content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you 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 org.apache.calcite.linq4j.tree;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.Objects;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Represents an unconditional jump. This includes return statements, break and
   * continue statements, and other jumps.
   */
  public class GotoStatement extends Statement {
    public final GotoExpressionKind kind;
    public final @Nullable LabelTarget labelTarget;
    public final @Nullable Expression expression;
  
    GotoStatement(GotoExpressionKind kind, @Nullable LabelTarget labelTarget,
        @Nullable Expression expression) {
      super(ExpressionType.Goto,
          expression == null ? Void.TYPE : expression.getType());
      this.kind = requireNonNull(kind, "kind");
      this.labelTarget = labelTarget;
      this.expression = expression;
  
      switch (kind) {
      case Break:
      case Continue:
        checkArgument(expression == null, "for %s, expression must be null",
            kind);
        break;
      case Goto:
        assert expression == null;
        requireNonNull(labelTarget, "labelTarget");
        break;
      case Return:
      case Sequence:
        checkArgument(labelTarget == null, "for %s, labelTarget must be null",
            kind);
        break;
      default:
        throw new RuntimeException("unexpected: " + kind);
      }
    }
  
    @Override public Statement accept(Shuttle shuttle) {
      shuttle = shuttle.preVisit(this);
      Expression expression1 =
          expression == null ? null : expression.accept(shuttle);
      return shuttle.visit(this, expression1);
    }
  
    @Override public <R> R accept(Visitor<R> visitor) {
      return visitor.visit(this);
    }
  
    @Override void accept0(ExpressionWriter writer) {
      writer.append(kind.prefix);
      if (labelTarget != null) {
        writer.append(' ').append(labelTarget.name);
      }
      if (expression != null) {
        if (!kind.prefix.isEmpty()) {
          writer.append(' ');
        }
        switch (kind) {
        case Sequence:
          // don't indent for sequence
          expression.accept(writer, 0, 0);
          break;
        default:
          writer.begin();
          expression.accept(writer, 0, 0);
          writer.end();
        }
      }
      writer.append(';').newlineAndIndent();
    }
  
    @Override public @Nullable Object evaluate(Evaluator evaluator) {
      switch (kind) {
      case Return:
      case Sequence:
        // NOTE: We ignore control flow. This is only correct if "return"
        // is the last statement in the block.
        return requireNonNull(expression, "expression").evaluate(evaluator);
      default:
        throw new AssertionError("evaluate not implemented");
      }
    }
  
    @Override public boolean equals(@Nullable Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }
      if (!super.equals(o)) {
        return false;
      }
  
      GotoStatement that = (GotoStatement) o;
      return Objects.equals(expression, that.expression)
          && kind == that.kind
          && Objects.equals(labelTarget, that.labelTarget);
    }
  
    @Override public int hashCode() {
      return Objects.hash(nodeType, type, kind, labelTarget, expression);
    }
  }
  