPackage/after/test.kt

@@ -0,0 +1,3 @@
+class X {
+
+}

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/moveFromDefaultPackage/before/test.kt

@@ -0,0 +1,10 @@
+class <caret>Extra {
+    fun use() {
+        val v = Extra().Intro()
+    }
+    inner class Intro {}
+}
+
+class X {
+
+}

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/moveFromDefaultPackage/moveFromDefaultPackage.test

@@ -0,0 +1,6 @@
+{
+  "mainFile": "test.kt",
+  "type": "MOVE_KOTLIN_TOP_LEVEL_DECLARATIONS",
+  "targetPackage": "target",
+  "withRuntime": "true"
+}

idea/tests/org/jetbrains/kotlin/idea/refactoring/move/MoveTestGenerated.java

@@ -419,6 +419,12 @@ public class MoveTestGenerated extends AbstractMoveTest {
         doTest(fileName);
     }
 
+    @TestMetadata("kotlin/moveTopLevelDeclarations/misc/moveFromDefaultPackage/moveFromDefaultPackage.test")
+    public void testKotlin_moveTopLevelDeclarations_misc_moveFromDefaultPackage_MoveFromDefaultPackage() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/moveFromDefaultPackage/moveFromDefaultPackage.test");
+        doTest(fileName);
+    }
+
     @TestMetadata("kotlin/moveTopLevelDeclarations/misc/moveFunctionWithImportsRetained/moveFunctionWithImportsRetained.test")
     public void testKotlin_moveTopLevelDeclarations_misc_moveFunctionWithImportsRetained_MoveFunctionWithImportsRetained() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/moveFunctionWithImportsRetained/moveFunctionWithImportsRetained.test");