• wolframw (15/15) Mar 14 2021 enum BoolEnum : bool { TestBool = false }
• Imperatorn (3/18) Mar 14 2021 May be a regression?
• Bastiaan Veelo (4/17) Mar 14 2021 Indeed: https://run.dlang.io/is/liSDBZ
• wolframw (16/26) Mar 16 2021 Thanks for the advice. I've since had a deeper look into this

wolframw <wolframw protonmail.com> writes:

enum BoolEnum   : bool   { TestBool   = false }
enum CharEnum   : char   { TestChar   = 'A' }
enum StringEnum : string { TestString = "Hello" }

pragma(msg, isBoolean!BoolEnum);       // true
pragma(msg, isSomeChar!CharEnum);      // true
pragma(msg, isSomeString!StringEnum);  // false

Why does isSomeString not return true for an enum with base type 
string while
other isX functions return true for enums with an according base 
type X?
Regarding whether enums should be considered by these functions, 
I can see the
case being made one of both ways (personally, I'd say they 
should), but in the
example above it seems that different rules are applied.

Imperatorn <johan_forsberg_86 hotmail.com> writes:

On Sunday, 14 March 2021 at 10:42:17 UTC, wolframw wrote:
 enum BoolEnum   : bool   { TestBool   = false }
 enum CharEnum   : char   { TestChar   = 'A' }
 enum StringEnum : string { TestString = "Hello" }

 pragma(msg, isBoolean!BoolEnum);       // true
 pragma(msg, isSomeChar!CharEnum);      // true
 pragma(msg, isSomeString!StringEnum);  // false

 Why does isSomeString not return true for an enum with base 
 type string while
 other isX functions return true for enums with an according 
 base type X?
 Regarding whether enums should be considered by these 
 functions, I can see the
 case being made one of both ways (personally, I'd say they 
 should), but in the
 example above it seems that different rules are applied.

May be a regression?

https://issues.dlang.org/show_bug.cgi?id=16573

Bastiaan Veelo <Bastiaan Veelo.net> writes:

On Sunday, 14 March 2021 at 16:09:39 UTC, Imperatorn wrote:
 On Sunday, 14 March 2021 at 10:42:17 UTC, wolframw wrote:
 enum BoolEnum   : bool   { TestBool   = false }
 enum CharEnum   : char   { TestChar   = 'A' }
 enum StringEnum : string { TestString = "Hello" }

 pragma(msg, isBoolean!BoolEnum);       // true
 pragma(msg, isSomeChar!CharEnum);      // true
 pragma(msg, isSomeString!StringEnum);  // false

 Why does isSomeString not return true for an enum with base 
 type string

 May be a regression?

 https://issues.dlang.org/show_bug.cgi?id=16573

Indeed: https://run.dlang.io/is/liSDBZ

It regressed in 2.079.1. Seems to be worth an issue report.

—Bastiaan.

wolframw <wolframw protonmail.com> writes:

On Sunday, 14 March 2021 at 16:30:47 UTC, Bastiaan Veelo wrote:
 On Sunday, 14 March 2021 at 16:09:39 UTC, Imperatorn wrote:
 On Sunday, 14 March 2021 at 10:42:17 UTC, wolframw wrote:
 [...]

 May be a regression?

 https://issues.dlang.org/show_bug.cgi?id=16573

 Indeed: https://run.dlang.io/is/liSDBZ

 It regressed in 2.079.1. Seems to be worth an issue report.

 —Bastiaan.

Thanks for the advice. I've since had a deeper look into this 
located the PR
that changed this behavior [1]. It seems this change was very 
much deliberate.
In the PR, Jonathan also makes some points that are very hard to 
disagree with.
So, perhaps the better solution would be to make isBoolean and 
isSomeChar (and
perhaps other functions that I didn't think of) return false for 
enums?

As a side note, isSomeChar returning true for enums is also what 
causes the
behavior demonstrated in Issue 21639 [2].

[1] https://github.com/dlang/phobos/pull/5291
[2] https://issues.dlang.org/show_bug.cgi?id=21639