[nem-en] Re: conversion of int to uint

[Michal Moskal]

On 2/23/06, Valient Gough <valient at gmail.com> wrote:
> Hi,
>
> I'm having trouble converting from an int to uint.  I have to convert
> to a common type because I need to apply a bit-field operation, and
> I'm constrained on the different types from external interfaces.
>
> My expectation was for something like this to work:
>
> def checkMask( mask, modes )
> {
>     if((mask :> uint) %& modes)
>         0;
>     else
>         ErrorCode.EACCES;
> }
>
> But that gives an error "System.Int32 is not a subtype of
> System.UInt32 [simple require]"

I guess the problem is that you need to write:

     if((mask :> uint) %& modes != 0)

There are two options:
  - either you pasted something else than you have in your sources
  - or there is some bug in the compiler that makes it produce such
junky error messages

Maybe you can post a self-contained example?

> So I searched around the nemerle site and didn't see anything. I tried
> other variations without success, and then I tried casting the uints
> to ints and got an interesting error:  "common super type of types
> [System.UInt32, int] is just `System.ValueType', please upcast one of
> the types to `System.ValueType' if this is desired
> "

We thought this would be hit mostly for System.Object, not
System.ValueType, where it makes more sense.

> So, I tried to force a conversion through ValueType:
>
> def checkMask( mask : ValueType , modes )
> {
>     if((mask :> uint) %& modes)
> ...
>
> That resulted in an ICE:
> error: internal compiler error: assertion failed in file
> generation/ILEmitter.n, line 778:
> Sulf.GenericNode::Access: failed to convert non-value type
> System.ValueType to a value type System.UInt32

This is an ICE on invalid code, so not that critical, but still a bug
that needs to be fixed, so please report.

--
   Michal Moskal,
   http://nemerle.org/~malekith/