text: /**
   * @fileoverview Disallows unnecessary `return await`
   * @author Jordan Harband
   */
  "use strict";
  
  const astUtils = require("../ast-utils");
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  const message = "Redundant use of `await` on a return value.";
  
  module.exports = {
      meta: {
          docs: {
              description: "disallow unnecessary `return await`",
              category: "Best Practices",
              recommended: false // TODO: set to true
          },
          fixable: null,
          schema: [
          ]
      },
  
      create(context) {
  
          /**
           * Reports a found unnecessary `await` expression.
           * @param {ASTNode} node The node representing the `await` expression to report
           * @returns {void}
           */
          function reportUnnecessaryAwait(node) {
              context.report({
                  node: context.getSourceCode().getFirstToken(node),
                  loc: node.loc,
                  message
              });
          }
  
          /**
           * Determines whether a thrown error from this node will be caught/handled within this function rather than immediately halting
           * this function. For example, a statement in a `try` block will always have an error handler. A statement in
           * a `catch` block will only have an error handler if there is also a `finally` block.
           * @param {ASTNode} node A node representing a location where an could be thrown
           * @returns {boolean} `true` if a thrown error will be caught/handled in this function
           */
          function hasErrorHandler(node) {
              let ancestor = node;
  
              while (!astUtils.isFunction(ancestor) && ancestor.type !== "Program") {
                  if (ancestor.parent.type === "TryStatement" && (ancestor === ancestor.parent.block || ancestor === ancestor.parent.handler && ancestor.parent.finalizer)) {
                      return true;
                  }
                  ancestor = ancestor.parent;
              }
              return false;
          }
  
          /**
           * Checks if a node is placed in tail call position. Once `return` arguments (or arrow function expressions) can be a complex expression,
           * an `await` expression could or could not be unnecessary by the definition of this rule. So we're looking for `await` expressions that are in tail position.
           * @param {ASTNode} node A node representing the `await` expression to check
           * @returns {boolean} The checking result
           */
          function isInTailCallPosition(node) {
              if (node.parent.type === "ArrowFunctionExpression") {
                  return true;
              }
              if (node.parent.type === "ReturnStatement") {
                  return !hasErrorHandler(node.parent);
              }
              if (node.parent.type === "ConditionalExpression" && (node === node.parent.consequent || node === node.parent.alternate)) {
                  return isInTailCallPosition(node.parent);
              }
              if (node.parent.type === "LogicalExpression" && node === node.parent.right) {
                  return isInTailCallPosition(node.parent);
              }
              if (node.parent.type === "SequenceExpression" && node === node.parent.expressions[node.parent.expressions.length - 1]) {
                  return isInTailCallPosition(node.parent);
              }
              return false;
          }
  
          return {
              AwaitExpression(node) {
                  if (isInTailCallPosition(node) && !hasErrorHandler(node)) {
                      reportUnnecessaryAwait(node);
                  }
              }
          };
      }
  };
  