Feature: added the experimental not null and null function.

kotlinshaver/src/main/java/com/devrapid/kotlinshaver/Kits.kt

@@ -2,6 +2,9 @@
 
 package com.devrapid.kotlinshaver
 
+import kotlin.contracts.ExperimentalContracts
+import kotlin.contracts.contract
+
 /**
  *
  * @author  jieyi
@@ -10,7 +13,7 @@ package com.devrapid.kotlinshaver
 inline infix fun (() -> Unit).iff(condition: Any?): Any? {
     return when (condition) {
         is Boolean -> if (condition) this() else null
-        is Float, Double, Int, Long -> condition.let { this() }
+        is Float, Double, Int, Long -> this()
         is String -> if (condition.isNotBlank()) this() else null
         is Collection<*> -> if (condition.isNotEmpty()) this() else null
         else -> condition?.let { this() }
@@ -20,3 +23,19 @@ inline infix fun (() -> Unit).iff(condition: Any?): Any? {
 inline fun Any?.isNull() = null == this
 
 inline fun Any?.isNotNull() = null != this
+
+@ExperimentalContracts
+inline fun Any?.isNullExp(): Boolean {
+    contract {
+        returns(false) implies (this@isNullExp == null)
+    }
+    return null == this
+}
+
+@ExperimentalContracts
+inline fun Any?.isNotNullExp(): Boolean {
+    contract {
+        returns(true) implies (this@isNotNullExp != null)
+    }
+    return null != this
+}