ben-sb-shift-codegen/src/minimal-codegen.js

code generator for Shift format ASTs (forked for use in https://github.com/ben-sb/javascript-deobfuscator)

const objectAssign = require('object-assign');
const { keyword } = require('esutils');
const { Precedence, getPrecedence, escapeStringLiteral, Empty, Token, RawToken, NumberCodeRep, Paren, Bracket, Brace, NoIn, ContainsIn, Seq, Semi, CommaSep, SemiOp } = require('./coderep');

function p(node, precedence, a) {
  return getPrecedence(node) < precedence ? paren(a) : a;
}

function t(token, isRegExp = false) {
  return new Token(token, isRegExp);
}

function paren(rep) {
  return new Paren(rep);
}

function brace(rep) {
  return new Brace(rep);
}

function bracket(rep) {
  return new Bracket(rep);
}

function noIn(rep) {
  return new NoIn(rep);
}

function markContainsIn(state) {
  return state.containsIn ? new ContainsIn(state) : state;
}

function seq(...reps) {
  return new Seq(reps);
}

function semi() {
  return new Semi;
}

function semiOp() {
  return new SemiOp;
}

function empty() {
  return new Empty;
}

function commaSep(pieces) {
  return new CommaSep(pieces);
}

function getAssignmentExpr(state) {
  return state ? state.containsGroup ? paren(state) : state : empty();
}

class MinimalCodeGen {
  parenToAvoidBeingDirective(element, original) {
    if (element && element.type === 'ExpressionStatement' && element.expression.type === 'LiteralStringExpression') {
      return seq(paren(original.children[0]), semiOp());
    }
    return original;
  }

  regenerateArrowParams(element, original) {
    if (element.rest == null && element.items.length === 1 && element.items[0].type === 'BindingIdentifier') {
      // FormalParameters unconditionally include parentheses, but they're not necessary here
      return this.reduceBindingIdentifier(element.items[0]);
    }
    return original;
  }

  reduceArrayExpression(node, { elements }) {
    if (elements.length === 0) {
      return bracket(empty());
    }

    let content = commaSep(elements.map(getAssignmentExpr));
    if (elements.length > 0 && elements[elements.length - 1] == null) {
      content = seq(content, t(','));
    }
    return bracket(content);
  }

  reduceAwaitExpression(node, { expression }) {
    return seq(t('await'), p(node.expression, getPrecedence(node), expression));
  }

  reduceSpreadElement(node, { expression }) {
    return seq(t('...'), p(node.expression, Precedence.Assignment, expression));
  }

  reduceSpreadProperty(node, { expression }) {
    return seq(t('...'), getAssignmentExpr(expression));
  }

  reduceAssignmentExpression(node, { binding, expression }) {
    let leftCode = binding;
    let rightCode = expression;
    let containsIn = expression.containsIn;
    let startsWithCurly = binding.startsWithCurly;
    let startsWithLetSquareBracket = binding.startsWithLetSquareBracket;
    let startsWithFunctionOrClass = binding.startsWithFunctionOrClass;
    if (getPrecedence(node.expression) < getPrecedence(node)) {
      rightCode = paren(rightCode);
      containsIn = false;
    }
    return objectAssign(seq(leftCode, t('='), rightCode), { containsIn, startsWithCurly, startsWithLetSquareBracket, startsWithFunctionOrClass });
  }

  reduceAssignmentTargetIdentifier(node) {
    let a = t(node.name);
    if (node.name === 'let') {
      a.startsWithLet = true;
    }
    return a;
  }

  reduceAssignmentTargetWithDefault(node, { binding, init }) {
    return seq(binding, t('='), p(node.init, Precedence.Assignment, init));
  }

