select the exact prefix match, even if case-insensitive

java/java-tests/testData/codeInsight/completion/normalSorting/CaseInsensitivePrefixMatch.java

@@ -0,0 +1,9 @@
+class Foo {
+  void foo1() {}
+  void foo2() {}
+
+  {
+    foo<caret>
+  }
+
+}

java/java-tests/testSrc/com/intellij/codeInsight/completion/NormalCompletionOrderingTest.java

@@ -249,4 +249,14 @@ public class NormalCompletionOrderingTest extends CompletionSortingTestCase {
     assertEquals(((JavaPsiClassReferenceElement)items.get(1)).getQualifiedName(), "bar.Bar");
   }
 
+  public void testCaseInsensitivePrefixMatch() {
+    CodeInsightSettings.getInstance().COMPLETION_CASE_SENSITIVE = CodeInsightSettings.NONE;
+    try {
+      checkPreferredItems(0, "Foo", "foo1", "foo2");
+    }
+    finally {
+      CodeInsightSettings.getInstance().COMPLETION_CASE_SENSITIVE = CodeInsightSettings.FIRST_LETTER;
+    }
+  }
+
 }

platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/LookupImpl.java

@@ -427,7 +427,8 @@ public class LookupImpl extends LightweightHint implements LookupEx, Disposable
     if (!model.isEmpty()) {
       myList.setFixedCellWidth(Math.max(myLookupTextWidth + myCellRenderer.getIconIndent(), myAdComponent.getAdComponent().getPreferredSize().width));
 
-      if (isFocused() && (!isExactPrefixItem(model.iterator().next(), true) || mySelectionTouched)) {
+      LookupElement first = model.iterator().next();
+      if (isFocused() && (!(isExactPrefixItem(first, true) || isExactPrefixItem(first, false)) || mySelectionTouched)) {
         restoreSelection(oldSelected, hasPreselected, oldInvariant, snapshot.second);
       }
       else {