Solidity `error` type

Motivation

We want to support typed errors in a syntactically equivalent and convenient way like the programmer can define event types.

Example:

contract C {
	event HighestBidIncreased(address bidder, uint amount);
	error BiddingFailed(string reason);

	function bid() public payable {
		try attemptBid() {
			emit HighestBidIncreased(msg.sender, msg.value); // Triggering event
		} catch BiddingFailed(reason) {
			// handle error with given reason
		}
    }

	function attemptBid() {
		// require() should now support a custom secondary parameter to throw custom errors upon failed expectations.
		require(biddingPossible, BiddingFailed("Bidding impossible"));
	}
}

Syntax

errorDefinition
  : 'error' identifier eventParameterList AnonymousKeyword? ';' ;

Semantic

Errors can be instantiated wherever a variable of a type can be declared. Errors can NOT be instantiated like any arbitrary type, but instead only be used within require and revert.

Error types are ALWAYS publicly visible, i.e. they can not be made private.

Catching Errors

With the try-catch statement, you can already catch Error(string). This will be extended to catch errors by other structured types that were declared via the error keyword.

The fallback catch will also apply to error types that weren't matched.

Example:

contract C {
	event HighestBidIncreased(address bidder, uint amount);

	error BiddingFailed(string reason);
	error SomeOtherError(string text, uint value);

	function bid() public payable {
		try attemptBid() {
			emit HighestBidIncreased(msg.sender, msg.value); // Triggering event
		} catch BiddingFailed(string reason) {
			// handle error with given reason
		} catch SomeOtherError(string reason, uint value) {
			// handle other error with an additional value
		} catch Error(string message) {
			// handle classic error messages
		} catch (bytes data) {
			// parametrized default
		}
	}
}

The current `Error(string message)` type.

Currently, exceptions can be caught via catch Error(string text). This behaviour will be retained by providing the default error type Error.

Code Generation

Whatever ABI encoder is selected, this one will be used to encode/decode the error in require/revert/catch.

2.3 KiB Raw Blame History

Solidity error type