Issue 13807. Support for type promotion rules.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/TypePromotionManager.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/TypePromotionManager.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/TypePromotionManager.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/TypePromotionManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..620da0cd472bdc139969f8e9cabbb1d2f00716c6
--- /dev/null
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/TypePromotionManager.java
@@ -0,0 +1,152 @@
+/*
+ * Copyright (c) 2013, the Dart project authors.
+ * 
+ * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ * 
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.dart.engine.internal.resolver;
+
+import com.google.dart.engine.element.Element;
+import com.google.dart.engine.element.PropertyAccessorElement;
+import com.google.dart.engine.type.Type;
+
+import java.util.Collection;
+import java.util.HashMap;
+
+/**
+ * Instances of the class {@code TypePromotionManager} manage the ability to promote types of local
+ * variables and formal parameters from their declared types based on control flow.
+ */
+public class TypePromotionManager {
+  /**
+   * Instances of the class {@code TypePromoteScope} represent a scope in which the types of
+   * elements can be promoted.
+   */
+  private static class TypePromoteScope {
+    /**
+     * The outer scope in which types might be promoter.
+     */
+    private TypePromoteScope outerScope;
+
+    /**
+     * A table mapping elements to the promoted type of that element.
+     */
+    private HashMap<Element, Type> promotedTypes = new HashMap<Element, Type>();
+
+    /**
+     * Initialize a newly created scope to be an empty child of the given scope.
+     * 
+     * @param outerScope the outer scope in which types might be promoted
+     */
+    public TypePromoteScope(TypePromoteScope outerScope) {
+      this.outerScope = outerScope;
+    }
+
+    /**
+     * Returns the elements with promoted types.
+     */
+    public Collection<Element> getPromotedElements() {
+      return promotedTypes.keySet();
+    }
+
+    /**
+     * Return the promoted type of the given element, or {@code null} if the type of the element has
+     * not been promoted.
+     * 
+     * @param element the element whose type might have been promoted
+     * @return the promoted type of the given element
+     */
+    public Type getType(Element element) {
+      Type type = promotedTypes.get(element);
+      if (type == null && element instanceof PropertyAccessorElement) {
+        type = promotedTypes.get(((PropertyAccessorElement) element).getVariable());
+      }
+      if (type != null) {
+        return type;
+      } else if (outerScope != null) {
+        return outerScope.getType(element);
+      }
+      return null;
+    }
+
+    /**
+     * Set the promoted type of the given element to the given type.
+     * 
+     * @param element the element whose type might have been promoted
+     * @param type the promoted type of the given element
+     */
+    public void setType(Element element, Type type) {
+      promotedTypes.put(element, type);
+    }
+  }
+
+  /**
+   * The current promotion scope, or {@code null} if no scope has been entered.
+   */
+  private TypePromoteScope currentScope;
+
+  /**
+   * Initialize a newly created promotion manager to not be in any scope.
+   */
+  public TypePromotionManager() {
+    super();
+  }
+
+  /**
+   * Enter a new promotions scope.
+   */
+  public void enterScope() {
+    currentScope = new TypePromoteScope(currentScope);
+  }
+
+  /**
+   * Exit the current promotion scope.
+   */
+  public void exitScope() {
+    if (currentScope == null) {
+      throw new IllegalStateException("No scope to exit");
+    }
+    currentScope = currentScope.outerScope;
+  }
+
+  /**
+   * Returns the elements with promoted types.
+   */
+  public Collection<Element> getPromotedElements() {
+    return currentScope.getPromotedElements();
+  }
+
+  /**
+   * Return the promoted type of the given element, or {@code null} if the type of the element has
+   * not been promoted.
+   * 
+   * @param element the element whose type might have been promoted
+   * @return the promoted type of the given element
+   */
+  public Type getType(Element element) {
+    if (currentScope == null) {
+      return null;
+    }
+    return currentScope.getType(element);
+  }
+
+  /**
+   * Set the promoted type of the given element to the given type.
+   * 
+   * @param element the element whose type might have been promoted
+   * @param type the promoted type of the given element
+   */
+  public void setType(Element element, Type type) {
+    if (currentScope == null) {
+      throw new IllegalStateException("Cannot promote without a scope");
+    }
+    currentScope.setType(element, type);
+  }
+}