[minor] Add the test confirming the wrong behavior of KT-48355

plugins/scripting/scripting-ide-services-test/test/org/jetbrains/kotlin/scripting/ide_services/ReplCompletionAndErrorsAnalysisTest.kt

@@ -509,6 +509,41 @@ class ReplCompletionAndErrorsAnalysisTest : TestCase() {
         }
     }
 
+    @Test
+    fun testRequiresOptIn() = test {
+        // This test confirms the wrong behavior described in KT-48355
+
+        // This compilation is here to initialize the compiler without RequiresOptIn option.
+        // If you remove it, warning disappears.
+        run {
+            code = "1"
+            doCompile
+        }
+
+        run {
+            code = """
+                import kotlin.time.*
+                @OptIn(ExperimentalTime::class)
+                val mark = TimeSource.Monotonic.markNow()
+            """.trimIndent()
+
+            compilationConfiguration = ScriptCompilationConfiguration {
+                compilerOptions("-Xopt-in=kotlin.RequiresOptIn")
+            }
+
+            doErrorCheck
+
+            expect {
+                // This warning is a wrong behavior, it should pass away after fixing KT-48355
+                addError(
+                    2, 2, 2, 7,
+                    "This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'",
+                    "WARNING"
+                )
+            }
+        }
+    }
+
     private val setupDefaultImportsCompletionRun: TestRunConfigurator = {
         compilationConfiguration = ScriptCompilationConfiguration {
             defaultImports(listOf("kotlin.math.atan"))