Bug 23522 – Error message when enum type is not integral and a value lacks an initializer

If an `enum` has a type that is not numerical, every value must have an initializer: ```d enum X : string { a = "a", b // error } ``` The error message should be very specific (“`b` has no initializer and the underyling type is not integral”), but it is: ``` Error: no property `max` for type `string`, perhaps `import std.algorithm;` is needed? Error: incompatible types for `("a") + (1)`: `X` and `int` ```

semantics are more subtle, the increment from the previous value can work for non-integral types too: ``` struct FooInt { int i; auto opBinary(string op : "+")(int j) { return typeof(this)(i + j); } static @property FooInt max() { return typeof(this)(int.max); } } enum foolist { hi = FooInt(0), bye } ``` So you can only determine if the implicit value can be set by trying it.

@ntrel created dlang/dmd pull request #15588 "Improve error messages when enum member cannot be generated" fixing this issue: - Fix Issue 23522 - Error message when enum type is not integral and a value lacks an initializer https://github.com/dlang/dmd/pull/15588

With the PR, dmd will give introductory errors which should help the others make sense: enumstr.d(4): Error: cannot check `enumstr.X.b` value for overflow enumstr.d(1): Error: no property `max` for type `string`, perhaps `import std.algorithm;` is needed? enumstr.d(4): Error: cannot generate value for `enumstr.X.b` enumstr.d(4): Error: incompatible types for `("a") + (1)`: `X` and `int`

dlang/dmd pull request #15588 "Improve error messages when enum member cannot be generated" was merged into master: - fecd435f695f030ac4d1de548bb00e4f690dfacd by Nick Treleaven: Fix Issue 23522 - Error message when enum type is not integral and a value lacks an initializer https://github.com/dlang/dmd/pull/15588