Bug 22210 – std.meta.allSatisfy in mutual recursion classes cannot be compiled

The following code works with dmd 2.096.1 but does not work with dmd 2.097.0. Digger shows that it was introduced by the commit 406e51c68 in druntime. run.dlang.io: https://run.dlang.io/is/Ot8L6n ```dlang:sample.d import std.meta : allSatisfy; enum isHashable(T) = __traits(compiles, () { T.init; } ); class A { static if (isHashable!B) {} } class B { static if (isHashable!C) {} } class C { static if (allSatisfy!(isHashable, int, B)) {} } void main() {} ``` 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, int, B)` error instantiating onlineapp.d(19): instantiated from here: `allSatisfy!(isHashable, int, B)` onlineapp.d(14): Error: template instance `onlineapp.isHashable!(C)` error instantiating onlineapp.d(9): Error: template instance `onlineapp.isHashable!(B)` error instantiating ``` I use the following commands to search for the commit that introduces this issue: ```console $ cat bisect.ini bad = master @ v2.097.0 good = master @ v2.096.1 reverse = false tester = dmd -i -run sample.d $ dub run digger -- bisect bisect.ini ... digger: c717e2eda7063a583ada54182f3016139a50a61f is the first bad commit commit c717e2eda7063a583ada54182f3016139a50a61f Author: Andrei Alexandrescu <[email protected]> Date: Tue May 4 15:45:09 2021 -0400 druntime: Simplify anySatisfy, allSatisfy, maxAlignment diff --git a/druntime b/druntime index 5cfc074f7..406e51c68 160000 --- a/druntime +++ b/druntime @@ -1 +1 @@ -Subproject commit 5cfc074f73d2087841e66871cd859946ba14003a +Subproject commit 406e51c68c94a65e383da5aaa500c17d0a9c4d0e ``` - If we use `isHashable!int && isHashable!B` instead of `allSatisfy!(isHashable, int, B)`, it works with both of dmd 2.096.1 and dmd 2.097.0. - If we use `isHashable!B && isHashable!int` instead of `allSatisfy!(isHashable, int, B)`, it is the case of Issue 22184 (does not work with both versions)

I found that it works if I changed the order of declaration to B, C and A as follows. Therefore the source of this issue is issue 20443, I guess. ```dlang:sample.d import std.meta : allSatisfy; enum isHashable(T) = __traits(compiles, () { T.init; } ); class B { static if (isHashable!C) {} } class C { static if (allSatisfy!(isHashable, int, B)) {} } class A { static if (isHashable!B) {} } void main() {} ```

@tom-tan created dlang/druntime pull request #3618 "Fix issue 22210 - Revert #3459 and #3463" mentioning this issue: - Add test for issue 22210 https://github.com/dlang/druntime/pull/3618

dlang/druntime pull request #3618 "Fix issue 22210 - Partially revert #3459 and #3463" was merged into stable: - 9d0a29a896b924030b5aaec92b89ad82437865fd by Tomoya Tanjo: Add test for issue 22210 https://github.com/dlang/druntime/pull/3618