Guidelines for named return values (#5178)

Author: ernestognw

GUIDELINES.md

@@ -131,6 +131,13 @@ In addition to the official Solidity Style Guide we have a number of other conve
   abstract contract AccessControl is ..., {
   ```
 
+* Return values are generally not named, unless they are not immediately clear or there are multiple return values.
+
+  ```solidity
+  function expiration() public view returns (uint256) { // Good
+  function hasRole() public view returns (bool isMember, uint32 currentDelay) { // Good
+  ```
+
 * Unchecked arithmetic blocks should contain comments explaining why overflow is guaranteed not to happen. If the reason is immediately apparent from the line above the unchecked block, the comment may be omitted.
 
 * Custom errors should be declared following the [EIP-6093](https://eips.ethereum.org/EIPS/eip-6093) rationale whenever reasonable. Also, consider the following: