Issue 2382. Using a variable in a scope before its declared that shadows another variable

compiler/java/com/google/dart/compiler/resolver/Scope.java

Index: compiler/java/com/google/dart/compiler/resolver/Scope.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/Scope.java b/compiler/java/com/google/dart/compiler/resolver/Scope.java
index ae4fd3c6193e527f666f6ca85e49d4d6fd5da523..fe8d9d6b4ba60141b81aac65e04099ba5fb8886c 100644
--- a/compiler/java/com/google/dart/compiler/resolver/Scope.java
+++ b/compiler/java/com/google/dart/compiler/resolver/Scope.java
@@ -5,12 +5,16 @@
 package com.google.dart.compiler.resolver;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.Sets;
+import com.google.dart.compiler.ast.DartBlock;
 import com.google.dart.compiler.ast.DartIdentifier;
+import com.google.dart.compiler.ast.DartVariableStatement;
 
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 /**
  * A scope used by {@link Resolver}.
@@ -18,6 +22,7 @@ import java.util.Map;
 public class Scope {
 
   private final Map<String, Element> elements = new LinkedHashMap<String, Element>();
+  private final Set<String> declaredButNotReachedVariables = Sets.newHashSet();
   private final Scope parent;
   private final String name;
   private List<LabelElement> labels;
@@ -86,6 +91,29 @@ public class Scope {
   public Map<String, Element> getElements() {
     return elements;
   }
+  
+  /**
+   * @return <code>true</code> if local variable with given name is declared in the lexical context
+   *         of {@link DartBlock}, but corresponding {@link DartVariableStatement} is not visited
+   *         yet. So, using this variable is error.
+   */
+  public boolean isDeclaredButNotReachedVariable(String name) {
+    return declaredButNotReachedVariables.contains(name);
+  }
+  
+  /**
+   * @see #isDeclaredButNotReachedVariable(String)
+   */
+  public void addDeclaredButNotReachedVariable(String name) {
+    declaredButNotReachedVariables.add(name);
+  }
+  
+  /**
+   * @see #isDeclaredButNotReachedVariable(String)
+   */
+  public void removeDeclaredButNotReachedVariable(String name) {
+    declaredButNotReachedVariables.remove(name);
+  }
 
   public String getName() {
     return name;