  reduceCompoundAssignmentExpression(node, { binding, expression }) {
    let leftCode = binding;
    let rightCode = expression;
    let containsIn = expression.containsIn;
    let startsWithCurly = binding.startsWithCurly;
    let startsWithLetSquareBracket = binding.startsWithLetSquareBracket;
    let startsWithFunctionOrClass = binding.startsWithFunctionOrClass;
    if (getPrecedence(node.expression) < getPrecedence(node)) {
      rightCode = paren(rightCode);
      containsIn = false;
    }
    return objectAssign(seq(leftCode, t(node.operator), rightCode), { containsIn, startsWithCurly, startsWithLetSquareBracket, startsWithFunctionOrClass });
  }

  reduceBinaryExpression(node, { left, right }) {
    let leftCode = left;
    let startsWithCurly = left.startsWithCurly;
    let startsWithLetSquareBracket = left.startsWithLetSquareBracket;
    let startsWithFunctionOrClass = left.startsWithFunctionOrClass;
    let leftContainsIn = left.containsIn;
    let isRightAssociative = node.operator === '**';
    if (getPrecedence(node.left) < getPrecedence(node) || isRightAssociative && (getPrecedence(node.left) === getPrecedence(node) || node.left.type === 'UnaryExpression')) {
      leftCode = paren(leftCode);
      startsWithCurly = false;
      startsWithLetSquareBracket = false;
      startsWithFunctionOrClass = false;
      leftContainsIn = false;
    }
    let rightCode = right;
    let rightContainsIn = right.containsIn;
    if (getPrecedence(node.right) < getPrecedence(node) || !isRightAssociative && getPrecedence(node.right) === getPrecedence(node)) {
      rightCode = paren(rightCode);
      rightContainsIn = false;
    }
    return objectAssign(
      seq(leftCode, t(node.operator), rightCode),
      {
        containsIn: leftContainsIn || rightContainsIn || node.operator === 'in',
        containsGroup: node.operator === ',',
        startsWithCurly,
        startsWithLetSquareBracket,
        startsWithFunctionOrClass,
      }
    );
  }

  reduceBindingWithDefault(node, { binding, init }) {
    return seq(binding, t('='), p(node.init, Precedence.Assignment, init));
  }

  reduceBindingIdentifier(node) {
    let a = t(node.name);
    if (node.name === 'let') {
      a.startsWithLet = true;
    }
    return a;
  }

  reduceArrayAssignmentTarget(node, { elements, rest }) {
    let content;
    if (elements.length === 0) {
      content = rest == null ? empty() : seq(t('...'), rest);
    } else {
      elements = elements.concat(rest == null ? [] : [seq(t('...'), rest)]);
      content = commaSep(elements.map(getAssignmentExpr));
      if (elements.length > 0 && elements[elements.length - 1] == null) {
        content = seq(content, t(','));
      }
    }
    return bracket(content);
  }

  reduceArrayBinding(node, { elements, rest }) {
    let content;
    if (elements.length === 0) {
      content = rest == null ? empty() : seq(t('...'), rest);
    } else {
      elements = elements.concat(rest == null ? [] : [seq(t('...'), rest)]);
      content = commaSep(elements.map(getAssignmentExpr));
      if (elements.length > 0 && elements[elements.length - 1] == null) {
        content = seq(content, t(','));
      }
    }
    return bracket(content);
  }

  reduceObjectAssignmentTarget(node, { properties, rest }) {
    let content = commaSep(properties);
    if (properties.length === 0) {
      content = rest == null ? empty() : seq(t('...'), rest);
    } else {
      content = rest == null ? content : seq(content, t(','), t('...'), rest);
    }
    let state = brace(content);
    state.startsWithCurly = true;
    return state;
  }

  reduceObjectBinding(node, { properties, rest }) {
    let content = commaSep(properties);
    if (properties.length === 0) {
      content = rest == null ? empty() : seq(t('...'), rest);
    } else {
      content = rest == null ? content : seq(content, t(','), t('...'), rest);
    }
    let state = brace(content);
    state.startsWithCurly = true;
    return state;
  }

  reduceAssignmentTargetPropertyIdentifier(node, { binding, init }) {
    if (node.init == null) return binding;
    return seq(binding, t('='), p(node.init, Precedence.Assignment, init));
  }

