RFC: Change what assert does on error

[Richard (Rikki) Andrew Cattermole]

On 05/07/2025 4:18 AM, Jonathan M Davis wrote:
> On Friday, July 4, 2025 6:48:21 AM Mountain Daylight Time Richard (Rikki) Andrew Cattermole via Digitalmars-d wrote:
>> Contracts are a good example of this, they are inherently recoverable
>> because they are in a functions API, they are not internal unrecoverable
>> situations!
> 
> Not really, no. The point of contracts is to find bugs in the calling code,
> because the function has requirements about how it must be called, and it's
> considered a bug if the function is called with arguments that do not meet
> those requirements. The assertions are then compiled out in release mode,
> because they're simply there to find bugs, not to be part of the function's
> API.
> 
> On the other hand, if a function is designed to treat the arguments as user
> input or is otherwise designed to defend itself against bad input rather
> than treating bad arguments as a bug, then it should be using Exceptions and
> not contracts. The fact that they're thrown is then essentially part of the
> function's API, and they need to be left in in release builds.
> 
> By definition, assertions are only supposed to be used to catch bugs in a
> program, not for defending against bad input. They're specifically there to
> catch bugs rather than protect against bad input, whereas Exceptions are
> left in permanently, because they're there to protect against bad user input
> or problems in the environment which are not caused by bugs in the program.
> 
> - Jonathan M Davis

This is exactly my point. They are tuned wrong.

They are currently acting as an internal detail of a function, and that 
has no business being exposed at the function API level.

Other programmers do not need this information.

What they need is logic level criteria for a function to work.

The purpose of contracts first and foremost is to document the 
requirements of a called function and they are currently not succeeding 
at this job, because their focus is on internal details rather than 
external.