[test] Allow files with same names in tests

Introduce a directive that allows compiling different files with
matching names in tests.

compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/directives/ModuleStructureDirectives.kt

@@ -39,6 +39,12 @@ object ModuleStructureDirectives : SimpleDirectivesContainer() {
         """.trimIndent()
     )
 
+    val ALLOW_FILES_WITH_SAME_NAMES by directive(
+        """
+        Allows specifying test files with the same names using the // FILE directive.
+        """.trimIndent()
+    )
+
     val TARGET_FRONTEND by stringDirective(
         """
             Usage: // TARGET_FRONTEND: {Frontend}

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/impl/ModuleStructureExtractorImpl.kt

@@ -100,6 +100,8 @@ class ModuleStructureExtractorImpl(
         private var linesOfCurrentFile = mutableListOf<String>()
         private var endLineNumberOfLastFile = -1
 
+        private var allowFilesWithSameNames = false
+
         private var directivesBuilder = RegisteredDirectivesParser(directivesContainer, assertions)
         private var moduleDirectivesBuilder: RegisteredDirectivesParser = directivesBuilder
         private var fileDirectivesBuilder: RegisteredDirectivesParser? = null
@@ -218,6 +220,9 @@ class ModuleStructureExtractorImpl(
                     }
                     currentFileName = (values.first() as String).also(::validateFileName)
                 }
+                ModuleStructureDirectives.ALLOW_FILES_WITH_SAME_NAMES -> {
+                    allowFilesWithSameNames = true
+                }
                 ModuleStructureDirectives.TARGET_PLATFORM -> {
                     if (currentModuleTargetPlatform != null) {
                         assertions.fail { "Target platform already specified twice for module $currentModuleName" }
@@ -367,7 +372,7 @@ class ModuleStructureExtractorImpl(
                 "module_${currentModuleName}_$defaultFileName"
             }
             val filename = currentFileName ?: actualDefaultFileName
-            if (filesOfCurrentModule.any { it.name == filename }) {
+            if (!allowFilesWithSameNames && filesOfCurrentModule.any { it.name == filename }) {
                 error("File with name \"$filename\" already defined in module ${currentModuleName ?: actualDefaultFileName}")
             }
             val directives = fileDirectivesBuilder?.build()?.also { directives ->
@@ -419,6 +424,7 @@ class ModuleStructureExtractorImpl(
                 moduleDirectivesBuilder = directivesBuilder
             }
             currentFileName = null
+            allowFilesWithSameNames = false
             resetDirectivesBuilder()
             fileDirectivesBuilder = directivesBuilder
         }