  reduceAssignmentTargetPropertyProperty(node, { name, binding }) {
    return seq(name, t(':'), binding);
  }

  reduceBindingPropertyIdentifier(node, { binding, init }) {
    if (node.init == null) return binding;
    return seq(binding, t('='), p(node.init, Precedence.Assignment, init));
  }

  reduceBindingPropertyProperty(node, { name, binding }) {
    return seq(name, t(':'), binding);
  }

  reduceBlock(node, { statements }) {
    return brace(seq(...statements));
  }

  reduceBlockStatement(node, { block }) {
    return block;
  }

  reduceBreakStatement(node) {
    return seq(t('break'), node.label ? t(node.label) : empty(), semiOp());
  }

  reduceCallExpression(node, { callee, arguments: args }) {
    const parenthizedArgs = args.map((a, i) => p(node.arguments[i], Precedence.Assignment, a));
    return objectAssign(
      seq(p(node.callee, getPrecedence(node), callee), paren(commaSep(parenthizedArgs))),
      {
        startsWithCurly: callee.startsWithCurly,
        startsWithLet: callee.startsWithLet,
        startsWithLetSquareBracket: callee.startsWithLetSquareBracket,
        startsWithFunctionOrClass: callee.startsWithFunctionOrClass,
      }
    );
  }

  reduceCatchClause(node, { binding, body }) {
    if (binding == null) {
      return seq(t('catch'), body);
    }
    return seq(t('catch'), paren(binding), body);
  }

  reduceClassDeclaration(node, { name, super: _super, elements }) {
    let state = seq(t('class'), node.name.name === '*default*' ? empty() : name);
    if (_super != null) {
      state = seq(state, t('extends'), p(node.super, Precedence.New, _super));
    }
    state = seq(state, t('{'), ...elements, t('}'));
    return state;
  }

  reduceClassExpression(node, { name, super: _super, elements }) {
    let state = t('class');
    if (name != null) {
      state = seq(state, name);
    }
    if (_super != null) {
      state = seq(state, t('extends'), p(node.super, Precedence.New, _super));
    }
    state = seq(state, t('{'), ...elements, t('}'));
    state.startsWithFunctionOrClass = true;
    return state;
  }

  reduceClassElement(node, { method }) {
    if (!node.isStatic) return method;
    return seq(t('static'), method);
  }

  reduceComputedMemberAssignmentTarget(node, { object, expression }) {
    let startsWithLetSquareBracket =
      object.startsWithLetSquareBracket ||
      node.object.type === 'IdentifierExpression' && node.object.name === 'let';
    return objectAssign(
      seq(p(node.object, getPrecedence(node), object), bracket(expression)),
      {
        startsWithLet: object.startsWithLet,
        startsWithLetSquareBracket,
        startsWithCurly: object.startsWithCurly,
        startsWithFunctionOrClass: object.startsWithFunctionOrClass,
      }
    );
  }

  reduceComputedMemberExpression(node, { object, expression }) {
    let startsWithLetSquareBracket =
      object.startsWithLetSquareBracket ||
      node.object.type === 'IdentifierExpression' && node.object.name === 'let';
    return objectAssign(
      seq(p(node.object, getPrecedence(node), object), bracket(expression)),
      {
        startsWithLet: object.startsWithLet,
        startsWithLetSquareBracket,
        startsWithCurly: object.startsWithCurly,
        startsWithFunctionOrClass: object.startsWithFunctionOrClass,
      }
    );
  }

  reduceComputedPropertyName(node, { expression }) {
    return bracket(p(node.expression, Precedence.Assignment, expression));
  }

