excessively long integer literal

[Robert DaSilva]

Ap Lee wrote:
> Hello,
> 
> I am trying to build some template struct for large integer values, and
> I realized there is something weird with the lexical interpretation of
> integer literals.
> 
> I have this code instantiating a LargeInt struct which, in this example,
> has a capacity of 256 bits:
> 
>   LargeInt!(256) v = 0xFFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF;
> 
> Under the hood, this assignment uses the opAssign overload I created for
> ulong. Obviously, ulong is only 64 bits in size, and only the lowest 64
> bits of the "v" variable get set to 1, while the upper bits remain at 0.
> 
> But there is something wrong. The compiler accepted this code, and it's
> silently wrong at runtime... I think the compiler should have rejected
> the integer literal.
> 
> What do you think?
> 
> Ap

The compiler should reject it, it rejects some literals
(0x1_0000_0000_0000_0000) with the error "large_int.d(5) integer
overflow". I think the reason it fail too is that it uses a very
simplistic overflow detection algorithm (if it's smaller than before, it
overflowed).