Solidity — All About Runtime Errors

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This article is Part II of the “All About Errors” sub-series.

After looking at Compile Time errors in Part I (errors generated by the Solidity compiler), we will now look in Part II at runtime errors (errors generated at the time you interact with a contract deployed on a live network).

As we will see, 4 main types of errors can be generated in Solidity: Error(string), Panic(uint256), custom error and invalid. We will cover the rules and semantics of each of them in this article. Finally, we will have a quick glance at some potential predictions for the new error types that might be added to the Solidity programming language.

Table of content
- Common examples of errors in Solidity
- Types of Solidity errors
- Error(string) 
- Panic(uint256)
    - Panic Error - Example
    - Panic(uint256) error codes
- Custom Errors
    - How to define custom errors?
    - Why using custom errors over string errors?
    - Named parameters for custom errors
    - Natspec comments for custom errors
    - Custom Errors are part of the ABI
- Invalid
- Future Type of Errors in Solidity

Common examples of errors in Solidity

Many scenarios exist where a runtime error could occur among the Solidity code of a contract.

Some of the standard runtime errors related to Solidity include:

• When require() is called with the arguments which result as false.
• When creating a contract using the new keyword fails, and the process does not end properly.
• When a codeless (address.code.length) contract is targeted to an external function. (be aware of the isContract() culprit when it is running through a constructor)
• When ethers (= msg.value) is sent while calling a public getter (view) or pure method from a contract.
• when ethers (= msg.value ) are sent to a function in a contract that is not marked as payable .
• When a condition in an assert() is false.
• When a zero-initialised variable of function type is called.
• When a large or negative value is converted to an enum.
• When accessing an array in an index which is too big or…