stub hierarchy: store supers in a more compact form

java/java-impl/src/com/intellij/psi/stubsHierarchy/impl/StubHierarchyConnector.java

@@ -53,34 +53,35 @@ public class StubHierarchyConnector {
       ((Symbol.ClassSymbol)c.myOwner).connect(this);
     }
 
+    Object supers = c.mySuperClasses;
+    if (supers == null) {
+      c.setSupers(Collections.emptySet());
+      return;
+    }
+
     // Determine supertype.
     Set<Symbol.ClassSymbol> supertypes = new HashSet<>();
-    for (QualifiedName name : c.mySuperNames) {
-      try {
-        resolveName(c, name, supertypes);
-      }
-      catch (IncompleteHierarchyException ignore) {
-        c.markHierarchyIncomplete();
-        return;
-      }
-    }
 
-    if (isJavaLangObject(c) || c.isHierarchyIncomplete()) {
-      c.mySuperClasses = Symbol.ClassSymbol.EMPTY_ARRAY;
-    } else {
-      for (Iterator<Symbol.ClassSymbol> iter = supertypes.iterator(); iter.hasNext();) {
-        Symbol.ClassSymbol s = iter.next();
-        if (isJavaLangObject(s)) {
-            iter.remove();
+    try {
+      if (supers instanceof QualifiedName[]) {
+        for (QualifiedName name : (QualifiedName[])supers) {
+          resolveName(c, name, supertypes);
         }
+      } else {
+        resolveName(c, (QualifiedName)supers, supertypes);
       }
-      c.mySuperClasses =
-        supertypes.isEmpty() ? Symbol.ClassSymbol.EMPTY_ARRAY : supertypes.toArray(new Symbol.ClassSymbol[supertypes.size()]);
+    }
+    catch (IncompleteHierarchyException ignore) {
+      c.markHierarchyIncomplete();
+      return;
     }
 
-    // cleaning up
-    c.mySuperNames = null;
-    c.myUnitInfo = null;
+    for (Iterator<Symbol.ClassSymbol> iterator = supertypes.iterator(); iterator.hasNext();) {
+      if (isJavaLangObject(iterator.next())) {
+        iterator.remove();
+      }
+    }
+    c.setSupers(supertypes);
   }
 
   private boolean isJavaLangObject(Symbol s) {

java/java-impl/src/com/intellij/psi/stubsHierarchy/impl/Symbol.java

@@ -21,7 +21,9 @@ import com.intellij.util.BitUtil;
 import gnu.trove.TIntHashSet;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.Collections;
 import java.util.Comparator;
+import java.util.Set;
 
 /**
  * Java symbols needed for hierarchy building. Mostly classes ({@link ClassSymbol}) or packages ({@link PackageSymbol}),
@@ -88,9 +90,14 @@ public abstract class Symbol {
     public static final ClassSymbol[] EMPTY_ARRAY = new ClassSymbol[0];
 
     final StubClassAnchor myClassAnchor;
-    ClassSymbol[] mySuperClasses;
+
+    /**
+     * null for empty 'supers' list
+     * ClassSymbol/QualifiedName for a single resolved/unresolved super
+     * ClassSymbol[]/QualifiedName[] for multiple resolved/unresolved supers
+     */
+    Object mySuperClasses;
     UnitInfo myUnitInfo;
-    QualifiedName[] mySuperNames;
     private ClassSymbol[] myMembers;
 
     ClassSymbol(StubClassAnchor classAnchor,
@@ -101,7 +108,7 @@ public abstract class Symbol {
                 QualifiedName[] supers) {
       super(flags | IndexTree.CLASS, owner, name);
       this.myClassAnchor = classAnchor;
-      this.mySuperNames = supers;
+      this.mySuperClasses = supers.length == 0 ? null : supers.length == 1 ? supers[0] : supers;
       this.myUnitInfo = unitInfo;
     }
 
@@ -133,7 +140,9 @@ public abstract class Symbol {
     @NotNull
     ClassSymbol[] rawSuperClasses() {
       assert isConnectStarted();
-      return mySuperClasses == null ? EMPTY_ARRAY : mySuperClasses;
+      return mySuperClasses instanceof ClassSymbol ? new ClassSymbol[]{(ClassSymbol)mySuperClasses} :
+             mySuperClasses instanceof ClassSymbol[] ? (ClassSymbol[])mySuperClasses :
+             EMPTY_ARRAY;
     }
 
     boolean isCompiled() {
@@ -149,12 +158,17 @@ public abstract class Symbol {
     }
 
     void markHierarchyIncomplete() {
-      mySuperClasses = EMPTY_ARRAY;
-      mySuperNames = null;
-      myUnitInfo = null;
+      setSupers(Collections.emptySet());
       myFlags = BitUtil.set(myFlags, HIERARCHY_INCOMPLETE, true);
     }
 
+    void setSupers(Set<ClassSymbol> supers) {
+      mySuperClasses = supers.isEmpty() ? null :
+                       supers.size() == 1 ? supers.iterator().next() :
+                       supers.toArray(new ClassSymbol[supers.size()]);
+      myUnitInfo = null;
+    }
+
     boolean isHierarchyIncomplete() {
       return BitUtil.isSet(myFlags, HIERARCHY_INCOMPLETE);
     }