less allocations when iterating over lookup strings

platform/lang-impl/src/com/intellij/codeInsight/completion/CompletionUtil.java

@@ -40,6 +40,7 @@ import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.filters.TrueFilter;
 import com.intellij.util.ExceptionUtil;
+import com.intellij.util.UnmodifiableIterator;
 import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.containers.HashMap;
 import org.jetbrains.annotations.NonNls;
@@ -271,14 +272,40 @@ public class CompletionUtil {
     return result;
   }
 
-  public static List<String> getImmutableLookupStrings(@NotNull LookupElement element) {
-    try {
-      return ContainerUtil.newArrayList(element.getAllLookupStrings());
-    }
-    catch (ConcurrentModificationException e) {
-      final Attachment dump = new Attachment("threadDump.txt", ThreadDumper.dumpThreadsToString());
-      throw new LogEventException("Error while traversing lookup strings of " + element + " of " + element.getClass(),
-                                  ExceptionUtil.getThrowableText(e), dump);
-    }
+  public static Iterable<String> iterateLookupStrings(@NotNull final LookupElement element) {
+    return new Iterable<String>() {
+      @NotNull
+      @Override
+      public Iterator<String> iterator() {
+        final Iterator<String> original = element.getAllLookupStrings().iterator();
+        return new UnmodifiableIterator<String>(original) {
+          @Override
+          public boolean hasNext() {
+            try {
+              return super.hasNext();
+            }
+            catch (ConcurrentModificationException e) {
+              throw handleCME(e);
+            }
+          }
+
+          @Override
+          public String next() {
+            try {
+              return super.next();
+            }
+            catch (ConcurrentModificationException e) {
+              throw handleCME(e);
+            }
+          }
+
+          private LogEventException handleCME(ConcurrentModificationException e) {
+            final Attachment dump = new Attachment("threadDump.txt", ThreadDumper.dumpThreadsToString());
+            return new LogEventException("Error while traversing lookup strings of " + element + " of " + element.getClass(),
+                                        ExceptionUtil.getThrowableText(e), dump);
+          }
+        };
+      }
+    };
   }
 }

platform/lang-impl/src/com/intellij/codeInsight/completion/impl/CamelHumpMatcher.java

@@ -45,7 +45,7 @@ public class CamelHumpMatcher extends PrefixMatcher {
 
   @Override
   public boolean isStartMatch(LookupElement element) {
-    for (String s : CompletionUtil.getImmutableLookupStrings(element)) {
+    for (String s : CompletionUtil.iterateLookupStrings(element)) {
       FList<TextRange> ranges = myCaseInsensitiveMatcher.matchingFragments(s);
       if (ranges == null) continue;
       if (ranges.isEmpty() || skipUnderscores(s) >= ranges.get(0).getStartOffset()) {

platform/lang-impl/src/com/intellij/codeInsight/completion/impl/LiftShorterItemsClassifier.java

@@ -61,7 +61,7 @@ public class LiftShorterItemsClassifier extends Classifier<LookupElement> {
   public void addElement(LookupElement added, ProcessingContext context) {
     myCount++;
 
-    for (String string : CompletionUtil.getImmutableLookupStrings(added)) {
+    for (String string : CompletionUtil.iterateLookupStrings(added)) {
       if (string.length() == 0) continue;
 
       myElements.putValue(string, added);
@@ -97,7 +97,7 @@ public class LiftShorterItemsClassifier extends Classifier<LookupElement> {
 
   private void calculateToLift(LookupElement element) {
     boolean hasChanges = false;
-    for (String string : CompletionUtil.getImmutableLookupStrings(element)) {
+    for (String string : CompletionUtil.iterateLookupStrings(element)) {
       for (int len = 1; len < string.length(); len++) {
         String prefix = string.substring(0, len);
         for (LookupElement shorterElement : myElements.get(prefix)) {