statementsToStateMachine_(statements) {
    let startState = this.allocateState();
    let fallThroughState = this.allocateState();
    return this.stateToStateMachine_(
        new FallThroughState(
            startState,
            fallThroughState,
            statements),
        fallThroughState);
  }
Converts a list of statements into a state machine. The statements may not
contain a yield statement directly or indirectly.
@param {Array.<ParseTree>} statements
@return {StateMachine}