Show an error if a field has no getter defined in a getter context

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

Index: compiler/java/com/google/dart/compiler/resolver/Elements.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/Elements.java b/compiler/java/com/google/dart/compiler/resolver/Elements.java
index de927822556fcda1c2f7096b4acd15f37e2e15f6..9acdb69a76bd21fe091fce04854ae38733fdbec7 100644
--- a/compiler/java/com/google/dart/compiler/resolver/Elements.java
+++ b/compiler/java/com/google/dart/compiler/resolver/Elements.java
@@ -6,10 +6,13 @@ package com.google.dart.compiler.resolver;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Objects;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import com.google.dart.compiler.DartSource;
 import com.google.dart.compiler.LibrarySource;
 import com.google.dart.compiler.Source;
+import com.google.dart.compiler.ast.DartBinaryExpression;
 import com.google.dart.compiler.ast.DartClass;
 import com.google.dart.compiler.ast.DartClassMember;
 import com.google.dart.compiler.ast.DartField;
@@ -21,6 +24,7 @@ import com.google.dart.compiler.ast.DartMethodDefinition;
 import com.google.dart.compiler.ast.DartNativeBlock;
 import com.google.dart.compiler.ast.DartNode;
 import com.google.dart.compiler.ast.DartParameter;
+import com.google.dart.compiler.ast.DartPropertyAccess;
 import com.google.dart.compiler.ast.DartSuperExpression;
 import com.google.dart.compiler.ast.DartTypeNode;
 import com.google.dart.compiler.ast.DartTypeParameter;
@@ -28,6 +32,7 @@ import com.google.dart.compiler.ast.DartVariable;
 import com.google.dart.compiler.ast.LibraryUnit;
 import com.google.dart.compiler.ast.Modifiers;
 import com.google.dart.compiler.common.SourceInfo;
+import com.google.dart.compiler.parser.Token;
 import com.google.dart.compiler.type.InterfaceType;
 import com.google.dart.compiler.type.Type;
 import com.google.dart.compiler.type.TypeVariable;
@@ -44,6 +49,21 @@ import java.util.Set;
  * Utility and factory methods for elements.
  */
 public class Elements {
+  private static final ImmutableSet<Token> ASSIGN_OPERATORS =
+      Sets.immutableEnumSet(
+          Token.ASSIGN,
+          Token.ASSIGN_BIT_OR,
+          Token.ASSIGN_BIT_XOR,
+          Token.ASSIGN_BIT_AND,
+          Token.ASSIGN_SHL,
+          Token.ASSIGN_SAR,
+          Token.ASSIGN_ADD,
+          Token.ASSIGN_SUB,
+          Token.ASSIGN_MUL,
+          Token.ASSIGN_DIV,
+          Token.ASSIGN_MOD,
+          Token.ASSIGN_TRUNC);
+  
   private Elements() {} // Prevent subclassing and instantiation.
 
   static void setParameterInitializerElement(VariableElement varElement, FieldElement element) {
@@ -578,4 +598,39 @@ static FieldElementImplementation fieldFromNode(DartField node,
     }
     return false;
   }
+  
+  /**
+   * Looks to see if the property access requires a getter.
+   * 
+   * A property access requires a getter if it is on the right hand side of an assignment,
+   * or if it is on the left hand side of an assignment and uses one of the assignment 
+   * operators other than plain '='.
+   */
+  public static boolean inGetterContext(DartPropertyAccess node) {
+    if (node.getParent() instanceof DartBinaryExpression) {
+      DartBinaryExpression expr = (DartBinaryExpression) node.getParent();
+      if (Token.ASSIGN.equals(expr.getOperator()) && expr.getArg1() == node) {
+        return false;
+      }
+    }
+    return true;    
+  }
+  
+  /**
+   * Looks to see if the property access requires a setter.
+   * 
+   * Basically, this boils down to any property access on the left hand side of an assignment.
+   * 
+   * Keep in mind that an assignment of the form node = <expr> is the only kind of write-only 
+   * expression. Other types of assignments also read the value and require a getter access.
+   */
+  public static boolean inSetterContext(DartNode node) {
+    if (node.getParent() instanceof DartBinaryExpression) {
+      DartBinaryExpression expr = (DartBinaryExpression) node.getParent();
+      if (ASSIGN_OPERATORS.contains(expr.getOperator()) && expr.getArg1() == node) {
+        return true;
+      }
+    }
+    return false;
+  }
 }