diff --git a/platform/analysis-api/src/com/intellij/psi/search/GlobalSearchScopesCore.java b/platform/analysis-api/src/com/intellij/psi/search/GlobalSearchScopesCore.java
index ffea51b3e79b..072e12114bc6 100644
--- a/platform/analysis-api/src/com/intellij/psi/search/GlobalSearchScopesCore.java
+++ b/platform/analysis-api/src/com/intellij/psi/search/GlobalSearchScopesCore.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2013 JetBrains s.r.o.
+ * Copyright 2000-2014 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,8 +26,14 @@ import com.intellij.psi.PsiDirectory;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.PsiManager;
 import com.intellij.psi.search.scope.packageSet.*;
+import com.intellij.util.ArrayUtil;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.BitSet;
+import java.util.List;
+
 public class GlobalSearchScopesCore {
   @NotNull
   public static GlobalSearchScope projectProductionScope(@NotNull Project project) {
@@ -216,5 +222,131 @@ public class GlobalSearchScopesCore {
       //noinspection HardCodedStringLiteral
       return "directory scope: " + myDirectory + "; withSubdirs:"+myWithSubdirectories;
     }
+
+    @Override
+    public int hashCode() {
+      return myDirectory.hashCode() *31 + (myWithSubdirectories?1:0);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      return obj instanceof DirectoryScope &&
+             myDirectory.equals(((DirectoryScope)obj).myDirectory) &&
+             myWithSubdirectories == ((DirectoryScope)obj).myWithSubdirectories;
+    }
+
+    @NotNull
+    @Override
+    public GlobalSearchScope uniteWith(@NotNull GlobalSearchScope scope) {
+      if (equals(scope)) return this;
+      if (scope instanceof DirectoryScope) {
+        DirectoryScope other = (DirectoryScope)scope;
+        VirtualFile otherDirectory = other.myDirectory;
+        if (myWithSubdirectories && VfsUtilCore.isAncestor(myDirectory, otherDirectory, false)) return this;
+        if (other.myWithSubdirectories && VfsUtilCore.isAncestor(otherDirectory, myDirectory, false)) return other;
+        BitSet newWithSubdirectories = new BitSet();
+        newWithSubdirectories.set(0, myWithSubdirectories);
+        newWithSubdirectories.set(1, other.myWithSubdirectories);
+        return new DirectoriesScope(getProject(), new VirtualFile[]{myDirectory,otherDirectory}, newWithSubdirectories);
+      }
+      return super.uniteWith(scope);
+    }
+  }
+
+  static class DirectoriesScope extends GlobalSearchScope {
+    private final VirtualFile[] myDirectories;
+    private final BitSet myWithSubdirectories;
+
+    private DirectoriesScope(@NotNull Project project, @NotNull VirtualFile[] directories, @NotNull BitSet withSubdirectories) {
+      super(project);
+      myWithSubdirectories = withSubdirectories;
+      myDirectories = directories;
+    }
+
+    @Override
+    public boolean contains(@NotNull VirtualFile file) {
+      VirtualFile parent = file.getParent();
+      return parent != null && in(parent);
+    }
+
+    private boolean in(@NotNull VirtualFile parent) {
+      for (int i = 0; i < myDirectories.length; i++) {
+        VirtualFile directory = myDirectories[i];
+        boolean withSubdirectories = myWithSubdirectories.get(i);
+        if (withSubdirectories ? VfsUtilCore.isAncestor(directory, parent, false) : directory.equals(parent)) return true;
+      }
+      return false;
+    }
+
+    @Override
+    public int compare(@NotNull VirtualFile file1, @NotNull VirtualFile file2) {
+      return 0;
+    }
+
+    @Override
+    public boolean isSearchInModuleContent(@NotNull Module aModule) {
+      return true;
+    }
+
+    @Override
+    public boolean isSearchInLibraries() {
+      return false;
+    }
+
+    public String toString() {
+      //noinspection HardCodedStringLiteral
+      return "Directories scope: " + Arrays.asList(myDirectories);
+    }
+
+    @Override
+    public int hashCode() {
+      int result = 1;
+      for (int i = 0; i < myDirectories.length; i++) {
+        VirtualFile directory = myDirectories[i];
+        boolean withSubdirectories = myWithSubdirectories.get(i);
+        result = result*31 + directory.hashCode() *31 + (withSubdirectories?1:0);
+      }
+      return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      return obj instanceof DirectoriesScope &&
+             Arrays.equals(myDirectories, ((DirectoriesScope)obj).myDirectories) &&
+             myWithSubdirectories.equals(((DirectoriesScope)obj).myWithSubdirectories);
+    }
+
+    @NotNull
+    @Override
+    public GlobalSearchScope uniteWith(@NotNull GlobalSearchScope scope) {
+      if (equals(scope)) {
+        return this;
+      }
+      if (scope instanceof DirectoryScope) {
+        if (in(((DirectoryScope)scope).myDirectory)) {
+          return this;
+        }
