| 79 | | However, to implement superclass constraints, we need to have a `ClassInstEnv` (similar to the `InstEnv` and `FamInstEnv` right now). For a vanilla class, if we have `C t1 .. tn` in the constraint pool, we just can add all superclasses of `C` at the appropriate instance types. However, if `C` is a class family, we need to check whether there is a class-family instance `C r1 .. rn` and a substitution `theta`, such that `theta (C r1 .. rn) == C t1 .. tn`, then we can add the superclasses of `C r1 .. rn` at the instance types suggested by `theta`. This check for a class-family instance requires a function `lookupClassInstEnv` (similar to the current `lookupInstEnv` and `loookupFamInstEnv`). |
| | 79 | However, to implement superclass constraints, we need to have a `ClassInstEnv` (similar to the `InstEnv` and `FamInstEnv` right now). For a vanilla class, if we have `C t1 .. tn` in the constraint pool, we just can add all superclasses of `C` at the appropriate instance types. However, if `C` is a class family, we need to check whether there is a class-family instance `C r1 .. rn` and a substitution `theta`, such that `theta (C r1 .. rn) == C t1 .. tn`; if so, we can add the superclasses of `C r1 .. rn` at the instance types suggested by `theta`. This check for a class-family instance requires a function `lookupClassInstEnv` (similar to the current `lookupInstEnv` and `loookupFamInstEnv`). |
