Assert expression specification needs to be updated

[dlangBugzillaToGithub]

Andrej Mitrovic (@AndrejMitrovic) reported this on 2020-04-29T01:46:28Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=20784

CC List

• Nick Treleaven (@ntrel)

Description

https://dlang.org/spec/expression.html#assert_expressions

> The first AssignExpression must evaluate to true. If it does not, an Assert Failure has occurred and the program enters an Invalid State.
> Undefined Behavior: Once in an Invalid State the behavior of the continuing execution of the program is undefined.

This in theory is true. And https://github.com/dlang/dmd/pull/6896, if merged, would actually make it really true. (It would be great if we got some progress on that PR). However see my next comment:

> Do not attempt to resume normal execution after an Assert Failure.

But then what is the point of `Runtime.extendedModuleUnitTester`? If an application enters an Invalid state then after the very first assertion failure it wouldn't make sense to continue running tests in other modules. But Druntime explicitly supports this feature..

> AssertExpression has different semantics if it is in a unittest or in contract.

The documentation doesn't actually list what the differences are. But maybe it should just link to the contracts page?

[dlangBugzillaToGithub]

nick (@ntrel) commented on 2023-03-31T12:20:10Z

> maybe it should just link to the contracts page?

Added link to precondition spec (among other tweaks):
https://github.com/dlang/dlang.org/pull/3572