Implicit nothing type argument: handle nullable case properly

#KT-41620 Fixed

compiler/testData/diagnostics/tests/inference/nothingType/genericOverride.fir.kt

@@ -0,0 +1,12 @@
+interface A {
+    fun a(): A
+}
+
+fun error(s: String): Nothing = null!!
+
+class A1 : A {
+    override fun a() = test() ?: error("")
+
+    @Suppress("UNCHECKED_CAST")
+    private fun <V : A> test(): V? = this as? V
+}

compiler/testData/diagnostics/tests/inference/nothingType/genericOverride.kt

@@ -0,0 +1,12 @@
+interface A {
+    fun a(): A
+}
+
+fun error(s: String): Nothing = null!!
+
+class A1 : A {
+    override fun a() = <!IMPLICIT_NOTHING_TYPE_ARGUMENT_IN_RETURN_POSITION!>test<!>() ?: error("")
+
+    @Suppress("UNCHECKED_CAST")
+    private fun <V : A> test(): V? = this as? V
+}

compiler/testData/diagnostics/tests/inference/nothingType/genericOverride.txt

@@ -0,0 +1,19 @@
+package
+
+public fun error(/*0*/ s: kotlin.String): kotlin.Nothing
+
+public interface A {
+    public abstract fun a(): A
+    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 A1 : A {
+    public constructor A1()
+    public open override /*1*/ fun a(): kotlin.Nothing
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    @kotlin.Suppress(names = {"UNCHECKED_CAST"}) private final fun </*0*/ V : A> test(): V?
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/inference/nothingType/notEnoughInformationFromNullabilityConstraint.kt

@@ -10,7 +10,7 @@ fun test() {
         <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER{NI}, TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER{OI}!>make<!>()
     )
 
-    select(make(), null)
+    select(<!IMPLICIT_NOTHING_TYPE_ARGUMENT_IN_RETURN_POSITION!>make<!>(), null)
 
-    <!TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT{OI}!>if<!> (true) <!TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH{OI}!>make()<!> else TODO()
+    <!TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT{OI}!>if<!> (true) <!TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH{OI}!><!IMPLICIT_NOTHING_TYPE_ARGUMENT_IN_RETURN_POSITION!>make<!>()<!> else TODO()
 }