Changes between Version 4 and Version 5 of TypeFunctionsSyntax

Timestamp:

12/28/06 11:30:17 (6 years ago)

Author:

chak

Comment:

--

TypeFunctionsSyntax

@@ -30 +30 @@
 We add type declarations to class declarations and instance declarations by a new field, of type `[LTyClDecl]`, to both `TyClDecl.ClassDecl` (known by the field name `tcdATs`) and `TyClDecl.InstDecl`.  For classes, this new field contains values constructed from `TyData`, `TyFunction`, and `TySynonym`, whereas for instances, we only have `TyData` and `TySynonym`.  This is due to (a) `TyData` representing both signatures and definitions of associated data types (whereas the two are split into `TyFunction` and `TySynonym` for associated synonyms) and (b) associated synonyms having default definitions, which associated data types do not possess.
 
+== Representation of equational constraints ==
+
+Equational constraints are parsed into a new variant of `HsPred`, called `HsEqualP`.  Renaming (by `RnTypes.rnPred`) and kind checking (by `TcHsType.kc_pred`) is straight forward.  Afterwards, `HsPred` is desugared into `TypeRep.PredType`, where the wellformedness of equational constraints in type contexts is further tested by `TcMType.check_pred_ty`; in particular, we require the type arguments to be rank 0.
+
 == Type tags ==