Issue 5157. Introduce TypeQuality. Try to find member in subclasses.

compiler/java/com/google/dart/compiler/type/InterfaceTypeImplementation.java

Index: compiler/java/com/google/dart/compiler/type/InterfaceTypeImplementation.java
diff --git a/compiler/java/com/google/dart/compiler/type/InterfaceTypeImplementation.java b/compiler/java/com/google/dart/compiler/type/InterfaceTypeImplementation.java
index a7ab8d64ab094c2dfa186ad53fc4e5eef1289e30..fac151a68bf2889a326fc71679b8e1bc3582d9d6 100644
--- a/compiler/java/com/google/dart/compiler/type/InterfaceTypeImplementation.java
+++ b/compiler/java/com/google/dart/compiler/type/InterfaceTypeImplementation.java
@@ -4,6 +4,7 @@
 
 package com.google.dart.compiler.type;
 
+import com.google.common.collect.MapMaker;
 import com.google.dart.compiler.resolver.ClassElement;
 import com.google.dart.compiler.resolver.Element;
 import com.google.dart.compiler.resolver.ElementKind;
@@ -15,6 +16,7 @@ import com.google.dart.compiler.util.apache.StringUtils;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 
 /**
  * An interface type.
@@ -22,6 +24,7 @@ import java.util.List;
 class InterfaceTypeImplementation extends AbstractType implements InterfaceType {
   private final ClassElement element;
   private final List<Type> arguments;
+  private final Map<ClassElement, Object> subClasses = new MapMaker().weakKeys().makeMap();
 
   InterfaceTypeImplementation(ClassElement element, List<Type> arguments) {
     this.element = element;
@@ -217,4 +220,34 @@ class InterfaceTypeImplementation extends AbstractType implements InterfaceType
       return getterType.subst(typeArguments, typeParameters);
     }
   }
+  
+  @Override
+  public void registerSubClass(ClassElement subClass) {
+    subClasses.put(subClass, this);
+  }
+  
+  @Override
+  public void unregisterSubClass(ClassElement subClass) {
+    subClasses.remove(subClass);
+  }
+  
+  @Override
+  public Member lookupSubTypeMember(String name) {
+    for (ClassElement subClass : subClasses.keySet()) {
+      {
+        Element element = subClass.lookupLocalElement(name);
+        if (element != null) {
+          return new MemberImplementation(this, element);
+        }
+      }
+      InterfaceType type = subClass.getType();
+      if (type != null) {
+        Member member = type.lookupSubTypeMember(name);
+        if (member != null) {
+          return member;
+        }
+      }
+    }
+    return null;
+  }
 }