checker/src/main/java/org/checkerframework/checker/signedness/SignednessVisitor.java

package org.checkerframework.checker.signedness;

import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.CompoundAssignmentTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.Tree.Kind;
import org.checkerframework.checker.signedness.qual.PolySigned;
import org.checkerframework.checker.signedness.qual.Signed;
import org.checkerframework.checker.signedness.qual.Unsigned;
import org.checkerframework.common.basetype.BaseTypeChecker;
import org.checkerframework.common.basetype.BaseTypeVisitor;
import org.checkerframework.framework.type.AnnotatedTypeMirror;
import org.checkerframework.javacutil.Pair;

/**
 * The SignednessVisitor enforces the Signedness Checker rules. These rules are described in the
 * Checker Framework Manual.
 *
 * @checker_framework.manual #signedness-checker Signedness Checker
 */
public class SignednessVisitor extends BaseTypeVisitor<SignednessAnnotatedTypeFactory> {

  public SignednessVisitor(BaseTypeChecker checker) {
    super(checker);
  }

  /**
   * Determines if an annotated type is annotated as {@link Unsigned} or {@link PolySigned}
   *
   * @param type the annotated type to be checked
   * @return true if the annotated type is annotated as {@link Unsigned} or {@link PolySigned}
   */
  private boolean hasUnsignedAnnotation(AnnotatedTypeMirror type) {
    return type.hasAnnotation(Unsigned.class) || type.hasAnnotation(PolySigned.class);
  }

  /**
   * Determines if an annotated type is annotated as {@link Signed} or {@link PolySigned}
   *
   * @param type the annotated type to be checked
   * @return true if the annotated type is annotated as {@link Signed} or {@link PolySigned}
   */
  private boolean hasSignedAnnotation(AnnotatedTypeMirror type) {
    return type.hasAnnotation(Signed.class) || type.hasAnnotation(PolySigned.class);
  }

  /**
   * Enforces the following rules on binary operations involving Unsigned and Signed types:
   *
   * <ul>
   *   <li>Do not allow any Unsigned types or PolySigned types in {@literal {/, %}} operations.
   *   <li>Do not allow signed right shift {@literal {>>}} on an Unsigned type or a PolySigned type.
   *   <li>Do not allow unsigned right shift {@literal {>>>}} on a Signed type or a PolySigned type.
   *   <li>Allow any left shift {@literal {<<}}.
   *   <li>Do not allow non-equality comparisons {@literal {<, <=, >, >=}} on Unsigned types or
   *       PolySigned types.
   *   <li>Do not allow the mixing of Signed and Unsigned types.
   * </ul>
   */
  @Override
  public Void visitBinary(BinaryTree node, Void p) {
    // Used in diagnostic messages.
    ExpressionTree leftOp = node.getLeftOperand();
    ExpressionTree rightOp = node.getRightOperand();

    Pair<AnnotatedTypeMirror, AnnotatedTypeMirror> argTypes = atypeFactory.binaryTreeArgTypes(node);
    AnnotatedTypeMirror leftOpType = argTypes.first;
    AnnotatedTypeMirror rightOpType = argTypes.second;

    Kind kind = node.getKind();

    switch (kind) {
      case DIVIDE:
      case REMAINDER:
        if (hasUnsignedAnnotation(leftOpType)) {
          checker.reportError(leftOp, "operation.unsignedlhs", kind, leftOpType, rightOpType);
        } else if (hasUnsignedAnnotation(rightOpType)) {
          checker.reportError(rightOp, "operation.unsignedrhs", kind, leftOpType, rightOpType);
        }
        break;

      case RIGHT_SHIFT:
        if (hasUnsignedAnnotation(leftOpType)
            && !atypeFactory.isMaskedShiftEitherSignedness(node, getCurrentPath())
            && !atypeFactory.isCastedShiftEitherSignedness(node, getCurrentPath())) {
          checker.reportError(leftOp, "shift.signed", kind, leftOpType, rightOpType);
        }
        break;

      case UNSIGNED_RIGHT_SHIFT:
        if (hasSignedAnnotation(leftOpType)
            && !atypeFactory.isMaskedShiftEitherSignedness(node, getCurrentPath())
            && !atypeFactory.isCastedShiftEitherSignedness(node, getCurrentPath())) {
          checker.reportError(leftOp, "shift.unsigned", kind, leftOpType, rightOpType);
        }
        break;

      case LEFT_SHIFT:
        break;

