Copy Constructor DIP and implementation

[rmc]

On Wednesday, 19 September 2018 at 00:05:15 UTC, Jonathan M Davis 
wrote:
> On Tuesday, September 18, 2018 10:58:39 AM MDT aliak via 
> Digitalmars-d- announce wrote:
>> This will break compilation of current code that has an 
>> explicit copy constructor, and the fix is simply to add the 
>> attribute @implicit.
>
> In that case, why not just use a transitional compiler switch? 
> Why force everyone to mark their copy constructors with 
> @implicit forever? The whole point of adding the attribute was 
> to avoid breaking existing code.
>
> - Jonathan M Davis

What about a command-line switch that just detects copy 
constructors?

LLVM 8 supposedly has a new feature which breaks compatibility 
for casts from float -> int:

Floating-point casts—converting a floating point number to an 
integer by discarding the data after the decimal—has been 
optimized, but in a way that might cause problems for developers 
who rely on undefined behavior around this feature. Clang has a 
new command-line switch to detect this issue.

Could we do copy-constructors in a similar way?