On 11.07.2019 11:58, J. Gareth Moreton wrote:
Done!
Thank you for your work!
BTW, your note in the issue report is very misleading:
https://bugs.freepascal.org/view.php?id=33603#c117162.
> The idea behind "is" and "as" is that they are the sole exception to
the rule and will return False and raise an error respectively if the
enum is out of bounds.
IS/AS are not an exception of the rule - after a long discussion we
settled down that if IS/AS is applied on a value of the same enumeration
type:
var
MyEnumValue: TEnumValue;
begin
if MyEnumValue is TEnumValue then
// ...
end;
the compiler will expect that the result is always true. (It doesn't
have to check for invalid values.)
When I read the following sentence:
> If the value falls within a hole, then it will pass - currently only
in Delphi mode though. FPC mode won't allow it.
I think you mixed up "normal enums" and "enums with holes" and so the
note in the issue report doesn't make any sense.
----
The conclusion is:
1.) IS/AS works reliably only on valid values on the left side of the
operator. (Like any other function/intrinsic/operator in FPC.)
2.) If an invalid value is to be expected, IS/AS must be executed on an
ordinal value (Integer, SmallInt, ...) before assigning it to the
enumeration value. It cannot be executed on the resulting enumeration
value to check its validity.
3.) IS/AS can be used also on "enumerations with holes". In this respect
only the low/high bounds are checked, not the holes inside the valid range.
4.) IS/AS can be also used on ordinal types:
- 4a.) (MyInt64Value is Integer) is a reasonable check if MyInt64Value
is in Integer range.
- 4b.) (MyIntegerValue is Int64) is not reasonable (Integer falls
always into Int64 range) and will always return True and can/will be
optimized by the compiler to return a True constant.
Ondrej
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