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Groovy: A powerful multi-faceted language for the JVM
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.codehaus.groovy.control;
import org.codehaus.groovy.ast.ClassCodeVisitorSupport;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.FieldNode;
import org.codehaus.groovy.ast.GenericsType;
import org.codehaus.groovy.ast.InnerClassNode;
import org.codehaus.groovy.ast.MethodNode;
import org.codehaus.groovy.ast.Parameter;
import org.codehaus.groovy.ast.expr.ArrayExpression;
import org.codehaus.groovy.ast.expr.CastExpression;
import org.codehaus.groovy.ast.expr.ConstructorCallExpression;
import org.codehaus.groovy.ast.expr.DeclarationExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.VariableExpression;
import org.codehaus.groovy.transform.trait.Traits;
import static org.codehaus.groovy.transform.stc.StaticTypeCheckingSupport.isUnboundedWildcard;
/**
* Verify correct usage of generics.
* This includes:
*
* - class header (class and superclass declaration)
* - arity of type parameters for fields, parameters, local variables
* - invalid diamond {@code <>} usage
*
*/
public class GenericsVisitor extends ClassCodeVisitorSupport {
private final SourceUnit source;
@Override
protected SourceUnit getSourceUnit() {
return source;
}
public GenericsVisitor(final SourceUnit source) {
this.source = source;
}
//--------------------------------------------------------------------------
@Override
public void visitClass(final ClassNode node) {
ClassNode sc = node.getUnresolvedSuperClass(false);
if (checkWildcard(sc)) return;
boolean isAIC = node instanceof InnerClassNode && ((InnerClassNode) node).isAnonymous();
checkGenericsUsage(sc, sc.redirect(), isAIC ? Boolean.TRUE : null);
for (ClassNode face : node.getInterfaces()) {
checkGenericsUsage(face);
}
visitObjectInitializerStatements(node);
node.visitContents(this);
}
@Override
public void visitField(final FieldNode node) {
checkGenericsUsage(node.getType());
super.visitField(node);
}
@Override
protected void visitConstructorOrMethod(final MethodNode node, final boolean isConstructor) {
for (Parameter p : node.getParameters()) {
checkGenericsUsage(p.getType());
}
if (!isConstructor) {
checkGenericsUsage(node.getReturnType());
}
super.visitConstructorOrMethod(node, isConstructor);
}
@Override
public void visitConstructorCallExpression(final ConstructorCallExpression expression) {
ClassNode type = expression.getType();
boolean isAIC = type instanceof InnerClassNode
&& ((InnerClassNode) type).isAnonymous();
checkGenericsUsage(type, type.redirect(), isAIC);
super.visitConstructorCallExpression(expression);
}
@Override
public void visitDeclarationExpression(final DeclarationExpression expression) {
if (expression.isMultipleAssignmentDeclaration()) {
for (Expression e : expression.getTupleExpression().getExpressions()) {
checkGenericsUsage(((VariableExpression) e).getOriginType());
}
} else {
checkGenericsUsage(expression.getVariableExpression().getOriginType());
}
super.visitDeclarationExpression(expression);
}
@Override
public void visitArrayExpression(final ArrayExpression expression) {
checkGenericsUsage(expression.getType());
super.visitArrayExpression(expression);
}
@Override
public void visitCastExpression(final CastExpression expression) {
checkGenericsUsage(expression.getType());
super.visitCastExpression(expression);
}
//--------------------------------------------------------------------------
private boolean checkWildcard(final ClassNode sn) {
boolean wildcard = false;
if (sn.getGenericsTypes() != null) {
for (GenericsType gt : sn.getGenericsTypes()) {
if (gt.isWildcard()) {
addError("A supertype may not specify a wildcard type", sn);
wildcard = true;
}
}
}
return wildcard;
}
private void checkGenericsUsage(ClassNode cn) {
while (cn.isArray())
cn = cn.getComponentType();
checkGenericsUsage(cn, cn.redirect(), null);
}
private void checkGenericsUsage(final ClassNode cn, final ClassNode rn, final Boolean isAIC) {
if (cn.isGenericsPlaceHolder()) return;
GenericsType[] cnTypes = cn.getGenericsTypes();
// raw type usage is always allowed
if (cnTypes == null) return;
GenericsType[] rnTypes = rn.getGenericsTypes();
// you can't parameterize a non-generified type
if (rnTypes == null) {
String message = "The class " + cn.toString(false) + " (supplied with " + plural("type parameter", cnTypes.length) +
") refers to the class " + rn.toString(false) + " which takes no parameters";
if (cnTypes.length == 0) {
message += " (invalid Diamond <> usage?)";
}
addError(message, cn);
return;
}
// parameterize a type by using all the parameters only
if (cnTypes.length != rnTypes.length) {
if (Boolean.FALSE.equals(isAIC) && cnTypes.length == 0) {
return; // allow Diamond for non-AIC cases from CCE
}
String message;
if (Boolean.TRUE.equals(isAIC) && cnTypes.length == 0) {
message = "Cannot use diamond <> with anonymous inner classes";
} else {
message = "The class " + cn.toString(false) + " (supplied with " + plural("type parameter", cnTypes.length) +
") refers to the class " + rn.toString(false) + " which takes " + plural("parameter", rnTypes.length);
if (cnTypes.length == 0) {
message += " (invalid Diamond <> usage?)";
}
}
addError(message, cn);
return;
}
for (int i = 0; i < cnTypes.length; i++) {
ClassNode cnType = cnTypes[i].getType();
ClassNode rnType = rnTypes[i].getType();
// check nested type parameters
checkGenericsUsage(cnType);
// check bounds: unbounded wildcard (aka "?") is universal substitute
if (!isUnboundedWildcard(cnTypes[i])) {
// check upper bound(s)
ClassNode[] bounds = rnTypes[i].getUpperBounds();
// first can be class or interface
boolean valid = cnType.isDerivedFrom(rnType) || ((rnType.isInterface() || Traits.isTrait(rnType)) && cnType.implementsInterface(rnType));
// subsequent bounds if present can be interfaces
if (valid && bounds != null && bounds.length > 1) {
for (int j = 1; j < bounds.length; j++) {
ClassNode bound = bounds[j];
if (!cnType.implementsInterface(bound)) {
valid = false;
break;
}
}
}
if (!valid) {
addError("The type " + cnTypes[i].getName() + " is not a valid substitute for the bounded parameter <" + rnTypes[i] + ">", cnTypes[i]);
}
}
}
}
private static String plural(final String string, final int count) {
return "" + count + " " + (count == 1 ? string : string + "s");
}
}