[NI] Fix determination of completion mode. #KT-30406 Fixed

compiler/testData/diagnostics/tests/controlStructures/kt30406.kt

@@ -0,0 +1,16 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !CHECK_TYPE
+// Issue: KT-30406
+
+interface Option<out T> {
+    val s: String
+}
+class Some<T>(override val s: String) : Option<T>
+class None(override val s: String = "None") : Option<Int>
+
+fun test(a: Int): Option<Any> =
+    <!DEBUG_INFO_EXPRESSION_TYPE("Option<kotlin.Any>")!>if (a == 239)
+        <!DEBUG_INFO_EXPRESSION_TYPE("Some<kotlin.Any>")!>Some("239")<!>
+    else
+        <!DEBUG_INFO_EXPRESSION_TYPE("None")!>None()<!><!>

compiler/testData/diagnostics/tests/controlStructures/kt30406.txt

@@ -0,0 +1,26 @@
+package
+
+public fun test(/*0*/ a: kotlin.Int): Option<kotlin.Any>
+
+public final class None : Option<kotlin.Int> {
+    public constructor None(/*0*/ s: kotlin.String = ...)
+    public open override /*1*/ val s: kotlin.String
+    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 interface Option</*0*/ out T> {
+    public abstract val s: kotlin.String
+    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 Some</*0*/ T> : Option<T> {
+    public constructor Some</*0*/ T>(/*0*/ s: kotlin.String)
+    public open override /*1*/ val s: kotlin.String
+    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
+}