[const-val] fix const val compiler error (#1085)

Author: sk1418

core-kotlin-modules/core-kotlin-lang-5/src/test/kotlin/com/baeldung/constValCompilerError/ConstValCompilerErrorUnitTest.kt

@@ -0,0 +1,54 @@
+package com.baeldung.constValCompilerError
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+const val MSG_PREFIX_TOP_LVL: String = "App User Event (top level):"
+
+object AppConstants {
+    const val MSG_PREFIX: String = "App User Event (in object):"
+}
+
+data class UserEvent(val name: String) {
+    // ===== code doesn't compile =====
+    // const val MSG_PREFIX: String = "App User Event:"
+    // fun login(): String {
+    //     return "$MSG_PREFIX User [$name] login successful"
+    // }
+    // ================================
+
+    fun loginTopLevelPrefix(): String {
+        return "$MSG_PREFIX_TOP_LVL User [$name] login successful"
+    }
+
+    fun loginObjectPrefix(): String {
+        return "${AppConstants.MSG_PREFIX} User [$name] login successful"
+    }
+
+    fun loginCompanionObjPrefix(): String {
+        return "$MSG_PREFIX_IN_COMPANION_OBJ User [$name] login successful"
+    }
+
+    companion object {
+        const val MSG_PREFIX_IN_COMPANION_OBJ: String = "App User Event (in Companion object):"
+    }
+}
+
+class ConstValCompilerErrorUnitTest {
+    @Test
+    fun `when using top level constant then correct`() {
+        val result = UserEvent("Kai").loginTopLevelPrefix()
+        assertEquals("App User Event (top level): User [Kai] login successful", result)
+    }
+
+    @Test
+    fun `when using constant in object then correct`() {
+        val result = UserEvent("Kai").loginObjectPrefix()
+        assertEquals("App User Event (in object): User [Kai] login successful", result)
+    }
+    @Test
+    fun `when using constant in companion object then correct`() {
+        val result = UserEvent("Kai").loginCompanionObjPrefix()
+        assertEquals("App User Event (in Companion object): User [Kai] login successful", result)
+    }
+}