  reduceConditionalExpression(node, { test, consequent, alternate }) {
    let containsIn = test.containsIn || alternate.containsIn;
    let startsWithCurly = test.startsWithCurly;
    let startsWithLetSquareBracket = test.startsWithLetSquareBracket;
    let startsWithFunctionOrClass = test.startsWithFunctionOrClass;
    return objectAssign(
      seq(
        p(node.test, Precedence.LogicalOR, test), t('?'),
        p(node.consequent, Precedence.Assignment, consequent), t(':'),
        p(node.alternate, Precedence.Assignment, alternate)), {
        containsIn,
        startsWithCurly,
        startsWithLetSquareBracket,
        startsWithFunctionOrClass,
      });
  }

  reduceContinueStatement(node) {
    return seq(t('continue'), node.label ? t(node.label) : empty(), semiOp());
  }

  reduceDataProperty(node, { name, expression }) {
    return seq(name, t(':'), getAssignmentExpr(expression));
  }

  reduceDebuggerStatement(/* node */) {
    return seq(t('debugger'), semiOp());
  }

  reduceDoWhileStatement(node, { body, test }) {
    return seq(t('do'), body, t('while'), paren(test), semiOp());
  }

  reduceEmptyStatement(/* node */) {
    return semi();
  }

  reduceExpressionStatement(node, { expression }) {
    let needsParens =
      expression.startsWithCurly ||
      expression.startsWithLetSquareBracket ||
      expression.startsWithFunctionOrClass;
    return seq(needsParens ? paren(expression) : expression, semiOp());
  }

  reduceForInStatement(node, { left, right, body }) {
    left = node.left.type === 'VariableDeclaration' ? noIn(markContainsIn(left)) : left;
    return objectAssign(
      seq(t('for'), paren(seq(left.startsWithLet ? paren(left) : left, t('in'), right)), body),
      { endsWithMissingElse: body.endsWithMissingElse });
  }

  reduceForOfStatement(node, { left, right, body }) {
    left = node.left.type === 'VariableDeclaration' ? noIn(markContainsIn(left)) : left;
    return objectAssign(
      seq(t('for'), paren(seq(left.startsWithLet ? paren(left) : left, t('of'), p(node.right, Precedence.Assignment, right))), body),
      { endsWithMissingElse: body.endsWithMissingElse });
  }

  reduceForStatement(node, { init, test, update, body }) {
    if (init) {
      if (init.startsWithLetSquareBracket) {
        init = paren(init);
      }
      init = noIn(markContainsIn(init));
    }
    return objectAssign(
      seq(
        t('for'),
        paren(seq(init ? init : empty(), semi(), test || empty(), semi(), update || empty())),
        body),
      {
        endsWithMissingElse: body.endsWithMissingElse,
      });
  }

  reduceForAwaitStatement(node, { left, right, body }) {
    left = node.left.type === 'VariableDeclaration' ? noIn(markContainsIn(left)) : left;
    return objectAssign(
      seq(t('for'), t('await'), paren(seq(left.startsWithLet ? paren(left) : left, t('of'), p(node.right, Precedence.Assignment, right))), body),
      { endsWithMissingElse: body.endsWithMissingElse });
  }

  reduceFunctionBody(node, { directives, statements }) {
    if (statements.length) {
      statements[0] = this.parenToAvoidBeingDirective(node.statements[0], statements[0]);
    }
    return brace(seq(...directives, ...statements));
  }

  reduceFunctionDeclaration(node, { name, params, body }) {
    return seq(node.isAsync ? t('async') : empty(), t('function'), node.isGenerator ? t('*') : empty(), node.name.name === '*default*' ? empty() : name, params, body);
  }

  reduceFunctionExpression(node, { name, params, body }) {
    let state = seq(node.isAsync ? t('async') : empty(), t('function'), node.isGenerator ? t('*') : empty(), name ? name : empty(), params, body);
    state.startsWithFunctionOrClass = true;
    return state;
  }

  reduceFormalParameters(node, { items, rest }) {
    return paren(commaSep(items.concat(rest == null ? [] : [seq(t('...'), rest)])));
  }

