Avoid relying on 22 max function parameters count in ObjCExport frontend (#3235)

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/CustomTypeMapper.kt

@@ -6,8 +6,12 @@
 package org.jetbrains.kotlin.backend.konan.objcexport
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
+import org.jetbrains.kotlin.builtins.getFunctionalClassKind
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.resolve.descriptorUtil.classId
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
 
@@ -22,7 +26,7 @@ internal object CustomTypeMappers {
      *
      * Don't forget to update [hiddenTypes] after adding new one.
      */
-    val byClassId: Map<ClassId, CustomTypeMapper> = with(KotlinBuiltIns.FQ_NAMES) {
+    private val predefined: Map<ClassId, CustomTypeMapper> = with(KotlinBuiltIns.FQ_NAMES) {
         val result = mutableListOf<CustomTypeMapper>()
 
         result += Collection(list, "NSArray")
@@ -43,13 +47,34 @@ internal object CustomTypeMappers {
 
         result += Simple(ClassId.topLevel(string.toSafe()), "NSString")
 
-        (0..ObjCExportMapper.maxFunctionTypeParameterCount).forEach {
-            result += Function(it)
-        }
-
         result.associateBy { it.mappedClassId }
     }
 
+    fun hasMapper(descriptor: ClassDescriptor): Boolean {
+        // Should be equivalent to `getMapper(descriptor) != null`.
+        if (descriptor.classId in predefined) return true
+        if (descriptor.isMappedFunctionClass()) return true
+        return false
+    }
+
+    fun getMapper(descriptor: ClassDescriptor): CustomTypeMapper? {
+        val classId = descriptor.classId
+
+        predefined[classId]?.let { return it }
+
+        if (descriptor.isMappedFunctionClass()) {
+            // TODO: somewhat hacky, consider using FunctionClassDescriptor.arity later.
+            val arity = descriptor.declaredTypeParameters.size - 1 // Type parameters include return type.
+            assert(classId == KotlinBuiltIns.getFunctionClassId(arity))
+            return Function(arity)
+        }
+
+        return null
+    }
+
+    private fun ClassDescriptor.isMappedFunctionClass() =
+            this.getFunctionalClassKind() == FunctionClassDescriptor.Kind.Function
+
     /**
      * Types to be "hidden" during mapping, i.e. represented as `id`.
      *
@@ -109,8 +134,9 @@ internal object CustomTypeMappers {
         }
     }
 
-    private class Function(parameterCount: Int) : CustomTypeMapper {
-        override val mappedClassId: ClassId = KotlinBuiltIns.getFunctionClassId(parameterCount)
+    private class Function(private val parameterCount: Int) : CustomTypeMapper {
+        override val mappedClassId: ClassId
+            get() = KotlinBuiltIns.getFunctionClassId(parameterCount)
 
         override fun mapType(mappedSuperType: KotlinType, translator: ObjCExportTranslatorImpl, objCExportScope: ObjCExportScope): ObjCNonNullReferenceType {
             return translator.mapFunctionTypeIgnoringNullability(mappedSuperType, objCExportScope, returnsVoid = false)

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportHeaderGenerator.kt

@@ -756,7 +756,7 @@ internal class ObjCExportTranslatorImpl(
 
         val typeMappingMatches = (listOf(kotlinType) + kotlinType.supertypes()).mapNotNull { type ->
             (type.constructor.declarationDescriptor as? ClassDescriptor)?.let { descriptor ->
-                mapper.customTypeMappers[descriptor.classId]?.let { mapper ->
+                mapper.getCustomTypeMapper(descriptor)?.let { mapper ->
                     TypeMappingMatch(type, descriptor, mapper)
                 }
             }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportMapper.kt

@@ -31,13 +31,14 @@ internal class ObjCExportMapper(
         val maxFunctionTypeParameterCount get() = KONAN_FUNCTION_INTERFACES_MAX_PARAMETERS
     }
 
-    val customTypeMappers: Map<ClassId, CustomTypeMapper> get() = CustomTypeMappers.byClassId
+    fun getCustomTypeMapper(descriptor: ClassDescriptor): CustomTypeMapper? = CustomTypeMappers.getMapper(descriptor)
+
     val hiddenTypes: Set<ClassId> get() = CustomTypeMappers.hiddenTypes
 
     fun isSpecialMapped(descriptor: ClassDescriptor): Boolean {
         // TODO: this method duplicates some of the [ObjCExportTranslatorImpl.mapReferenceType] logic.
         return KotlinBuiltIns.isAny(descriptor) ||
-                descriptor.getAllSuperClassifiers().any { it.classId in customTypeMappers }
+                descriptor.getAllSuperClassifiers().any { it is ClassDescriptor && CustomTypeMappers.hasMapper(it) }
     }
 
     private val methodBridgeCache = mutableMapOf<FunctionDescriptor, MethodBridge>()