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digitalmars.D.learn - Implicit casting of int enum members to int

reply Mike Bierlee <m.bierlee lostmoment.com> writes:
Consider the following code:

enum StringTypeEnumOne : string {
	bla = "bla"
}

enum StringTypeEnumTwo : string {
	bleh = "bleh"
}

enum IntTypeEnumOne : int {
	bla = 1
}

enum IntTypeEnumTwo : int {
	bleh = 2
}

public void main() {
	string[] strings = [StringTypeEnumOne.bla, 
StringTypeEnumTwo.bleh];
	int[] ints = [IntTypeEnumOne.bla, IntTypeEnumTwo.bleh];
}

When compiled the following compilation error is thrown:
src\app.d(19,16): Error: cannot implicitly convert expression 
(cast(IntTypeEnumOne)1) of type IntTypeEnumOne to IntTypeEnumTwo

The string members are implicitly cast just fine, however I also 
expected the members of the int enum to be cast implicitly 
because I explicitly defined the base type of the enum.

Is this a bug in D? Or is using an int as base type the same as 
having no base type at all?
Oct 02 2016
parent reply Jonathan M Davis via Digitalmars-d-learn writes:
On Sunday, October 02, 2016 18:31:11 Mike Bierlee via Digitalmars-d-learn 
wrote:

 Consider the following code:

 enum StringTypeEnumOne : string {
   bla = "bla"
 }

 enum StringTypeEnumTwo : string {
   bleh = "bleh"
 }

 enum IntTypeEnumOne : int {
   bla = 1
 }

 enum IntTypeEnumTwo : int {
   bleh = 2
 }

 public void main() {
   string[] strings = [StringTypeEnumOne.bla,
 StringTypeEnumTwo.bleh];
   int[] ints = [IntTypeEnumOne.bla, IntTypeEnumTwo.bleh];
 }

 When compiled the following compilation error is thrown:
 src\app.d(19,16): Error: cannot implicitly convert expression
 (cast(IntTypeEnumOne)1) of type IntTypeEnumOne to IntTypeEnumTwo

 The string members are implicitly cast just fine, however I also
 expected the members of the int enum to be cast implicitly
 because I explicitly defined the base type of the enum.

 Is this a bug in D? Or is using an int as base type the same as
 having no base type at all?


It looks like a bug. In theory, when you create an array literal like that,
it should choose the common type of all of the values in it (and result in a
compilation error if that doesn't work), though I recall there being bugs
with that and classes (with it just selecting the type of the last value
IIRC), so it doesn't entirely surprise me if you're seeing bugs with it. If
both of the values were from the same enum, I would expect that the
resulting type would be a dynamic array of that enum type, and the
initialization of ints would then fail, but with them being different enum
types with the base type of int, it really should result in int[], which
would succeed. So, it does look like you've found a bug, and the fact that
it works with enum types with a base type of string but not int is
particularly bizarre.

- Jonathan M Davis
Oct 03 2016
parent reply Mike B Johnson <Mikey Ikes.com> writes:
On Monday, 3 October 2016 at 09:21:37 UTC, Jonathan M Davis wrote:

 [...]


Is this bug ever going to be fixed?

I can't do

enum X : Y
{
    a = 1
}

because 1 is not implicitly convertible to Y, even though Y is 
aliased to an int so it should be.
Jun 04 2017
next sibling parent "H. S. Teoh via Digitalmars-d-learn" <digitalmars-d-learn puremagic.com> writes:
On Mon, Jun 05, 2017 at 01:23:22AM +0000, Mike B Johnson via
Digitalmars-d-learn wrote:

 On Monday, 3 October 2016 at 09:21:37 UTC, Jonathan M Davis wrote:

 [...]


 
 Is this bug ever going to be fixed?
 
 I can't do
 
 enum X : Y
 {
    a = 1
 }
 
 because 1 is not implicitly convertible to Y, even though Y is aliased
 to an int so it should be.


Works for me:

	alias Y = int;
	enum X : Y {
		a = 1
	}

Please post a minimal example that doesn't work.


T

-- 
Try to keep an open mind, but not so open your brain falls out. -- theboz
Jun 04 2017
prev sibling parent Mike Bierlee <m.bierlee lostmoment.com> writes:
On Monday, 5 June 2017 at 01:23:22 UTC, Mike B Johnson wrote:

 On Monday, 3 October 2016 at 09:21:37 UTC, Jonathan M Davis 
 wrote:
 Is this bug ever going to be fixed?


I've filed this issue under 
https://issues.dlang.org/show_bug.cgi?id=16586 a while ago, seems 
to have not been picked up yet.
Jun 05 2017