  reduceArrowExpression(node, { params, body }) {
    params = this.regenerateArrowParams(node.params, params);
    let containsIn = false;
    if (node.body.type !== 'FunctionBody') {
      if (body.startsWithCurly) {
        body = paren(body);
      } else if (body.containsIn) {
        containsIn = true;
      }
    }
    return objectAssign(seq(node.isAsync ? t('async') : empty(), params, t('=>'), p(node.body, Precedence.Assignment, body)), { containsIn });
  }

  reduceGetter(node, { name, body }) {
    return seq(t('get'), name, paren(empty()), body);
  }

  reduceIdentifierExpression(node) {
    let a = t(node.name);
    if (node.name === 'let') {
      a.startsWithLet = true;
    }
    return a;
  }

  reduceIfStatement(node, { test, consequent, alternate }) {
    if (alternate && consequent.endsWithMissingElse) {
      consequent = brace(consequent);
    }
    return objectAssign(
      seq(t('if'), paren(test), consequent, alternate ? seq(t('else'), alternate) : empty()),
      { endsWithMissingElse: alternate ? alternate.endsWithMissingElse : true });
  }

  reduceImport(node, { defaultBinding, namedImports }) {
    let bindings = [];
    if (defaultBinding != null) {
      bindings.push(defaultBinding);
    }
    if (namedImports.length > 0) {
      bindings.push(brace(commaSep(namedImports)));
    }
    if (bindings.length === 0) {
      return seq(t('import'), t(escapeStringLiteral(node.moduleSpecifier)), semiOp());
    }
    return seq(t('import'), commaSep(bindings), t('from'), t(escapeStringLiteral(node.moduleSpecifier)), semiOp());
  }

  reduceImportNamespace(node, { defaultBinding, namespaceBinding }) {
    return seq(
      t('import'),
      defaultBinding == null ? empty() : seq(defaultBinding, t(',')),
      t('*'),
      t('as'),
      namespaceBinding,
      t('from'),
      t(escapeStringLiteral(node.moduleSpecifier)),
      semiOp()
    );
  }

  reduceImportSpecifier(node, { binding }) {
    if (node.name == null) return binding;
    return seq(t(node.name), t('as'), binding);
  }

  reduceExportAllFrom(node) {
    return seq(t('export'), t('*'), t('from'), t(escapeStringLiteral(node.moduleSpecifier)), semiOp());
  }

  reduceExportFrom(node, { namedExports }) {
    return seq(t('export'), brace(commaSep(namedExports)), t('from'), t(escapeStringLiteral(node.moduleSpecifier)), semiOp());
  }

  reduceExportLocals(node, { namedExports }) {
    return seq(t('export'), brace(commaSep(namedExports)), semiOp());
  }

  reduceExport(node, { declaration }) {
    switch (node.declaration.type) {
      case 'FunctionDeclaration':
      case 'ClassDeclaration':
        break;
      default:
        declaration = seq(declaration, semiOp());
    }
    return seq(t('export'), declaration);
  }

  reduceExportDefault(node, { body }) {
    body = body.startsWithFunctionOrClass ? paren(body) : body;
    switch (node.body.type) {
      case 'FunctionDeclaration':
      case 'ClassDeclaration':
        return seq(t('export default'), body);
      default:
        return seq(t('export default'), p(node.body, Precedence.Assignment, body), semiOp());
    }
  }

  reduceExportFromSpecifier(node) {
    if (node.exportedName == null) return t(node.name);
    return seq(t(node.name), t('as'), t(node.exportedName));
  }

  reduceExportLocalSpecifier(node, { name }) {
    if (node.exportedName == null) return name;
    return seq(name, t('as'), t(node.exportedName));
  }

  reduceLabeledStatement(node, { body }) {
    return objectAssign(seq(t(node.label + ':'), body), { endsWithMissingElse: body.endsWithMissingElse });
  }

