I consider Unique as user-defined affine types— half of what makes up a linear type. Clean and Mercury are both mentioned in: https://en.m.wikipedia.org/wiki/S

I consider Unique as user-defined affine types— half of what makes up a linear type. Clean and Mercury are both mentioned in: https://en.m.wikipedia.org/wiki/Substructural_type_system https://en.m.wikipedia.org/wiki/Substructural_type_system