com.google.web.bindery.requestfactory.apt.TypeSimplifier Maven / Gradle / Ivy

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Vaadin is a web application framework for Rich Internet Applications (RIA). Vaadin enables easy development and maintenance of fast and secure rich web applications with a stunning look and feel and a wide browser support. It features a server-side architecture with the majority of the logic running on the server. Ajax technology is used at the browser-side to ensure a rich and interactive user experience.

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/*
 * Copyright 2011 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 * 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.web.bindery.requestfactory.apt;

import java.util.ArrayList;
import java.util.List;

import javax.lang.model.element.TypeElement;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.type.NoType;
import javax.lang.model.type.PrimitiveType;
import javax.lang.model.type.TypeKind;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.type.TypeVariable;
import javax.lang.model.type.WildcardType;
import javax.lang.model.util.SimpleTypeVisitor6;

/**
 * Utility type for reducing complex type declarations to ones suitable for
 * determining assignability based on RequestFactory's type-mapping semantics.
 * 
 * Rules:
 * 

 * primitive type {@code ->} boxed type (optional)
 * {@code void -> Void} (optional)
 * {@code  -> Foo}
 * {@code ? extends Foo -> Foo}
 * {@code Foo -> Foo}
 * 
 */
public class TypeSimplifier extends SimpleTypeVisitor6 {

  public static TypeMirror simplify(TypeMirror toBox, boolean boxPrimitives, State state) {
    if (toBox == null) {
      return null;
    }
    return toBox.accept(new TypeSimplifier(boxPrimitives), state);
  }

  private final boolean boxPrimitives;

  private TypeSimplifier(boolean boxPrimitives) {
    this.boxPrimitives = boxPrimitives;
  }

  @Override
  public TypeMirror visitDeclared(DeclaredType x, State state) {
    if (x.getTypeArguments().isEmpty()) {
      return x;
    }
    List newArgs = new ArrayList(x.getTypeArguments().size());
    for (TypeMirror original : x.getTypeArguments()) {
      // Are we looking at a self-parameterized type like Foo>?
      if (original.getKind().equals(TypeKind.TYPEVAR) && state.types.isAssignable(original, x)) {
        // If so, return a raw type
        return state.types.getDeclaredType((TypeElement) x.asElement());
      } else {
        newArgs.add(original.accept(this, state));
      }
    }
    return state.types.getDeclaredType((TypeElement) x.asElement(), newArgs
        .toArray(new TypeMirror[newArgs.size()]));
  }

  @Override
  public TypeMirror visitNoType(NoType x, State state) {
    if (boxPrimitives) {
      return state.findType(Void.class);
    }
    return x;
  }

  @Override
  public TypeMirror visitPrimitive(PrimitiveType x, State state) {
    if (boxPrimitives) {
      return state.types.boxedClass(x).asType();
    }
    return x;
  }

  @Override
  public TypeMirror visitTypeVariable(TypeVariable x, State state) {
    if (x.equals(x.getUpperBound())) {
      // See comment in TransportableTypeVisitor
      return state.types.erasure(x);
    }
    return x.getUpperBound().accept(this, state);
  }

  @Override
  public TypeMirror visitWildcard(WildcardType x, State state) {
    return state.types.erasure(x).accept(this, state);
  }

  @Override
  protected TypeMirror defaultAction(TypeMirror x, State state) {
    return state.types.getNoType(TypeKind.NONE);
  }
}