Solidity v0.6.11 adds inheritance to NatSpec comments, improves debugging data output and fixes some minor issues with opening up calldata for non-external functions.

Notable New Features

NatSpec Inheritance and on Events

NatSpec comments are a way to describe the behaviour of a function to end-users. It also allows to provide more detailed information to developers.

One regular use-case is that you document the behaviour of an interface and then implement the interface in a derived contract. Previously, you had to repeat the documentation in the derived contract. This is now obsolete: The compiler will automatically inherit the documentation of the base function if the derived function does not provide any NatSpec tag.

If you provide any of the tags (@param, @dev, …), then nothing will be inherited. The next release will provide a feature to explicitly inherit from a certain base also in that case, so stay tuned!

Furhermore, NatSpec is now supported on events.

// SPDX-License-Identifier: MIT
pragma solidity ^0.6.11;
interface Gathering {
  /// The address `participant` just registered for the gathering.
  event Registered(address participant);

  /// Registers `msg.sender` to take part in the gathering.
  function register() external;

contract MyGathering is Gathering {
  mapping(address => bool) public participants;

  function register() public override {
    participants[msg.sender] = true;
    emit Registered(msg.sender);

The derived contract MyGathering in the example code above will produce the following userdoc:

    "events": {
        "Registered(address)": {
            "notice": "The address `participant` just registered for the gathering."
    "kind": "user",
    "methods": {
        "register()": {
            "notice": "Registers `msg.sender` to take part in the gathering."
    "version": 1

Unit Denomination gwei

You can now use gwei as a unit denomination alongside wei, szabo, finney and ether:

reqire(msg.value >= 10 gwei);

Full Changelog

Language Features:

  • General: Add unit denomination gwei
  • Yul: Support linkersymbol builtin in standalone assembly mode to refer to library addresses.
  • Yul: Support using string literals exceeding 32 bytes as literal arguments for builtins.

Compiler Features:

  • NatSpec: Add fields kind and version to the JSON output.
  • NatSpec: Inherit tags from unique base functions if derived function does not provide any.
  • Commandline Interface: Prevent some incompatible commandline options from being used together.
  • NatSpec: Support NatSpec comments on events.
  • Yul Optimizer: Store knowledge about storage / memory after a := sload(x) / a := mload(x).
  • SMTChecker: Support external calls to unknown code.
  • Source Maps: Also tag jumps into and out of Yul functions as jumps into and out of functions.


  • NatSpec: Do not consider //// and /*** as NatSpec comments.
  • Type Checker: Disallow constructor parameters with calldata data location.
  • Type Checker: Do not disallow assigning to calldata variables.
  • Type Checker: Fix internal error related to using for applied to non-libraries.
  • Wasm backend: Fix code generation for for-loops with pre statements.
  • Wasm backend: Properly support both i32.drop and i64.drop, and remove drop.
  • Yul: Disallow the same variable to occur multiple times on the left-hand side of an assignment.
  • Yul: Fix source location of variable multi-assignment.

A big thank you to all contributors who helped make this release possible!

Download the new version of Solidity here.