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fixes #22936 This pull request improves the compiler's handling of generic type constraints, specifically for subtypes of generics, and adds a test to cover this behavior. The main changes are an enhancement to the type relationship logic in the compiler and a new test case for generic subtyping with `Future`. ### Compiler improvements for generic subtyping * Updated `typeRel` in `compiler/sigmatch.nim` to allow generic constraints (like `F: Future`) to accept not just direct instantiations but also descendants of the generic family, ensuring more flexible and correct overload resolution. Inheritance depth is now considered for overload ranking, making deeper descendants slightly less preferred, consistent with other inheritance-based matches. ### New test coverage * Added a test in `tests/typerel/t8905.nim` to verify that generic constraints correctly accept subtypes of `Future`, including a custom `B[T, E] = ref object of Future[T]` type, and that overloads like `take`, `takeMany`, and the macro `checkFutures` work as expected with these types.