if Condition expression can't have function?

[Steven Schveighoffer via Digitalmars-d]

On Fri, 25 Apr 2014 07:52:42 -0400, Nick Treleaven  
<ntrel-public at yahoo.co.uk> wrote:

> On 25/04/2014 08:29, Matthias Walter via Digitalmars-d wrote:
>>>      size_t find(T[] Array,T Element)
>>> >     {
>> find returns a size_t being a nonnegativ number.
>>
>>> >     return -1;
>> But here it returns -1.
>
> For size_t and uint 'dmd -w' seems to allow returning literal -1, but  
> with ubyte I get:
> Error: cannot implicitly convert expression (-1) of type int to ubyte
>
> Is this inconsistent or is there a reason for this?

It is inconsistent, but it's well known legacy based on C rules.

See Integer promotion and arithmetic conversions here:  
http://dlang.org/type

"Integer values cannot be implicitly converted to another type that cannot  
represent the integer bit pattern after integral promotion."

-Steve