Refactored tests using Array constructor:

Some moved to tests with stdlib
Some changed to use arrayOfNulls

compiler/testData/diagnostics/tests/regressions/kt312.kt

@@ -1,3 +1,6 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+public inline fun <reified T> Array(n: Int, block: (Int) -> T): Array<T> = null!!
+
 // KT-312 Nullability problem when a nullable version of a generic type is returned
 
 fun <T> Array<out T>.safeGet(index : Int) : T<!BASE_WITH_NULLABLE_UPPER_BOUND!>?<!> {

compiler/testData/diagnostics/tests/regressions/kt312.txt

@@ -3,4 +3,5 @@ package
 internal val args: kotlin.Array<kotlin.String>
 internal val name: kotlin.String
 internal val name1: kotlin.String?
+kotlin.inline() public fun </*0*/ reified T> Array(/*0*/ n: kotlin.Int, /*1*/ block: (kotlin.Int) -> T): kotlin.Array<T>
 internal fun </*0*/ T> kotlin.Array<out T>.safeGet(/*0*/ index: kotlin.Int): T?