KT-15734

Combine nullability for nested type alias expansion result.

compiler/testData/diagnostics/tests/typealias/kt15734.kt

@@ -0,0 +1,19 @@
+@Target(AnnotationTarget.TYPE)
+annotation class Ann
+
+typealias TString = String
+
+typealias TNString = TString?
+
+typealias TNAString = @Ann TString?
+
+val test1: TNString = TODO()
+val test2: TNAString = TODO()
+val test3: List<TNString> = TODO()
+val test4: List<TNAString> = TODO()
+val test5: List<TNString<!REDUNDANT_NULLABLE!>?<!>> = TODO()
+val test6: () -> List<TNString> = TODO()
+
+fun test(x: TNString) {
+    x<!UNSAFE_CALL!>.<!>hashCode()
+}

compiler/testData/diagnostics/tests/typealias/kt15734.txt

@@ -0,0 +1,19 @@
+package
+
+public val test1: TNString /* = kotlin.String? */
+public val test2: TNAString /* = @Ann kotlin.String? */
+public val test3: kotlin.collections.List<TNString /* = kotlin.String? */>
+public val test4: kotlin.collections.List<TNAString /* = @Ann kotlin.String? */>
+public val test5: kotlin.collections.List<TNString? /* = kotlin.String? */>
+public val test6: () -> kotlin.collections.List<TNString /* = kotlin.String? */>
+public fun test(/*0*/ x: TNString /* = kotlin.String? */): kotlin.Unit
+
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.TYPE}) public final annotation class Ann : kotlin.Annotation {
+    public constructor Ann()
+    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 typealias TNAString = @Ann TString?
+public typealias TNString = TString?
+public typealias TString = kotlin.String