From 0d7a641aa9642ccf4b745f496d9e441c4ae61aa8 Mon Sep 17 00:00:00 2001
From: Dmitry Jemerov <yole@jetbrains.com>
Date: Thu, 15 Dec 2011 18:35:48 +0100
Subject: [PATCH] lazily calculate control flow in ScopeImpl

---
 .../dataflow/scope/impl/ScopeImpl.java            | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/python/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java b/python/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java
index 3a2d2da2ff73..b4fff8178244 100644
--- a/python/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java
+++ b/python/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java
@@ -23,8 +23,8 @@ import java.util.*;
  * @author oleg
  */
 public class ScopeImpl implements Scope {
-  private final Instruction[] myFlow;
-  private List<DFAMap<ScopeVariable>> myCachedScopeVariables;
+  private volatile Instruction[] myFlow;
+  private volatile List<DFAMap<ScopeVariable>> myCachedScopeVariables;
   private Set<String> myGlobals;
   private Set<String> myNonlocals;
   private final ScopeOwner myFlowOwner;
@@ -33,7 +33,12 @@ public class ScopeImpl implements Scope {
 
   public ScopeImpl(final ScopeOwner flowOwner) {
     myFlowOwner = flowOwner;
-    myFlow = ControlFlowCache.getControlFlow(flowOwner).getInstructions();
+  }
+
+  private synchronized void computeFlow() {
+    if (myFlow == null) {
+      myFlow = ControlFlowCache.getControlFlow(myFlowOwner).getInstructions();
+    }
   }
 
   @NotNull
@@ -62,7 +67,8 @@ public class ScopeImpl implements Scope {
     return null;
   }
 
-  public List<DFAMap<ScopeVariable>> computeScopeVariables() throws DFALimitExceededException {
+  private synchronized List<DFAMap<ScopeVariable>> computeScopeVariables() throws DFALimitExceededException {
+    computeFlow();
     if (myCachedScopeVariables == null) {
       final PyReachingDefsDfaInstance dfaInstance = new PyReachingDefsDfaInstance();
       final PyReachingDefsSemilattice semilattice = new PyReachingDefsSemilattice();
@@ -104,6 +110,7 @@ public class ScopeImpl implements Scope {
   }
 
   private Set<String> computeAllNames() {
+    computeFlow();
     final Set<String> names = new HashSet<String>();
     for (Instruction instruction : myFlow) {
       if (instruction instanceof ReadWriteInstruction && ((ReadWriteInstruction)instruction).getAccess().isWriteAccess()){