elaborate() {
    return stripIndent`
      This "if" block requires corresponding "else" block which will be
      evaluated when ${generate(this.node.test)} expression evaluates to false.

      Later in the course we will lift this restriction and allow "if" without
      else.
    `
  }

  elaborate() {
    let ifOrElse
    let header
    let body
    if (this.type === 'consequent') {
      ifOrElse = 'if'
      header = `if (${generate(this.node.test)})`
      body = this.node.consequent
    } else {
      ifOrElse = header = 'else'
      body = this.node.alternate
    }

    return stripIndent`
      ${ifOrElse} block need to be enclosed with a pair of curly braces.

      ${header} {
        ${generate(body)}
      }

      An exception is when you have an "if" followed by "else if", in this case
      "else if" block does not need to be surrounded by curly braces.

      if (someCondition) {
        // ...
      } else /* notice missing { here */ if (someCondition) {
        // ...
      } else {
        // ...
      }

      Rationale: Readability in dense packed code.

      In the snippet below, for instance, with poor indentation it is easy to
      mistaken hello() and world() to belong to the same branch of logic.

      if (someCondition) {
        2;
      } else
        hello();
      world();

    `
  }

  function astToHDWalletProvider(node: ESTree.NewExpression): IProvider {
    const provider: IProvider = {
      raw: generate(node),
    };

    const mnemonicNode = node.arguments[0];
    if (mnemonicNode && mnemonicNode.type === 'Literal') {
      provider.mnemonic = '' + mnemonicNode.value;
    }

    const urlNode = node.arguments[1];
    if (urlNode && urlNode.type === 'Literal') {
      provider.url = '' + urlNode.value;
    }

    if (urlNode && urlNode.type !== 'Literal') {
      provider.url = generate(urlNode);
    }

    return provider;
  }

  tests.forEach(t => {
    const generator = evaluators[t.statement.type](t.statement, state)
    let isDone = false

    while (!isDone) {
      const g = generator.next()
      isDone = g.done
      state = g.value
    }

    if (state.value !== t.expectedValue) {
      // tslint:disable-next-line
      console.log(`L${t.statement.loc!.start.line}: ${generate(t.statement)}`)
    }

    expect(state.value).toBe(t.expectedValue)
  })

export const testVisualizer = (program: string, expectedOutput: string[]) => {
  let state = createInterpreter()
  let visualizer = create()

  const node = parse(program, 3).parser.program!
  const evaluator = evalProgram(node, state)
  const prints = []

  let gen = evaluator.next()
  while (gen) {
    state = gen.value
    if (!state) {
      break
    }
    const prev = visualizer
    visualizer = next(visualizer, state)
    if (visualizer.root && visualizer.id !== prev.id) {
      prints.push(generate(visualizer.root))
    }
    gen = evaluator.next()
  }
  expect(prints).toEqual(expectedOutput)
}

 const fixs = this.fixs.map(n => '\t' + generate(n)).join('\n')

 public async writeAST(): Promise<void> {
   return fs.writeFile(this.filePath, generate(this.ast as ESTree.Node, {comments: true}));
 }

import { baseGenerator, generate } from "astring";
import { FunctionExpression, MemberExpression, Program } from "estree";
import { Stream } from "stream";

const ast: Program = null;
const functionE: FunctionExpression = null;
const memberE: MemberExpression = null;

// should accept different nodes
generate(ast);
generate(functionE);
generate(memberE);

// options without output option should generate string
const string: string = generate(ast, {
    comments: true,
    generator: baseGenerator,
    indent: "\t",
    lineEnd: "\n",
    startingIndentLevel: 42,
    sourceMap: null
});

// options with output option should return Stream
const stream: Stream = generate(ast, {
    output: new Stream()
});

// Generator should map node types to functions whose first parameter is same node type
baseGenerator.Program(ast, { write(s: string) { return; } });
baseGenerator.FunctionExpression(functionE, { write(s: string) { return; } });