Move Constructor Syntax

[Timon Gehr]

On 10/15/24 21:29, Arafel wrote:
> 
> I had a look at it before posting, and according to it [1] (my bold):
> 
>  > A Move Constructor for struct S is declared as:
>  >
>  >   ```d
>  >      this(S s) { ... }
>  >   ```
>  >
>  > [...]
>  >
>  > A _Move Constructor_ is a struct member constructor that moves, 
> rather than copies, the argument corresponding to its first parameter 
> into the object to be constructed. **The argument is invalid after this 
> move**, and is not destructed.

You are right assuming move constructors work as shown in DIP1040. 
However, I think this design is not really workable, and I think Manu is 
arguing from a position of assuming that the argument needs to remain 
valid and will be destroyed by default.

A benefit of `=this(ref S)` syntax or similar is that it supports the 
design where the argument is not destructed without additional language 
features to elide the destructor call, and without a special case where 
destructor elision may be unexpected given the syntax.

However, I think it either has to leave the argument in a valid state or 
explicit moves have to blit `.init` over the argument after calling the 
move constructor.