Generate to[Primitive]Array() methods for generic arrays and collections.

#KT-4180 Fixed

libraries/tools/kotlin-stdlib-gen/src/generators/GenerateCollections.kt

@@ -21,6 +21,14 @@ fun generateCollectionsAPI(outDir: File) {
     specialJVM().writeTo(File(outDir, "_SpecialJVM.kt")) { build() }
     ranges().writeTo(File(outDir, "_Ranges.kt")) { build() }
 
+    toPrimitiveArrays().writeTo(File(outDir, "_ArraysToPrimitiveArrays.kt")) {
+        val builder = StringBuilder()
+        for (family in buildFamilies)
+            build(builder, family, buildPrimitives.single())
+
+        builder.toString()
+    }
+
     numeric().writeTo(File(outDir, "_Numeric.kt")) {
         val builder = StringBuilder()
         for (numeric in numericPrimitives)

libraries/tools/kotlin-stdlib-gen/src/templates/Arrays.kt

@@ -56,3 +56,34 @@ fun arrays(): List<GenericFunction> {
 
     return templates
 }
+
+
+
+fun toPrimitiveArrays(): List<GenericFunction> =
+    PrimitiveType.values().map { primitive ->
+        val arrayType = primitive.name + "Array"
+        f("to$arrayType()") {
+            only(ArraysOfObjects, Collections)
+            only(primitive)
+            doc(ArraysOfObjects) { "Returns an array of ${primitive.name} containing all of the elements of this generic array." }
+            doc(Collections) { "Returns an array of ${primitive.name} containing all of the elements of this collection." }
+            returns(arrayType)
+            body {
+                """
+                val result = $arrayType(size())
+                for (index in indices)
+                    result[index] = this[index]
+                return result
+                """
+            }
+            body(Collections) {
+                """
+                val result = $arrayType(size())
+                var index = 0
+                for (element in this)
+                    result[index++] = element
+                return result
+                """
+            }
+        }
+    }