diff options
| -rw-r--r-- | tests/generics/tfakecovariance.nim | 51 |
1 files changed, 48 insertions, 3 deletions
diff --git a/tests/generics/tfakecovariance.nim b/tests/generics/tfakecovariance.nim index 835acd9d3..bca285283 100644 --- a/tests/generics/tfakecovariance.nim +++ b/tests/generics/tfakecovariance.nim @@ -1,11 +1,56 @@ +template accept(x) = + static: assert(compiles(x)) + +template reject(x) = + static: assert(not compiles(x)) + type BaseObj = object of RootObj DerivedObj = object of BaseObj + NonDerivedObj = object Container[T] = object -proc doSomething(c: Container[BaseObj or DerivedObj]) = discard +var base: BaseObj +var derived: DerivedObj +var nonDerived: NonDerivedObj + +var baseContainer: Container[BaseObj] +var derivedContainer: Container[DerivedObj] +var nonDerivedContainer: Container[NonDerivedObj] + +# We can fake covariance by listing some specific derived types that +# will be allowed with our overload. This is not a real covariance, +# because there will be multiple instantiations of the proc, but for +# many purposes, it will suffice: + +proc wantsSpecificContainers(c: Container[BaseObj or DerivedObj]) = discard + +accept wantsSpecificContainers(baseContainer) +accept wantsSpecificContainers(derivedContainer) + +reject wantsSpecificContainers(nonDerivedContainer) +reject wantsSpecificContainers(derived) + +# Now, let's make a more general solution able to catch all derived types: + +type + DerivedFrom[T] = concept type A + var derived: ref A + var base: ref T = derived + +proc wantsDerived(x: DerivedFrom[BaseObj]) = discard + +accept wantsDerived(base) +accept wantsDerived(derived) + +reject wantsDerived(nonDerived) +reject wantsDerived(baseContainer) + +proc wantsDerivedContainer(c: Container[DerivedFrom[BaseObj]]) = discard + +accept wantsDerivedContainer(baseContainer) +accept wantsDerivedContainer(derivedContainer) -var t: Container[DerivedObj] -doSomething t +reject wantsDerivedContainer(nonDerivedContainer) |