Is there any way to specify that a variable, member or parameter can't be null?

On Monday, 20 June 2022 at 17:48:48 UTC, Antonio wrote:

Depends on the type. Basic types can't be null. Pointers and classes can always be null, though you could wrap them in a custom library type that doesn't allow them to be null. Dynamic arrays and associative arrays can be null, but it's equivalent to them being empty, so you can still use them like normal. You can pass a struct as a ref parameter, which passes it by reference but it's still typed as a plain struct, so it can't be null.

On Monday, 20 June 2022 at 17:48:48 UTC, Antonio wrote:

You can use an invariant if it's a member of an aggregate but be warned that these are only checked at the boundaries of public member functions.

On Monday, 20 June 2022 at 19:08:32 UTC, max haughton wrote:

I'm using preconditions when calling functions

auto readByCredentiasl(CredentialsDTO credentials)
in (credentials !is null)
in (credentias.username !is null)
...
{
 ...
}

But it's runtime validation, not formally validated by compiler.