+        VirtualFile[] newDirectories = ArrayUtil.append(myDirectories, ((DirectoryScope)scope).myDirectory, VirtualFile.class);
+        BitSet newWithSubdirectories = (BitSet)myWithSubdirectories.clone();
+        newWithSubdirectories.set(myDirectories.length, ((DirectoryScope)scope).myWithSubdirectories);
+        return new DirectoriesScope(getProject(), newDirectories, newWithSubdirectories);
+      }
+      if (scope instanceof DirectoriesScope) {
+        DirectoriesScope other = (DirectoriesScope)scope;
+        List<VirtualFile> newDirectories = new ArrayList<VirtualFile>(myDirectories.length + other.myDirectories.length);
+        newDirectories.addAll(Arrays.asList(other.myDirectories));
+        BitSet newWithSubdirectories = (BitSet)myWithSubdirectories.clone();
+        VirtualFile[] directories = other.myDirectories;
+        for (int i = 0; i < directories.length; i++) {
+          VirtualFile otherDirectory = directories[i];
+          if (!in(otherDirectory)) {
+            newWithSubdirectories.set(newDirectories.size(), other.myWithSubdirectories.get(i));
+            newDirectories.add(otherDirectory);
+          }
+        }
+        return new DirectoriesScope(getProject(), newDirectories.toArray(new VirtualFile[newDirectories.size()]), newWithSubdirectories);
+      }
+      return super.uniteWith(scope);
+    }
   }
 }
diff --git a/platform/platform-tests/testSrc/com/intellij/psi/search/GlobalSearchScopeTest.java b/platform/platform-tests/testSrc/com/intellij/psi/search/GlobalSearchScopeTest.java
new file mode 100644
index 000000000000..418190f427b6
--- /dev/null
+++ b/platform/platform-tests/testSrc/com/intellij/psi/search/GlobalSearchScopeTest.java
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2000-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.psi.search;
+
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.testFramework.PlatformTestCase;
+
+public class GlobalSearchScopeTest extends PlatformTestCase {
+  public void testUniteDirectorySearchScopeDoesNotSOE() throws Exception {
+    VirtualFile genRoot = getVirtualFile(createTempDir("genSrcRoot"));
+    VirtualFile srcRoot = getVirtualFile(createTempDir("srcRoot"));
+    VirtualFile child = srcRoot.createChildDirectory(this, "child");
+    GlobalSearchScope childScope = GlobalSearchScopesCore.directoryScope(getProject(), child, true);
+
+    GlobalSearchScope directoryScope = GlobalSearchScopesCore.directoryScope(getProject(), srcRoot, true);
+    GlobalSearchScope scope = GlobalSearchScope.EMPTY_SCOPE.uniteWith(directoryScope);
+    assertSame(scope, directoryScope);
+    scope = scope.uniteWith(directoryScope);
+    assertSame(scope, directoryScope);
+
+    scope = scope.uniteWith(childScope);
+    assertSame(scope, directoryScope);
+
+    GlobalSearchScope s = childScope;
+    int N = 1000;
+    VirtualFile[] d = new VirtualFile[N];
+    for (int i=0; i< N;i++) {
+      d[i] = srcRoot.createChildDirectory(this, "d"+i);
+      GlobalSearchScope united = s.uniteWith(GlobalSearchScopesCore.directoryScope(getProject(), d[i], true));
+      assertNotSame(s, united);
+      s = united;
+      assertTrue(s instanceof GlobalSearchScopesCore.DirectoriesScope);
+    }
+    for (VirtualFile file : d) {
+      VirtualFile f = createChildData(file, "f");
+      assertTrue(s.contains(f));
+    }
+    assertFalse(s.contains(genRoot));
+
+    assertSame(s.uniteWith(childScope), s);
+    assertSame(s.uniteWith(s), s);
+  }
+}
\ No newline at end of file
diff --git a/platform/util/src/com/intellij/util/ArrayUtil.java b/platform/util/src/com/intellij/util/ArrayUtil.java
index 1e47adf8fcf1..5de68c11799b 100644
--- a/platform/util/src/com/intellij/util/ArrayUtil.java
+++ b/platform/util/src/com/intellij/util/ArrayUtil.java
@@ -78,6 +78,21 @@ public class ArrayUtil extends ArrayUtilRt {
     System.arraycopy(array, 0, result, 0, Math.min(oldSize, newSize));
     return result;
   }
+  @NotNull
+  public static boolean[] realloc(@NotNull boolean[] array, final int newSize) {
+    if (newSize == 0) {
+      return EMPTY_BOOLEAN_ARRAY;
+    }
+
+    final int oldSize = array.length;
+    if (oldSize == newSize) {
+      return array;
+    }
+
+    boolean[] result = new boolean[newSize];
+    System.arraycopy(array, 0, result, 0, Math.min(oldSize, newSize));
+    return result;
+  }
 
   @NotNull
   public static int[] realloc(@NotNull int[] array, final int newSize) {
@@ -131,6 +146,12 @@ public class ArrayUtil extends ArrayUtilRt {
     array[array.length - 1] = value;
     return array;
   }
+  @NotNull
+  public static boolean[] append(@NotNull boolean[] array, boolean value) {
+    array = realloc(array, array.length + 1);
+    array[array.length - 1] = value;
+    return array;
+  }
 
   @NotNull
   public static char[] realloc(@NotNull char[] array, final int newSize) {