directly wrap in non-empty Collection type

Author: balazstothofficial

src/commonMain/kotlin/com/quickbirdstudios/nonEmptyCollection/set/NonEmptySet.kt

@@ -15,4 +15,10 @@ class NonEmptySet<T> internal constructor(
     override fun equals(other: Any?): Boolean = full == other
 
     override fun hashCode(): Int = full.hashCode()
+
+    init {
+        require(full.isNotEmpty()) {
+            "Fatal Error! This is a bug. Please contact the library author."
+        }
+    }
 }

src/commonMain/kotlin/com/quickbirdstudios/nonEmptyCollection/unsafe/toNonEmptyCollection.kt

@@ -9,7 +9,7 @@ import com.quickbirdstudios.nonEmptyCollection.set.nonEmptySetOf
 
 @UnsafeNonEmptyCollectionApi
 fun <T> Iterable<T>.toNonEmptyList(): NonEmptyList<T> = isAlreadyNonEmptyOr {
-    nonEmptyListOf(first(), drop(1))
+    NonEmptyList(toList())
 }
 
 @UnsafeNonEmptyCollectionApi
@@ -19,8 +19,7 @@ fun <T> Iterable<T>.toNonEmptySet(): NonEmptySet<T> = isAlreadyNonEmptyOr {
 
 @UnsafeNonEmptyCollectionApi
 fun <T> Set<T>.toNonEmptySet(): NonEmptySet<T> = isAlreadyNonEmptyOr {
-    val first = first()
-    nonEmptySetOf(first, this - first)
+    NonEmptySet(this)
 }
 
 @UnsafeNonEmptyCollectionApi
@@ -30,9 +29,7 @@ fun <K, V> Iterable<Pair<K, V>>.toNonEmptyMap(): NonEmptyMap<K, V> = isAlreadyNo
 
 @UnsafeNonEmptyCollectionApi
 fun <K, V> Map<K, V>.toNonEmptyMap(): NonEmptyMap<K, V> = isAlreadyNonEmptyOr {
-    val first = entries.first()
-
-    nonEmptyMapOf(first.key to first.value, this - first.key)
+    NonEmptyMap(this)
 }
 
 private inline fun <Empty, reified NonEmpty> Empty.isAlreadyNonEmptyOr(

src/jvmTest/kotlin/com/quickbirdstudios/nonEmptyCollection/unsafe/ToNonEmptyCollectionTest.kt

@@ -15,7 +15,7 @@ class ToNonEmptyCollectionTest {
     @Test
     fun toNonEmptyList() {
         assertEquals(nonEmptyListOf(15, 2), listOf(15, 2).toNonEmptyList())
-        assertThrows<NoSuchElementException> {
+        assertThrows<IllegalArgumentException> {
             emptyList<String>().toNonEmptyList()
         }
     }
@@ -25,10 +25,10 @@ class ToNonEmptyCollectionTest {
         assertEquals(nonEmptySetOf(15, 2), listOf(15, 2).toNonEmptySet())
         assertEquals(nonEmptySetOf(15, 2), setOf(15, 2).toNonEmptySet())
 
-        assertThrows<NoSuchElementException> {
+        assertThrows<IllegalArgumentException> {
             emptyList<String>().toNonEmptySet()
         }
-        assertThrows<NoSuchElementException> {
+        assertThrows<IllegalArgumentException> {
             emptySet<String>().toNonEmptySet()
         }
     }
@@ -44,10 +44,10 @@ class ToNonEmptyCollectionTest {
             mapOf(15 to 't', 2 to 'P').toNonEmptyMap()
         )
 
-        assertThrows<NoSuchElementException> {
+        assertThrows<IllegalArgumentException> {
             emptyList<Pair<String, Float>>().toNonEmptyMap()
         }
-        assertThrows<NoSuchElementException> {
+        assertThrows<IllegalArgumentException> {
             emptyMap<String, Double>().toNonEmptyMap()
         }
     }