On 03/24/2018 03:03 AM, Jonathan M Davis wrote:
On Saturday, March 24, 2018 01:37:10 Nick Sabalausky via Digitalmars-d
wrote:
Why require the callee's author to add boilerplate? Just do it for all
ref params that are given an rvalue.
Because if the point of the function accepting its argument by ref is
because it's going to mutate the argument, then it makes no sense for it to
accept rvalues,
1. That *isn't* always the core point of a function which takes a
non-const ref argument.
2. It's the caller who decides whether or not the ref-result is needed,
not the callee.
3. The frequent recurring complaints about no rvalue references are a
testament that this is too common a use-case for the current "manually
insert temporaries" workaround to be satisfactory.
4. If the whole point of disallowing rvalue references is to prevent
accidents due to callers not realizing a param is being passed by ref
(as it sounds like you're suggesting), then it's nothing but a broken
half-solution, because it fails to provide that safety (and thus fails
its own charter) when that same caller, once again not realizing a param
is ref, passes an *lvalue* without expecting it to change. *If* the
problem we want to solve here really is making sure a caller knows when
a param is ref, we've failed, and the only way to actually accomplish it
is the C# approach: Require callers to mark their ref args with "ref"
and raise an error when they don't.
