Don't generate functional types for functions with long signatures (#2349)

The K/N stdlib doesn't contain basic classes (e.g. Functon0,
Function1 etc) for functional types with >22 parameters.
So we cannot convert functional pointers with such signatures
into Kotlin functional types and have to replace them with
opaque pointers.

Fix for GitHub issue #2334.

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/Indexer.kt

@@ -77,7 +77,7 @@ private class ObjCCategoryImpl(
     override val properties = mutableListOf<ObjCProperty>()
 }
 
-internal class NativeIndexImpl(val library: NativeLibrary) : NativeIndex() {
+internal class NativeIndexImpl(val library: NativeLibrary, val verbose: Boolean = false) : NativeIndex() {
 
     private sealed class DeclarationID {
         data class USR(val usr: String) : DeclarationID()
@@ -154,6 +154,12 @@ internal class NativeIndexImpl(val library: NativeLibrary) : NativeIndex() {
 
     override lateinit var includedHeaders: List<HeaderId>
 
+    private fun log(message: String) {
+        if (verbose) {
+            println(message)
+        }
+    }
+
     private fun getDeclarationId(cursor: CValue<CXCursor>): DeclarationID {
         val usr = clang_getCursorUSR(cursor).convertAndDispose()
         if (usr == "") {
@@ -618,6 +624,15 @@ internal class NativeIndexImpl(val library: NativeLibrary) : NativeIndex() {
         } else {
             val returnType = convertType(clang_getResultType(type))
             val numArgs = clang_getNumArgTypes(type)
+
+            // Ignore functions with long signatures since we have no basic class for such functional types in the stdlib.
+            // TODO: Remove this limitation when functional types with long signatures are supported.
+            if (numArgs > 22) {
+                log("Warning: cannot generate a Kotlin functional type for a pointer to a function with more than 22 parameters. " +
+                        "An opaque pointer will be used instead.")
+                return VoidType
+            }
+
             val paramTypes = (0..numArgs - 1).map {
                 convertType(clang_getArgType(type, it))
             }
@@ -902,8 +917,8 @@ internal class NativeIndexImpl(val library: NativeLibrary) : NativeIndex() {
 
 }
 
-fun buildNativeIndexImpl(library: NativeLibrary): NativeIndex {
-    val result = NativeIndexImpl(library)
+fun buildNativeIndexImpl(library: NativeLibrary, verbose: Boolean): NativeIndex {
+    val result = NativeIndexImpl(library, verbose)
     indexDeclarations(result)
     findMacros(result)
     return result

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/NativeIndex.kt

@@ -53,7 +53,7 @@ data class NativeLibrary(val includes: List<String>,
 /**
  * Retrieves the definitions from given C header file using given compiler arguments (e.g. defines).
  */
-fun buildNativeIndex(library: NativeLibrary): NativeIndex = buildNativeIndexImpl(library)
+fun buildNativeIndex(library: NativeLibrary, verbose: Boolean): NativeIndex = buildNativeIndexImpl(library, verbose)
 
 /**
  * This class describes the IR of definitions from C header file(s).

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt

@@ -241,7 +241,7 @@ private fun processCLib(args: Array<String>): Array<String>? {
             target = tool.target
     )
 
-    val nativeIndex = buildNativeIndex(library)
+    val nativeIndex = buildNativeIndex(library, verbose)
 
     val gen = StubGenerator(nativeIndex, configuration, libName, generateShims, verbose, flavor, imports)