New J2K: use nullable type for unknown for public declarations & prepare for mutability inference

#KT-32518 fixed

nj2k/testData/newJ2k/function/classGenericParam.kt

@@ -1,2 +1,2 @@
-val t: T?
+val t: T
     get() {}

nj2k/testData/newJ2k/function/externalKtFunctionalInterface.kt

@@ -11,6 +11,6 @@ internal class Test {
     fun nya(): Double {
         //TODO explicitlly call apply here
 
-        return foo(1, FunctionalI<Int?, Double?> { x: Int -> this.toDouble(x) })
+        return foo(1, FunctionalI<Int, Double> { x: Int -> this.toDouble(x) })
     }
 }

nj2k/testData/newJ2k/function/internalFunctionalInterface.kt

@@ -14,6 +14,6 @@ internal class Test {
     }
 
     fun nya(): Double {
-        return foo(1, FunctionalI<Int?, Double?> { x: A -> this.toDouble(x) })
+        return foo(1, FunctionalI<Int, Double> { x: A -> this.toDouble(x) })
     }
 }

nj2k/testData/newJ2k/function/java8Lambdas.kt

@@ -1,7 +1,7 @@
 class Java8Class {
-    fun foo0(r: Function0<String>) {}
-    fun foo1(r: Function1<Int, String?>) {}
-    fun foo2(r: Function2<Int, Int, String>) {}
+    fun foo0(r: Function0<String?>?) {}
+    fun foo1(r: Function1<Int, String?>?) {}
+    fun foo2(r: Function2<Int?, Int?, String?>?) {}
     fun helper() {}
     fun foo() {
         foo0 { "42" }
@@ -10,8 +10,8 @@ class Java8Class {
             helper()
             "42"
         }
-        foo1 { i: Int -> "42" }
-        foo1 { i: Int -> "42" }
+        foo1 { i: Int? -> "42" }
+        foo1 { i: Int? -> "42" }
         foo1 { i: Int ->
             helper()
             if (i > 1) {
@@ -19,12 +19,12 @@ class Java8Class {
             }
             "43"
         }
-        foo2 { i: Int, j: Int -> "42" }
-        foo2 { i: Int, j: Int ->
+        foo2 { i: Int?, j: Int? -> "42" }
+        foo2 { i: Int?, j: Int? ->
             helper()
             "42"
         }
-        val f = label@{ i: Int, k: Int ->
+        val f: Function2<Int, Int, String> = label@{ i: Int, k: Int? ->
             helper()
             if (i > 1) {
                 return@label "42"
@@ -32,7 +32,7 @@ class Java8Class {
             "43"
         }
         val f1 = label@{ i1: Int, k1: Int ->
-            val f2 = label@{ i2: Int, k2: Int ->
+            val f2: Function2<Int, Int, String> = label@{ i2: Int, k2: Int? ->
                 helper()
                 if (i2 > 1) {
                     return@label "42"

nj2k/testData/newJ2k/function/methodClassType.kt

@@ -1 +1 @@
-fun main(): String? {}
+fun main(): String {}

nj2k/testData/newJ2k/function/referenceToConstructor.kt

@@ -4,7 +4,7 @@ import java.util.stream.Collectors
 object TestLambda {
     @JvmStatic
     fun main(args: Array<String>) {
-        val names: List<String> = Arrays.asList("A", "B")
-        val people: List<Person?> = names.stream().map { name: String -> Person(name) }.collect(Collectors.toList())
+        val names = Arrays.asList("A", "B")
+        val people = names.stream().map { name: String? -> Person(name) }.collect(Collectors.toList())
     }
-}
+}

nj2k/testData/newJ2k/function/varVararg.kt

@@ -1,8 +1,8 @@
 package demo
 
 internal class Test {
-    fun test(vararg args: Any) {
+    fun test(vararg args: Any?) {
         var args = args
-        args = arrayOf(1, 2, 3)
+        args = arrayOf<Int?>(1, 2, 3)
     }
 }