Default() and subrange types

[Der schöne Günther 323]

Consider the following code:

 

program Project1;

uses
	System.SysUtils;
type
	TSubRange = 1..10;
var
	subRange: TSubRange;
begin
	subRange := Default(TSubRange);
	Assert(subRange = Low(TSubRange)); // subRange should be 1, but is 0
end.

I was under the impression, that the default value of TSomeRange would be 1 and not 0, a value that can neither be set at compile time, nor at runtime.

Documentation of System.Default - RAD Studio API Documentation is non-existent.

 

Documentation about subrange types (Simple Types (Delphi) - RAD Studio) is a bit more helpful: 

Quote

The ordinality of each value in a subrange is preserved from the base type. (...)  Values do not wrap around the beginning or end of a subrange, even if the base is an integer or character type; incrementing or decrementing past the boundary of a subrange simply converts the value to the base type. (...) Hence, while: I := 100 produces an error, I := 99; Inc(I); assigns the value 100 to I (unless compiler range-checking is enabled).

In my case, it doesn't matter whether range checking at runtime is enabled or disabled. Default(TSubRange) seems to gloss over the definition of TSubRange, thinks "Hey, it's a byte" and just outputs 0.

 

My question:

- Is this valid behaviour? Has it changed? I am using Delphi 11.1

- Are there possibly any other caveats with subrange types? Maybe just not use them at all?

Edited Wednesday at 12:17 PM by Der schöne Günther

[Lajos Juhász 311]

It is not (yet) addressed in Delphi 12.2 it still defaults to 0 instead of 1.

[Anders Melander 1894]

26 minutes ago, Lajos Juhász said:

It is not (yet) addressed in Delphi 12.2 it still defaults to 0 instead of 1.

Don't expect it to be "fixed". The best you can hope for is that it is documented.

 

The current behavior is consistent with class initialization; If you have the same field in a class and create a new instance, then the ordinal value of the field will be zero - as expected.

[DelphiUdIT 209]

For each data whose value I need to know for sure before using it, I perform an assignment operation of a certain value at the creation of any "parent" or at the creation of the application.
I had some problems with the "default" in the past, so I equipped myself and I do it like this.

I know it's probably excessive, but so far I haven't had any issues.