  reduceLiteralBooleanExpression(node) {
    return t(node.value.toString());
  }

  reduceLiteralNullExpression(/* node */) {
    return t('null');
  }

  reduceLiteralInfinityExpression(/* node */) {
    return t('2e308');
  }

  reduceLiteralNumericExpression(node) {
    return new NumberCodeRep(node.value);
  }

  reduceLiteralRegExpExpression(node) {
    return t(`/${node.pattern}/${node.global ? 'g' : ''}${node.ignoreCase ? 'i' : ''}${node.multiLine ? 'm' : ''}${node.dotAll ? 's' : ''}${node.unicode ? 'u' : ''}${node.sticky ? 'y' : ''}`, true);
  }

  reduceLiteralStringExpression(node) {
    return t(escapeStringLiteral(node.value));
  }

  reduceMethod(node, { name, params, body }) {
    return seq(node.isAsync ? t('async') : empty(), node.isGenerator ? t('*') : empty(), name, params, body);
  }

  reduceModule(node, { directives, items }) {
    if (items.length) {
      items[0] = this.parenToAvoidBeingDirective(node.items[0], items[0]);
    }
    return seq(...directives, ...items);
  }

  reduceNewExpression(node, { callee, arguments: args }) {
    const parenthizedArgs = args.map((a, i) => p(node.arguments[i], Precedence.Assignment, a));
    let calleeRep = getPrecedence(node.callee) === Precedence.Call ? paren(callee) :
      p(node.callee, getPrecedence(node), callee);
    return seq(t('new'), calleeRep, args.length === 0 ? empty() : paren(commaSep(parenthizedArgs)));
  }

  reduceNewTargetExpression() {
    return t('new.target');
  }

  reduceObjectExpression(node, { properties }) {
    let state = brace(commaSep(properties));
    state.startsWithCurly = true;
    return state;
  }

  reduceUpdateExpression(node, { operand }) {
    if (node.isPrefix) {
      return this.reduceUnaryExpression(...arguments);
    }
    return objectAssign(
      seq(p(node.operand, Precedence.New, operand), t(node.operator)),
      {
        startsWithCurly: operand.startsWithCurly,
        startsWithLetSquareBracket: operand.startsWithLetSquareBracket,
        startsWithFunctionOrClass: operand.startsWithFunctionOrClass,
      }
    );

  }

  reduceUnaryExpression(node, { operand }) {
    return seq(t(node.operator), p(node.operand, getPrecedence(node), operand));
  }

  reduceReturnStatement(node, { expression }) {
    return seq(t('return'), expression || empty(), semiOp());
  }

  reduceScript(node, { directives, statements }) {
    if (statements.length) {
      statements[0] = this.parenToAvoidBeingDirective(node.statements[0], statements[0]);
    }
    return seq(...directives, ...statements);
  }

  reduceSetter(node, { name, param, body }) {
    return seq(t('set'), name, paren(param), body);
  }

  reduceShorthandProperty(node, { name }) {
    return name;
  }

  reduceStaticMemberAssignmentTarget(node, { object }) {
    const state = seq(p(node.object, getPrecedence(node), object), t('.'), t(node.property));
    state.startsWithLet = object.startsWithLet;
    state.startsWithCurly = object.startsWithCurly;
    state.startsWithLetSquareBracket = object.startsWithLetSquareBracket;
    state.startsWithFunctionOrClass = object.startsWithFunctionOrClass;
    return state;
  }

  reduceStaticMemberExpression(node, { object }) {
    const state = seq(p(node.object, getPrecedence(node), object), t('.'), t(node.property));
    state.startsWithLet = object.startsWithLet;
    state.startsWithCurly = object.startsWithCurly;
    state.startsWithLetSquareBracket = object.startsWithLetSquareBracket;
    state.startsWithFunctionOrClass = object.startsWithFunctionOrClass;
    return state;
  }

  reduceStaticPropertyName(node) {
    if (keyword.isIdentifierNameES6(node.value)) {
      return t(node.value);
    }
    let n = parseFloat(node.value);
    if (n >= 0 && n.toString() === node.value) {
      return new NumberCodeRep(n);
    }
    return t(escapeStringLiteral(node.value));
  }

