Add varargs tests; show ... before vararg arguments

idea/src/org/jetbrains/kotlin/idea/parameterInfo/KotlinInlayParameterHintsProvider.kt

@@ -126,7 +126,8 @@ private enum class HintType(desc: String, enabled: Boolean) {
                     resolvedArg.arguments.firstOrNull()?.let { arg ->
                         arg.getArgumentExpression()?.let { argExp ->
                             if (!arg.isNamed() && !valueParam.name.isSpecial && argExp.isUnclearExpression()) {
-                                return@mapNotNull InlayInfo(valueParam.name.identifier, argExp.startOffset)
+                                val prefix = if (valueParam.varargElementType != null) "..." else ""
+                                return@mapNotNull InlayInfo(prefix + valueParam.name.identifier, argExp.startOffset)
                             }
                         }
                     }

idea/tests/org/jetbrains/kotlin/idea/parameterInfo/InlayParameterHintsTest.kt

@@ -52,4 +52,44 @@ class InlayParameterHintsTest : KotlinLightCodeInsightFixtureTestCase() {
     val t = IllegalStateException("crime");
   }""")
     }
+
+    fun `test single varargs hint`() {
+        check("""
+  fun main() {
+    testBooleanVarargs(<hint text="test:" />13, <hint text="...booleans:" />false)
+  }
+
+  fun testBooleanVarargs(test: Int, vararg booleans: Boolean): Boolean {
+    return false
+  }
+}
+""")
+    }
+
+    fun `test no hint if varargs null`() {
+        check("""
+  fun main() {
+    testBooleanVarargs(<hint text="test:" />13)
+  }
+
+  fun testBooleanVarargs(test: Int, vararg booleans: Boolean): Boolean {
+    return false
+  }
+""")
+    }
+
+
+    fun `test multiple vararg hint`() {
+        check("""
+  fun main() {
+    testBooleanVarargs(<hint text="test:" />13, <hint text="...booleans:" />false, true, false)
+  }
+
+  fun testBooleanVarargs(test: Int, vararg booleans: Boolean): Boolean {
+    return false
+  }
+""")
+    }
+
+
 }