checker/src/main/java/org/checkerframework/checker/units/UnitsVisitor.java

package org.checkerframework.checker.units;

import com.sun.source.tree.CompoundAssignmentTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.Tree.Kind;
import org.checkerframework.checker.units.qual.UnknownUnits;
import org.checkerframework.common.basetype.BaseTypeChecker;
import org.checkerframework.common.basetype.BaseTypeVisitor;
import org.checkerframework.framework.type.AnnotatedTypeMirror;

/**
 * Units visitor.
 *
 * <p>Ensure consistent use of compound assignments.
 */
public class UnitsVisitor extends BaseTypeVisitor<UnitsAnnotatedTypeFactory> {
  public UnitsVisitor(BaseTypeChecker checker) {
    super(checker);
  }

  @Override
  public Void visitCompoundAssignment(CompoundAssignmentTree node, Void p) {
    ExpressionTree var = node.getVariable();
    ExpressionTree expr = node.getExpression();
    AnnotatedTypeMirror varType = atypeFactory.getAnnotatedType(var);
    AnnotatedTypeMirror exprType = atypeFactory.getAnnotatedType(expr);

    Kind kind = node.getKind();

    if ((kind == Kind.PLUS_ASSIGNMENT || kind == Kind.MINUS_ASSIGNMENT)) {
      if (!atypeFactory.getTypeHierarchy().isSubtype(exprType, varType)) {
        checker.reportError(node, "compound.assignment", varType, exprType);
      }
    } else if (exprType.getAnnotation(UnknownUnits.class) == null) {
      // Only allow mul/div with unqualified units
      checker.reportError(node, "compound.assignment", varType, exprType);
    }

    return null; // super.visitCompoundAssignment(node, p);
  }
}