Typechecking the expression field is done with the correctly-named [`dumbcheck'`](https://github.com/CBMM/CBaaS/blob/43e6018047b9028c657d0ce0804d6e7eb40232f2/cbaas-lib/src/TypeCheck.hs#L29-L38) Implement a real typechecker.
Typechecking the expression field is done with the correctly-named
dumbcheck'Implement a real typechecker.