`return const` parameters make `inout` obsolete

Zach the Mystic via Digitalmars-d digitalmars-d at puremagic.com
Tue Mar 17 08:55:58 PDT 2015

On Tuesday, 17 March 2015 at 12:02:15 UTC, Nick Treleaven wrote:
> On 16/03/2015 14:17, Zach the Mystic wrote:
>> char* fun(return const char* x);
>> Compiler has enough information to adjust the return type of 
>> `fun()` to
>> that of input `x`. This assumes return parameters have been 
>> generalized
>> to all reference types. Destroy.
> inout can be used for local variables too.

Yeah that might be a use for it.

inout(T*) fun(inout(T*) t) {
   inout(T*) x = t;
   return x;
T* gun(return const T* t) {
   const(T*) x = t;
   return x;

To be fully viable, `return` would have to be secretly recorded 
as part of the `x's type, so that the compiler could forgive 
returning it to a non-const. But the compiler should probably 
track that `x` is copied from `t` anyway, so that it can verify 
`return t` when it returns `x`, and the same information would be 
used to forgive `x's constness.

But yeah, there might still be a use for `inout`.

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