checker/src/main/java/org/checkerframework/checker/index/searchindex/SearchIndexTransfer.java

package org.checkerframework.checker.index.searchindex;

import java.util.List;
import javax.lang.model.element.AnnotationMirror;
import org.checkerframework.checker.index.IndexAbstractTransfer;
import org.checkerframework.checker.index.qual.NegativeIndexFor;
import org.checkerframework.checker.index.qual.SearchIndexFor;
import org.checkerframework.common.value.ValueCheckerUtils;
import org.checkerframework.dataflow.analysis.TransferInput;
import org.checkerframework.dataflow.cfg.node.Node;
import org.checkerframework.dataflow.expression.JavaExpression;
import org.checkerframework.framework.flow.CFAnalysis;
import org.checkerframework.framework.flow.CFStore;
import org.checkerframework.framework.flow.CFValue;
import org.checkerframework.javacutil.AnnotationUtils;

/**
 * The transfer function for the SearchIndexFor checker. Allows {@link SearchIndexFor} to be refined
 * to {@link NegativeIndexFor}.
 *
 * <p>Contains 1 refinement rule: SearchIndexFor &rarr; NegativeIndexFor when compared against zero.
 */
public class SearchIndexTransfer extends IndexAbstractTransfer {

  // The ATF (Annotated Type Factory).
  private SearchIndexAnnotatedTypeFactory aTypeFactory;

  public SearchIndexTransfer(CFAnalysis analysis) {
    super(analysis);
    aTypeFactory = (SearchIndexAnnotatedTypeFactory) analysis.getTypeFactory();
  }

  /**
   * If a {@link SearchIndexFor} value is negative, then refine it to {@link NegativeIndexFor}. This
   * method is called by refinement rules for binary comparison operators.
   *
   * <p>If the left value (in a greater-than or greater-than-or-equal binary comparison) is exactly
   * the value of {@code valueToCompareTo}, and the right side has type {@link SearchIndexFor}, then
   * the right side's new value in the store should become {@link NegativeIndexFor}.
   *
   * <p>For example, this allows the following code to typecheck:
   *
   * <pre>
   * <code>
   * {@literal @}SearchIndexFor("a") int index = Arrays.binarySearch(a, y);
   *  if (index &lt; 0) {
   *    {@literal @}NegativeIndexFor("a") int negInsertionPoint = index;
   *  }
   * </code>
   * </pre>
   *
   * @param valueToCompareTo this value must be 0 (for greater than or less than) or -1 (for greater
   *     than or equal or less than or equal)
   */
  private void refineSearchIndexToNegativeIndexFor(
      Node left, Node right, CFStore store, int valueToCompareTo) {
    assert valueToCompareTo == 0 || valueToCompareTo == -1;
    Long leftValue =
        ValueCheckerUtils.getExactValue(
            left.getTree(), aTypeFactory.getValueAnnotatedTypeFactory());
    if (leftValue != null && leftValue == valueToCompareTo) {
      AnnotationMirror rightSIF =
          aTypeFactory.getAnnotationMirror(right.getTree(), SearchIndexFor.class);
      if (rightSIF != null) {
        List<String> arrays =
            AnnotationUtils.getElementValueArray(
                rightSIF, aTypeFactory.searchIndexForValueElement, String.class);
        AnnotationMirror nif = aTypeFactory.createNegativeIndexFor(arrays);
        store.insertValue(JavaExpression.fromNode(right), nif);
      }
    }
  }

  @Override
  protected void refineGT(
      Node left,
      AnnotationMirror leftAnno,
      Node right,
      AnnotationMirror rightAnno,
      CFStore store,
      TransferInput<CFValue, CFStore> in) {
    refineSearchIndexToNegativeIndexFor(left, right, store, 0);
  }

  @Override
  protected void refineGTE(
      Node left,
      AnnotationMirror leftAnno,
      Node right,
      AnnotationMirror rightAnno,
      CFStore store,
      TransferInput<CFValue, CFStore> in) {
    refineSearchIndexToNegativeIndexFor(left, right, store, -1);
  }
}