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/*
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (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.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Rhino code, released
* May 6, 1999.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1997-1999
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Bob Jervis
* Google Inc.
*
* Alternatively, the contents of this file may be used under the terms of
* the GNU General Public License Version 2 or later (the "GPL"), in which
* case the provisions of the GPL are applicable instead of those above. If
* you wish to allow use of your version of this file only under the terms of
* the GPL and not to allow others to use your version of this file under the
* MPL, indicate your decision by deleting the provisions above and replacing
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* not delete the provisions above, a recipient may use your version of this
* file under either the MPL or the GPL.
*
* ***** END LICENSE BLOCK ***** */
package com.google.javascript.rhino.jstype;
import com.google.common.collect.Sets;
import com.google.javascript.rhino.jstype.ContainsUpperBoundSuperTypeVisitor.Result;
import java.util.Set;
import javax.annotation.Nullable;
/**
* A type visitor that traverse through the referenced types of "forwaring types" to search for a
* target type.
*
* The result of the visitation indicates whether the target type was present, absent, or
* undcidable due to a cycle.
*
*
This is used by {@link TemplateType} as a helper in cycle detection and subtyping. Cycles are
* checked for once after TemplateTypes are constructed in FunctionTypeBuilder and an error is
* emitted if they are found.
*/
final class ContainsUpperBoundSuperTypeVisitor extends Visitor.WithDefaultCase {
private final JSType target;
private final Set seen = Sets.newIdentityHashSet();
public ContainsUpperBoundSuperTypeVisitor(JSType target) {
this.target = target;
}
@Override
protected Result caseDefault(@Nullable JSType type) {
if (this.target == null) {
return Result.ABSENT;
}
return JSType.areIdentical(type, this.target) ? Result.PRESENT : Result.ABSENT;
}
@Override
public Result caseTemplateType(TemplateType type) {
return caseForwardingType(type, type.getBound());
}
@Override
public Result caseNamedType(NamedType type) {
return caseForwardingType(type, type.getReferencedType());
}
@Override
public Result caseTemplatizedType(TemplatizedType type) {
return caseForwardingType(type, type.getReferencedType());
}
@Override
public Result caseUnionType(UnionType type) {
if (JSType.areIdentical(type, target)) {
return Result.PRESENT;
}
for (JSType alt : type.getAlternates()) {
Result foundInAlt = alt.visit(this);
if (foundInAlt != Result.ABSENT) {
return foundInAlt;
}
}
return Result.ABSENT;
}
private Result caseForwardingType(JSType type, JSType reference) {
if (JSType.areIdentical(type, target)) {
return Result.PRESENT;
} else if (seen.contains(type)) {
return Result.CYCLE;
} else {
seen.add(type);
return reference.visit(this);
}
}
/** Represents the outcome of a visitation of the {@link ContainsUpperBoundSuperTypeVisitor}. */
enum Result {
PRESENT,
ABSENT,
/** Containment is undecidable due to a reference cycle. */
CYCLE;
}
}