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/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* 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.turbine.binder.lookup;
import static com.google.common.base.Preconditions.checkNotNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/** A {@link Scope} that chains other scopes together. */
public class CompoundScope implements Scope {
private final Scope scope;
private final @Nullable Scope base;
private CompoundScope(Scope scope, @Nullable Scope base) {
this.scope = checkNotNull(scope);
this.base = base;
}
@Override
public @Nullable LookupResult lookup(LookupKey key) {
LookupResult result = scope.lookup(key);
if (result != null) {
return result;
}
if (base != null) {
return base.lookup(key);
}
return null;
}
/** Adds a scope to the chain. */
public CompoundScope append(Scope scope) {
return new CompoundScope(scope, this);
}
/** A chainable compound scope with a single entry. */
public static CompoundScope base(Scope scope) {
return new CompoundScope(scope, null);
}
}
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