• Q. Schroll (22/22) Jun 20 2020 Entering dmd -preview=h shows this list:
• Stanislav Blinov (15/19) Jun 20 2020 Ostensibly, it should enable binding of rvalues (temporaries) as

Q. Schroll <qs.il.paperinik gmail.com> writes:

Entering dmd -preview=h shows this list:

   =all              list information on all upcoming language 
changes
   =dip25            implement [..] (Sealed references)
   =dip1000          implement [..] (Scoped Pointers)
   =dip1008          implement [..] ( nogc Throwable)
   =dip1021          implement [..] (Mutable function arguments)
   =fieldwise        use fieldwise comparisons for struct equality
   =markdown         enable Markdown replacements in Ddoc
   =fixAliasThis     when a symbol is resolved, check alias this 
scope before going to upper scopes
   =intpromote       fix integral promotions for unary + - ~ 
operators
   =dtorfields       destruct fields of partially constructed 
objects
   =rvaluerefparam   enable rvalue arguments to ref parameters
   =nosharedaccess   disable access to shared memory objects
   =in               in means scope const

While "implement <DIP link omitted>" do link to documents 
explaining details, I have no idea what `rvaluerefparam` does 
exactly. Is there an (online) resource where details to the 
others are given or linked?

Stanislav Blinov <stanislav.blinov gmail.com> writes:

On Saturday, 20 June 2020 at 14:36:25 UTC, Q. Schroll wrote:

 While "implement <DIP link omitted>" do link to documents 
 explaining details, I have no idea what `rvaluerefparam` does 
 exactly. Is there an (online) resource where details to the 
 others are given or linked?

Ostensibly, it should enable binding of rvalues (temporaries) as 
ref arguments for functions (a-la how in C++ temporaries bind to 
const T&), i.e.

Tea makeSomeTea() { /* ... */ }

void takeSomeTea(ref const Tea) { /* ... */ }

void main()
{
     takeSomeTea(makeSomeTea());
}

Without that switch, the above won't compile, because 
historically D disallowed such binding. Manu (among others) 
pushed for this to be possible, hence the switch. Though 
implementation, AFAICT, is still somewhere in the "under 
construction" territory, judging by Bugzilla.