The following code works with dmd 2.096.1 (uses sumtype via dub) but does not work since dmd 2.097.0 (uses sumtype or std.sumtype). I'm not sure it is a regression of std.sumtype or dmd. I tentatively set the `Component` field to `phobos`. run.dang.io - (sumtype): https://run.dlang.io/is/IiGESU - (std.sumtype): https://run.dlang.io/is/j8rqve ```dlang import std.sumtype; class A { SumType!B type; } class B { SumType!C fields; } class C { SumType!(B, int) type; } ``` Error message: ```console /dlang/dmd/linux/bin64/../../src/druntime/import/core/internal/traits.d(191): Error: forward reference of variable `isHashable` /dlang/dmd/linux/bin64/../../src/phobos/std/meta.d(842): Error: template instance `core.internal.traits.allSat!(isHashable, const(B), const(int))` error instantiating /dlang/dmd/linux/bin64/../../src/phobos/std/sumtype.d(771): instantiated from here: `allSatisfy!(isHashable, const(B), const(int))` onlineapp.d(15): instantiated from here: `SumType!(B, int)` /dlang/dmd/linux/bin64/../../src/druntime/import/core/internal/traits.d(191): Error: template instance `std.sumtype.pred!(const(C))` error instantiating /dlang/dmd/linux/bin64/../../src/phobos/std/meta.d(842): instantiated from here: `allSat!(isHashable, const(C))` /dlang/dmd/linux/bin64/../../src/phobos/std/sumtype.d(771): instantiated from here: `allSatisfy!(isHashable, const(C))` onlineapp.d(10): instantiated from here: `SumType!(C)` /dlang/dmd/linux/bin64/../../src/druntime/import/core/internal/traits.d(191): Error: template instance `std.sumtype.pred!(const(B))` error instantiating /dlang/dmd/linux/bin64/../../src/phobos/std/meta.d(842): instantiated from here: `allSat!(isHashable, const(B))` /dlang/dmd/linux/bin64/../../src/phobos/std/sumtype.d(771): instantiated from here: `allSatisfy!(isHashable, const(B))` onlineapp.d(5): instantiated from here: `SumType!(B)` ``` Notes: - It works if `A` is not available - It works if `C` has a field whose type is `SumType!B` rather than `SumType!(B, int)`
It works if we declare the classes in the following order: C, A and B. run.dlang.io: https://run.dlang.io/is/qRsc7e
I reduced the above code as follows: run.dlang.io: https://run.dlang.io/is/VZtiPO ```dlang class A { static if (isHashable!B) {} } class B { static if (isHashable!C) {} } class C { static if (isHashable!B && isHashable!int) {} } enum isHashable(T) = __traits(compiles, () { T.init; } ); void main(){} ``` - It compiles successfully if `isHashable` checks `T t;` rather than `T.init;`
I fixed the issue title and the `Component` section because it is a issue of dmd rather than std.sumtype.
Sorry, I found that I made an inappropriate reproducible code for the issue. The first example fails both of dmd 2.096.1 and dmd 2.097.0. Please close this issue as invalid.
Even if it's not a regression, it's still a valid issue. I'll change the category to "normal" and leave it open for now. Possibly related to issue 20443.
I close this issue because the first example now works with dmd 2.100.2. However, the reduced example still does not work. I will make a comment about the reduced case to the issue 20443 instead of keep open this issue.