KT-12305 Fix passing single argument to native vararg function

js/js.translator/src/org/jetbrains/kotlin/js/translate/reference/CallArgumentTranslator.kt

@@ -115,7 +115,12 @@ class CallArgumentTranslator private constructor(
                     }
                 }
                 else {
-                    kind = translateVarargArgument(arguments, result, argContext, !isNativeFunctionCall)
+                    kind = if (isNativeFunctionCall) {
+                        translateValueArguments(arguments, result, argContext)
+                    }
+                    else {
+                        translateVarargArgument(arguments, result, argContext, true)
+                    }
                 }
             }
             else {

js/js.translator/testData/native/cases/vararg.kt

@@ -72,6 +72,8 @@ fun box(): String {
     if (paramCount() != 0)
         return "failed when call native function without args"
 
+    if (paramCount(1) != 1) return "failed when call native function with single vararg"
+
     if (paramCount(1, 2, 3) != 3)
         return "failed when call native function with some args"
 
@@ -93,6 +95,12 @@ fun box(): String {
     if (!spreadInMethodCall(2, 1, 2))
         return "failed when call method using spread operator"
 
+    if (!Bar(1).test(0, 1, 1))
+        return "failed when call method with single arg"
+
+    if (!spreadInMethodCall(2, 1, 2))
+        return "failed when call method using spread operator"
+
     if (!(obj.test(5, 1, 2, 3, 4, 5)))
         return "failed when call method of object"