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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2019 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp.disambiguate;

import com.google.javascript.jscomp.graph.FixedPointGraphTraversal;

/** A callback to propagate clusterings across a type graph. */
final class ClusterPropagator implements FixedPointGraphTraversal.EdgeCallback {

  ClusterPropagator() {}

  @Override
  public boolean traverseEdge(FlatType src, Object unused, FlatType dest) {
    int startDestPropCount = dest.getAssociatedProps().size();

    /**
     * We make sure to check invalidation on the source first to preempt property propagation.
     * There's no point in porpagating any properties in that case. Clearing them eagerly saves time
     * and memory.
     */
    invalidatePropertiesIfInvalidating(src);

    for (PropertyClustering prop : src.getAssociatedProps()) {
      if (prop.isInvalidated()) {
        continue;
      }

      dest.getAssociatedProps().add(prop);
      prop.getClusters().union(src, dest);
    }

    invalidatePropertiesIfInvalidating(dest);

    // Were any properties added to dest?
    return startDestPropCount < dest.getAssociatedProps().size();
  }

  private static void invalidatePropertiesIfInvalidating(FlatType flat) {
    if (flat.isInvalidating()) {
      flat.getAssociatedProps().forEach(PropertyClustering::invalidate);
      flat.getAssociatedProps().clear();
    }
  }
}