      case GREATER_THAN:
      case GREATER_THAN_EQUAL:
      case LESS_THAN:
      case LESS_THAN_EQUAL:
        if (hasUnsignedAnnotation(leftOpType)) {
          checker.reportError(leftOp, "comparison.unsignedlhs", leftOpType, rightOpType);
        } else if (hasUnsignedAnnotation(rightOpType)) {
          checker.reportError(rightOp, "comparison.unsignedrhs", leftOpType, rightOpType);
        }
        break;

      case EQUAL_TO:
      case NOT_EQUAL_TO:
        if (leftOpType.hasAnnotation(Unsigned.class) && rightOpType.hasAnnotation(Signed.class)) {
          checker.reportError(node, "comparison.mixed.unsignedlhs", leftOpType, rightOpType);
        } else if (leftOpType.hasAnnotation(Signed.class)
            && rightOpType.hasAnnotation(Unsigned.class)) {
          checker.reportError(node, "comparison.mixed.unsignedrhs", leftOpType, rightOpType);
        }
        break;

      default:
        if (leftOpType.hasAnnotation(Unsigned.class) && rightOpType.hasAnnotation(Signed.class)) {
          checker.reportError(node, "operation.mixed.unsignedlhs", kind, leftOpType, rightOpType);
        } else if (leftOpType.hasAnnotation(Signed.class)
            && rightOpType.hasAnnotation(Unsigned.class)) {
          checker.reportError(node, "operation.mixed.unsignedrhs", kind, leftOpType, rightOpType);
        }
        break;
    }
    return super.visitBinary(node, p);
  }

  /** @return a string representation of kind, with trailing _ASSIGNMENT stripped off if any */
  private String kindWithoutAssignment(Kind kind) {
    String result = kind.toString();
    if (result.endsWith("_ASSIGNMENT")) {
      return result.substring(0, result.length() - "_ASSIGNMENT".length());
    } else {
      return result;
    }
  }

  /**
   * Enforces the following rules on compound assignments involving Unsigned and Signed types:
   *
   * <ul>
   *   <li>Do not allow any Unsigned types or PolySigned types in {@literal {/=, %=}} assignments.
   *   <li>Do not allow signed right shift {@literal {>>=}} to assign to an Unsigned type or a
   *       PolySigned type.
   *   <li>Do not allow unsigned right shift {@literal {>>>=}} to assign to a Signed type or a
   *       PolySigned type.
   *   <li>Allow any left shift {@literal {<<=}} assignment.
   *   <li>Do not allow mixing of Signed and Unsigned types.
   * </ul>
   */
  @Override
  public Void visitCompoundAssignment(CompoundAssignmentTree node, Void p) {

    ExpressionTree var = node.getVariable();
    ExpressionTree expr = node.getExpression();

    Pair<AnnotatedTypeMirror, AnnotatedTypeMirror> argTypes =
        atypeFactory.compoundAssignmentTreeArgTypes(node);
    AnnotatedTypeMirror varType = argTypes.first;
    AnnotatedTypeMirror exprType = argTypes.second;

    Kind kind = node.getKind();

    switch (kind) {
      case DIVIDE_ASSIGNMENT:
      case REMAINDER_ASSIGNMENT:
        if (hasUnsignedAnnotation(varType)) {
          checker.reportError(
              var,
              "compound.assignment.unsigned.variable",
              kindWithoutAssignment(kind),
              varType,
              exprType);
        } else if (hasUnsignedAnnotation(exprType)) {
          checker.reportError(
              expr,
              "compound.assignment.unsigned.expression",
              kindWithoutAssignment(kind),
              varType,
              exprType);
        }
        break;

      case RIGHT_SHIFT_ASSIGNMENT:
        if (hasUnsignedAnnotation(varType)) {
          checker.reportError(
              var,
              "compound.assignment.shift.signed",
              kindWithoutAssignment(kind),
              varType,
              exprType);
        }
        break;

      case UNSIGNED_RIGHT_SHIFT_ASSIGNMENT:
        if (hasSignedAnnotation(varType)) {
          checker.reportError(
              var,
              "compound.assignment.shift.unsigned",
              kindWithoutAssignment(kind),
              varType,
              exprType);
        }
        break;

      case LEFT_SHIFT_ASSIGNMENT:
        break;

      default:
        if (varType.hasAnnotation(Unsigned.class) && exprType.hasAnnotation(Signed.class)) {
          checker.reportError(
              expr,
              "compound.assignment.mixed.unsigned.variable",
              kindWithoutAssignment(kind),
              varType,
              exprType);
        } else if (varType.hasAnnotation(Signed.class) && exprType.hasAnnotation(Unsigned.class)) {
          checker.reportError(
              expr,
              "compound.assignment.mixed.unsigned.expression",
              kindWithoutAssignment(kind),
              varType,
              exprType);
        }
        break;
    }
    return super.visitCompoundAssignment(node, p);
  }
}