Override omitting parentheses on tab char if they are already placed

idea/src/org/jetbrains/jet/plugin/completion/handlers/JetFunctionInsertHandler.kt

@@ -77,12 +77,15 @@ public class JetFunctionInsertHandler(val caretPosition : CaretPosition, val bra
         val document = context.getDocument()
         val completionChar = context.getCompletionChar()
 
-        val braces = bracketType == BracketType.BRACES && completionChar != '('
+        var documentText = document.getText()
+
+        val forceParenthesis = bracketType == BracketType.BRACES && completionChar == '\t' && documentText.charAt(offset) == '('
+
+        val braces = bracketType == BracketType.BRACES && completionChar != '(' && !forceParenthesis
 
         val openingBracket = if (braces) '{' else '('
         val closingBracket = if (braces) '}' else ')'
 
-        var documentText = document.getText()
         var openingBracketIndex = indexOfSkippingSpace(documentText, openingBracket, offset)
         var inBracketsShift = 0
         if (openingBracketIndex == -1) {

idea/testData/completion/handlers/ForceParenthesisForTabChar.kt

@@ -0,0 +1,8 @@
+package testing
+
+fun some(f: () -> Unit) = 12
+fun other() = 12
+
+fun test() {
+    som<caret>other()
+}

idea/testData/completion/handlers/ForceParenthesisForTabChar.kt.after

@@ -0,0 +1,8 @@
+package testing
+
+fun some(f: () -> Unit) = 12
+fun other() = 12
+
+fun test() {
+    some(<caret>)
+}

idea/tests/org/jetbrains/jet/completion/handlers/CompletionHandlerTest.kt

@@ -30,8 +30,8 @@ import com.intellij.codeInsight.lookup.LookupManager
 import com.intellij.codeInsight.lookup.LookupElementPresentation
 import org.junit.Assert
 import com.intellij.openapi.application.Result
-import kotlin.properties.Delegates
 import com.intellij.testFramework.fixtures.JavaCodeInsightTestFixture
+import kotlin.properties.Delegates
 
 public class CompletionHandlerTest() : JetLightCodeInsightFixtureTestCase() {
     fun testClassCompletionImport() = doTest(CompletionType.BASIC, 2, "SortedSet", null, '\n')
@@ -68,6 +68,8 @@ public class CompletionHandlerTest() : JetLightCodeInsightFixtureTestCase() {
 
     fun testHigherOrderFunctionWithArg() = doTest(CompletionType.BASIC, 2, "filterNot", null, '\n')
 
+    fun testForceParenthesisForTabChar() = doTest(CompletionType.BASIC, 0, "some", null, '\t')
+
     var fixture by Delegates.notNull<JavaCodeInsightTestFixture>()
 
     protected override fun setUp() {