KT-64932: add support for no-package top level functions

Merge-request: KT-MR-13879
Merged-by: Artem Olkov <artem.olkov@jetbrains.com>

plugins/swift-export/swift-export.backend/src/org/jetbrains/kotlin/swiftexport/SwiftExportExtension.kt

@@ -166,9 +166,14 @@ class SwiftExportExtension(
             override fun visitFunction(function: SirFunction) {
                 val fqName = (function.origin as? SirKotlinOrigin.Function)?.fqName
                     ?: return
+                val fqNameForBridge = if (fqName.count() == 1) {
+                    listOf("__root__", fqName.first()) // todo: should be changed with correct mangling KT-64970
+                } else {
+                    fqName
+                }
                 val bridgeRequest = BridgeRequest(
                     function,
-                    fqName.joinToString("_"),
+                    fqNameForBridge.joinToString("_"),
                     fqName
                 )
                 requests += bridgeRequest

plugins/swift-export/testData/no_package.golden.h

@@ -0,0 +1,3 @@
+#include <stdint.h>
+
+int32_t __root___meaningOfLife();

plugins/swift-export/testData/no_package.golden.kt

@@ -0,0 +1,7 @@
+import kotlin.native.internal.ExportedBridge
+
+@ExportedBridge("__root___meaningOfLife")
+public fun __root___meaningOfLife(): Int {
+    val result = meaningOfLife()
+    return result
+}

plugins/swift-export/testData/no_package.golden.swift

@@ -0,0 +1,3 @@
+public func meaningOfLife() -> Swift.Int32 {
+    return __root___meaningOfLife()
+}

plugins/swift-export/testData/no_package.kt

@@ -0,0 +1 @@
+fun meaningOfLife(): Int = 420

plugins/swift-export/tests-gen/org/jetbrains/kotlin/swiftexport/SwiftExportCompilerPluginTest.java

@@ -25,6 +25,12 @@ public class SwiftExportCompilerPluginTest extends AbstractSwiftExportContextTes
         KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("plugins/swift-export/testData"), Pattern.compile("^(.+)\\.kt$"), Pattern.compile(".*\\.golden\\.kt$"), TargetBackend.JVM, false);
     }
 
+    @Test
+    @TestMetadata("no_package.kt")
+    public void testNo_package() throws Exception {
+        runTest("plugins/swift-export/testData/no_package.kt");
+    }
+
     @Test
     @TestMetadata("simple.kt")
     public void testSimple() throws Exception {