docs: function parseIfStatement(node) {
          var test, consequent, alternate;
  
          expectKeyword('if');
  
          expect('(');
  
          test = parseExpression();
  
          expect(')');
  
          consequent = parseStatement();
  
          if (matchKeyword('else')) {
              lex();
              alternate = parseStatement();
          } else {
              alternate = null;
          }
  
          return node.finishIfStatement(test, consequent, alternate);
      }