Bug 4423 considers the case of enum structs where all values are explicitly specified; it requires a particular opCmp signature. The case of enum structs when values are NOT specified is even more problematic. struct Foo { int x; } enum Bar : Foo { a, b } For this to work, it is required that Foo supports: * implicit cast from 0 to Foo. * a .max property * + 1 * and opCmp of the correct signature. I think this is a useless feature, and should simply be dropped. Currently, the test case gives some unhelpful error messages, containing __error and no line number: crash.d(3): Error: cannot implicitly convert expression (0) of type int to Foo66 99 Error: no property 'max' for type 'Foo6699' crash.d(3): Error: Integer constant expression expected instead of (__error) == (__error)
The same thing happens if you do something like enum Foo : string { a, b } q.d(3): Error: cannot implicitly convert expression (0) of type int to string Error: no property 'max' for type 'string' q.d(3): Error: Integer constant expression expected instead of (__error) == (__error) So, it's not really struct-specific. It affects all types which can't be implicitly assigned 0. It would probably be simplest to require that enums must either be values or they must be primitive types other than arrays, or maybe outright require that they be integral values (I question the usefulness of using bool or floating point enums without specifying their values).
In git-head, diagnostic has been improved. (In reply to Don from comment #0) > struct Foo { int x; } > enum Bar : Foo { a, b } test.d(2): Error: cannot implicitly convert expression (0) of type int to Foo (In reply to Jonathan M Davis from comment #1) > The same thing happens if you do something like > > enum Foo : string { a, b } test.d(1): Error: cannot implicitly convert expression (0) of type int to string
Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/4cf455e6c5d686aa239300f3f6e955f6e8ceac66 fix Issue 7477 - Enum structs without specified values