  reduceSuper() {
    return t('super');
  }

  reduceSwitchCase(node, { test, consequent }) {
    return seq(t('case'), test, t(':'), seq(...consequent));
  }

  reduceSwitchDefault(node, { consequent }) {
    return seq(t('default:'), seq(...consequent));
  }

  reduceSwitchStatement(node, { discriminant, cases }) {
    return seq(t('switch'), paren(discriminant), brace(seq(...cases)));
  }

  reduceSwitchStatementWithDefault(node, { discriminant, preDefaultCases, defaultCase, postDefaultCases }) {
    return seq(
      t('switch'),
      paren(discriminant),
      brace(seq(...preDefaultCases, defaultCase, ...postDefaultCases)));
  }

  reduceTemplateExpression(node, { tag, elements }) {
    let state = node.tag == null ? empty() : p(node.tag, getPrecedence(node), tag);
    state = seq(state, t('`'));
    for (let i = 0, l = node.elements.length; i < l; ++i) {
      if (node.elements[i].type === 'TemplateElement') {
        state = seq(
          state,
          i > 0 ? t('}') : empty(),
          elements[i],
          i < l - 1 ? t('${') : empty()
        );
      } else {
        state = seq(state, elements[i]);
      }
    }
    state = seq(state, t('`'));
    if (node.tag != null) {
      state.startsWithCurly = tag.startsWithCurly;
      state.startsWithLet = tag.startsWithLet;
      state.startsWithLetSquareBracket = tag.startsWithLetSquareBracket;
      state.startsWithFunctionOrClass = tag.startsWithFunctionOrClass;
    }
    return state;
  }

  reduceTemplateElement(node) {
    return new RawToken(node.rawValue);
  }

  reduceThisExpression(/* node */) {
    return t('this');
  }

  reduceThrowStatement(node, { expression }) {
    return seq(t('throw'), expression, semiOp());
  }

  reduceTryCatchStatement(node, { body, catchClause }) {
    return seq(t('try'), body, catchClause);
  }

  reduceTryFinallyStatement(node, { body, catchClause, finalizer }) {
    return seq(t('try'), body, catchClause || empty(), t('finally'), finalizer);
  }

  reduceYieldExpression(node, { expression }) {
    if (node.expression == null) return t('yield');
    return objectAssign(seq(t('yield'), p(node.expression, getPrecedence(node), expression)), { containsIn: expression.containsIn });
  }

  reduceYieldGeneratorExpression(node, { expression }) {
    return objectAssign(seq(t('yield'), t('*'), p(node.expression, getPrecedence(node), expression)), { containsIn: expression.containsIn });
  }

  reduceDirective(node) {
    let delim = node.rawValue.match(/(^|[^\\])(\\\\)*"/) ? '\'' : '"';
    return seq(t(delim + node.rawValue + delim), semiOp());
  }

  reduceVariableDeclaration(node, { declarators }) {
    return seq(t(node.kind), commaSep(declarators));
  }

  reduceVariableDeclarationStatement(node, { declaration }) {
    return seq(declaration, semiOp());
  }

  reduceVariableDeclarator(node, { binding, init }) {
    let containsIn = init && init.containsIn && !init.containsGroup;
    if (init) {
      if (init.containsGroup) {
        init = paren(init);
      } else {
        init = markContainsIn(init);
      }
    }
    return objectAssign(init == null ? binding : seq(binding, t('='), init), { containsIn });
  }

  reduceWhileStatement(node, { test, body }) {
    return objectAssign(seq(t('while'), paren(test), body), { endsWithMissingElse: body.endsWithMissingElse });
  }

  reduceWithStatement(node, { object, body }) {
    return objectAssign(
      seq(t('with'), paren(object), body),
      { endsWithMissingElse: body.endsWithMissingElse });
  }
}

module.exports = MinimalCodeGen;