Revert "Revert "Work around existing bug exposed by mixin caching.""
Revert "Revert "Work around existing bug exposed by mixin caching.""

This breaks typechecking for some types of mixins, such as `sub () is
nodal { }`.

This reverts commit 771b95438e4059e50fd1153e4e611e9f000c0569.

tony-o/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,labster/rakudo,tbrowder/rakudo,salortiz/rakudo,tony-o/rakudo,nbrown/rakudo,MasterDuke17/rakudo,softmoth/rakudo,rakudo/rakudo,tony-o/rakudo,salortiz/rakudo,labster/rakudo,salortiz/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tony-o/rakudo,softmoth/rakudo,salortiz/rakudo,tbrowder/rakudo,rakudo/rakudo,nbrown/rakudo,labster/rakudo,nbrown/rakudo,rakudo/rakudo,tbrowder/rakudo,tbrowder/rakudo,softmoth/rakudo,labster/rakudo,rakudo/rakudo,tony-o/rakudo,nbrown/rakudo,tbrowder/rakudo,nbrown/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,rakudo/rakudo,MasterDuke17/rakudo,nbrown/rakudo,tony-o/rakudo,softmoth/rakudo,labster/rakudo,softmoth/rakudo,salortiz/rakudo