Address the review

Author: dkhalanskyjb

core/common/test/InstantTest.kt

@@ -559,6 +559,12 @@ class InstantRangeTest {
             assertArithmeticFails("$instant") { instant.plus(Long.MAX_VALUE, DateTimeUnit.YEAR, UTC) }
             assertArithmeticFails("$instant") { instant.plus(Long.MIN_VALUE, DateTimeUnit.YEAR, UTC) }
         }
+        for (instant in smallInstants) {
+            instant.plus(2 * Int.MAX_VALUE.toLong(), DateTimeUnit.DAY, UTC)
+            instant.plus(2 * Int.MIN_VALUE.toLong(), DateTimeUnit.DAY, UTC)
+            instant.plus(2 * Int.MAX_VALUE.toLong(), DateTimeUnit.MONTH, UTC)
+            instant.plus(2 * Int.MIN_VALUE.toLong(), DateTimeUnit.MONTH, UTC)
+        }
         // Overflowing a LocalDateTime in input
         maxValidInstant.plus(-1, DateTimeUnit.NANOSECOND, UTC)
         minValidInstant.plus(1, DateTimeUnit.NANOSECOND, UTC)

core/commonKotlin/src/Instant.kt

@@ -192,7 +192,7 @@ private fun Instant.check(zone: TimeZone): Instant = this@check.also {
 public actual fun Instant.plus(period: DateTimePeriod, timeZone: TimeZone): Instant = try {
     with(period) {
         val withDate = toZonedDateTimeFailing(timeZone)
-            .run { if (totalMonths != 0L) plus(totalMonths.toLong(), DateTimeUnit.MONTH) else this }
+            .run { if (totalMonths != 0L) plus(totalMonths, DateTimeUnit.MONTH) else this }
             .run { if (days != 0) plus(days.toLong(), DateTimeUnit.DAY) else this }
         withDate.toInstant()
             .run { if (totalNanoseconds != 0L) plus(0, totalNanoseconds).check(timeZone) else this }
@@ -212,11 +212,8 @@ public actual fun Instant.minus(value: Int, unit: DateTimeUnit, timeZone: TimeZo
     plus(-value.toLong(), unit, timeZone)
 public actual fun Instant.plus(value: Long, unit: DateTimeUnit, timeZone: TimeZone): Instant = try {
     when (unit) {
-        is DateTimeUnit.DateBased -> {
-            if (value < Int.MIN_VALUE || value > Int.MAX_VALUE)
-                throw ArithmeticException("Can't add a Long date-based value, as it would cause an overflow")
+        is DateTimeUnit.DateBased ->
             toZonedDateTimeFailing(timeZone).plus(value, unit).toInstant()
-        }
         is DateTimeUnit.TimeBased ->
             check(timeZone).plus(value, unit).check(timeZone)
     }

core/commonKotlin/src/TimeZone.kt

@@ -21,11 +21,7 @@ public actual open class TimeZone internal constructor() {
         public actual fun currentSystemDefault(): TimeZone {
             // TODO: probably check if currentSystemDefault name is parseable as FixedOffsetTimeZone?
             val (name, zone) = currentSystemDefaultZone()
-            return if (zone == null) {
-                of(name)
-            } else {
-                zone
-            }
+            return zone ?: of(name)
         }
 
         public actual val UTC: FixedOffsetTimeZone = UtcOffset.ZERO.asTimeZone()

core/wasmJs/src/PlatformSpecifics.kt

@@ -4,7 +4,6 @@
  */
 package kotlinx.datetime.internal
 
-import kotlinx.datetime.internal.JSJoda.ZoneId
 import kotlinx.datetime.internal.JSJoda.ZoneRulesProvider
 import kotlin.js.unsafeCast