[NI] Discriminate Nothing? result type from nullability constraints

Nullability constraints should not be chosen when proper
argument constraints for variables in contravariant position present.

^KT-32106 Fixed
^KT-33166 Fixed

compiler/testData/diagnostics/tests/inference/nestedCalls/preferArgumentToNullability.fir.kt

@@ -0,0 +1,15 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+open class Cls
+
+abstract class In<in I>
+class SubIn : In<Cls?>()
+
+inline fun <reified T : Cls> materialize(): T? = TODO()
+
+fun <D> transform(transformer: In<D>, data: D): Unit = TODO()
+
+fun test(subIn: SubIn) {
+    transform(subIn, materialize()) // D should be inferred to Cls?, not Nothing?
+}

compiler/testData/diagnostics/tests/inference/nestedCalls/preferArgumentToNullability.kt

@@ -0,0 +1,15 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+open class Cls
+
+abstract class In<in I>
+class SubIn : In<Cls?>()
+
+inline fun <reified T : Cls> materialize(): T? = TODO()
+
+fun <D> transform(transformer: In<D>, data: D): Unit = TODO()
+
+fun test(subIn: SubIn) {
+    transform(subIn, materialize()) // D should be inferred to Cls?, not Nothing?
+}

compiler/testData/diagnostics/tests/inference/nestedCalls/preferArgumentToNullability.txt

@@ -0,0 +1,26 @@
+package
+
+public inline fun </*0*/ reified T : Cls> materialize(): T?
+public fun test(/*0*/ subIn: SubIn): kotlin.Unit
+public fun </*0*/ D> transform(/*0*/ transformer: In<D>, /*1*/ data: D): kotlin.Unit
+
+public open class Cls {
+    public constructor Cls()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class In</*0*/ in I> {
+    public constructor In</*0*/ in I>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class SubIn : In<Cls?> {
+    public constructor SubIn()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/inference/nestedCalls/preferNothingToBound.fir.kt

@@ -0,0 +1,3 @@
+fun <K> id(arg: K): K = arg
+
+val v = id(null)

compiler/testData/diagnostics/tests/inference/nestedCalls/preferNothingToBound.kt

@@ -0,0 +1,3 @@
+fun <K> id(arg: K): K = arg
+
+val v = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>id(null)<!>

compiler/testData/diagnostics/tests/inference/nestedCalls/preferNothingToBound.txt

@@ -0,0 +1,4 @@
+package
+
+public val v: kotlin.Nothing?
+public fun </*0*/ K> id(/*0*/ arg: K): K