text: // Copyright 2013 Traceur Authors.
  //
  // Licensed 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.
  
  import {
    FunctionBody,
    Script
  } from '../syntax/trees/ParseTrees.js';
  import {ParseTreeTransformer} from './ParseTreeTransformer.js';
  import {createUseStrictDirective} from './ParseTreeFactory.js';
  import {hasUseStrict} from '../semantics/util.js';
  
  function prepend(statements) {
    return [
      createUseStrictDirective(),
      ...statements
    ]
  }
  
  /**
   * This makes the code strict. It will add 'use strict' to Script and
   * FunctionBody as needed.
   */
  export class MakeStrictTransformer extends ParseTreeTransformer {
    transformScript(tree) {
      if (hasUseStrict(tree.scriptItemList))
        return tree;
  
      return new Script(tree.location, prepend(tree.scriptItemList),
                        tree.moduleName);
    }
    transformFunctionBody(tree) {
      if (hasUseStrict(tree.statements))
        return tree;
      return new FunctionBody(tree.location, prepend(tree.statements));
    }
  
    static transformTree(tree) {
      return new MakeStrictTransformer().transformAny(tree);
    }
  }
  