IterateExpressionIntention uses collection expression for name suggestions too

idea/idea-core/src/org/jetbrains/kotlin/idea/core/KotlinNameSuggester.kt

@@ -72,6 +72,23 @@ public object KotlinNameSuggester {
         return result
     }
 
+    public fun suggestIterationVariableNames(collection: JetExpression, elementType: JetType, validator: (String) -> Boolean, defaultName: String?): Collection<String> {
+        val result = LinkedHashSet<String>()
+
+        suggestNamesByExpressionOnly(collection, { true })
+                .map { StringUtil.unpluralize(it) }
+                .filterNotNull()
+                .mapTo(result) { suggestNameByName(it, validator) }
+
+        result.addNamesByType(elementType, validator)
+
+        if (result.isEmpty()) {
+            result.addName(defaultName, validator)
+        }
+
+        return result
+    }
+
     private val COMMON_TYPE_PARAMETER_NAMES = listOf("T", "U", "V", "W", "X", "Y", "Z")
 
     public fun suggestNamesForTypeParameters(count: Int, validator: (String) -> Boolean): List<String> {

idea/src/org/jetbrains/kotlin/idea/intentions/ChooseValueExpression.kt

@@ -32,7 +32,7 @@ import com.intellij.psi.impl.source.tree.injected.InjectedLanguageUtil
 
 //TODO: move it somewhere else and reuse
 public abstract class ChooseValueExpression<T : Any>(
-        lookupItems: List<T>,
+        lookupItems: Collection<T>,
         protected val defaultItem: T,
         private val advertisementText: String? = null
 ) : Expression() {
@@ -65,8 +65,8 @@ public abstract class ChooseValueExpression<T : Any>(
 }
 
 public class ChooseStringExpression(
-        suggestions: List<String>,
+        suggestions: Collection<String>,
-        default: String = suggestions[0],
+        default: String = suggestions.first(),
         advertisementText: String? = null
 ) : ChooseValueExpression<String>(suggestions, default, advertisementText) {
     override fun getLookupString(element: String) = element

idea/src/org/jetbrains/kotlin/idea/intentions/IterateExpressionIntention.kt

@@ -57,11 +57,10 @@ public class IterateExpressionIntention : JetSelfTargetingIntention<JetExpressio
         //TODO: multi-declaration (when?)
 
         val elementType = data(element)!!.elementType
-        //TODO: base on expression too
         //TODO: name validation
-        val names = KotlinNameSuggester.suggestNamesByType(elementType, { true }, "e")
+        val names = KotlinNameSuggester.suggestIterationVariableNames(element, elementType, { true }, "e")
 
-        var forExpression = JetPsiFactory(element).createExpressionByPattern("for($0 in $1) {\nx\n}", names[0], element) as JetForExpression
+        var forExpression = JetPsiFactory(element).createExpressionByPattern("for($0 in $1) {\nx\n}", names.first(), element) as JetForExpression
         forExpression = element.replaced(forExpression)
 
         PsiDocumentManager.getInstance(forExpression.getProject()).doPostponedOperationsAndUnblockDocument(editor.getDocument())

idea/testData/intentions/iterateExpression/nameSuggestion.kt

@@ -0,0 +1,3 @@
+fun foo(names: List<String>) {
+    names<caret>
+}

idea/testData/intentions/iterateExpression/nameSuggestion.kt.after

@@ -0,0 +1,5 @@
+fun foo(names: List<String>) {
+    for (name in names) {
+        <caret>
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -5235,6 +5235,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("nameSuggestion.kt")
+        public void testNameSuggestion() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/iterateExpression/nameSuggestion.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("simple.kt")
         public void testSimple() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/iterateExpression/simple.kt");