@trust is an encapsulation method, not an escape

[Vladimir Panteleev via Digitalmars-d]

On Friday, 6 February 2015 at 08:58:05 UTC, Walter Bright wrote:
> On 2/6/2015 12:31 AM, Kagamin wrote:
>> On Thursday, 5 February 2015 at 23:39:39 UTC, Walter Bright 
>> wrote:
>>>  static void trustedMemcopy(T[] dest, T[] src) @trusted
>>>  {
>>>    assert(src.length == dest.length);
>>>    memcpy(dest.ptr, src.ptr, src.length * T.sizeof);
>>>  }
>>
>> Should be enforce: assert doesn't guard against malicious 
>> usage.
>
> Cue my endless attempts to explain the difference between input 
> errors and logic errors :-(

So which one is it?

On one hand, it is clearly a logic error - passing arrays of 
different length is clearly a program bug.

On the other hand, this is a library function, and as you said, 
we can't know how it's going to be used - so the check has to be 
unconditional.