Improve performance by invoke KFunction by "call".

pom.xml

@@ -114,7 +114,6 @@
     </dependencies>
 
     <build>
-        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
         <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
         <plugins>
             <plugin>
@@ -167,6 +166,10 @@
                 <configuration>
                     <showDeprecation>true</showDeprecation>
                     <showWarnings>true</showWarnings>
+                    <includes>
+                        <include>${project.basedir}/src/main/kotlin</include>
+                        <include>${project.basedir}/src/main/java</include>
+                    </includes>
                 </configuration>
             </plugin>
 

src/main/java/com/fasterxml/jackson/module/kotlin/SpreadWrapper.java

@@ -0,0 +1,10 @@
+package com.fasterxml.jackson.module.kotlin;
+
+import kotlin.reflect.KFunction;
+
+class SpreadWrapper {
+    // Wrapper to avoid costly calls using spread operator.
+    static <T> T call(KFunction<T> function, Object[] args) {
+        return function.call(args);
+    }
+}

src/main/kotlin/com/fasterxml/jackson/module/kotlin/ArgumentBucket.kt

@@ -0,0 +1,47 @@
+package com.fasterxml.jackson.module.kotlin
+
+import java.util.AbstractMap.SimpleEntry as Entry
+import kotlin.reflect.KParameter
+
+internal class ArgumentBucket(private val parameters: List<KParameter>) : Map<KParameter, Any?> {
+    // This array is sorted by KParameter::index.
+    val valueArray: Array<Any?> = arrayOfNulls(parameters.size)
+    private val initializationStatuses: BooleanArray = BooleanArray(parameters.size)
+    private var count = 0
+
+    operator fun set(key: KParameter, value: Any?): Any? {
+        return valueArray[key.index].apply {
+            valueArray[key.index] = value
+
+            if (!initializationStatuses[key.index]) {
+                initializationStatuses[key.index] = true
+                count++
+            }
+        }
+    }
+
+    fun isFullInitialized(): Boolean = parameters.size == count
+
+    override val entries: Set<Map.Entry<KParameter, Any?>>
+        get() = valueArray.withIndex()
+                .filter { (i, _) -> initializationStatuses[i] }
+                .map { (i, arg) -> Entry(parameters[i], arg) }
+                .toSet()
+    override val keys: Set<KParameter>
+        get() = parameters
+                .filterIndexed { i, _ -> initializationStatuses[i] }
+                .toSet()
+    override val size: Int
+        get() = count
+    override val values: Collection<Any?>
+        get() = valueArray.filterIndexed { i, _ -> initializationStatuses[i] }
+
+    override fun containsKey(key: KParameter): Boolean = initializationStatuses[key.index]
+
+    override fun containsValue(value: Any?): Boolean = valueArray.withIndex()
+            .any { (i, arg) -> initializationStatuses[i] && value == arg }
+
+    override fun get(key: KParameter): Any? = valueArray[key.index]
+
+    override fun isEmpty(): Boolean = count == 0
+}

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinValueInstantiator.kt

@@ -162,13 +162,18 @@ internal class KotlinValueInstantiator(
             ) {
                 callable.isAccessible = true
             }
-            val callableParametersByName = linkedMapOf<KParameter, Any?>()
-            callableParameters.mapIndexed { idx, paramDef ->
-                if (paramDef != null) {
-                    callableParametersByName[paramDef] = jsonParamValueList[idx]
+            ArgumentBucket(callable.parameters).apply {
+                callableParameters.forEachIndexed { idx, paramDef ->
+                    if (paramDef != null) {
+                        this[paramDef] = jsonParamValueList[idx]
+                    }
                 }
+            }.let {
+                if (it.isFullInitialized())
+                    SpreadWrapper.call(callable, it.valueArray)
+                else
+                    callable.callBy(it)
             }
-            callable.callBy(callableParametersByName)
         }
 
     }