Tidy tyvar OccNames in TcTyClDecl

[ghc-hetmet.git] / compiler / basicTypes / DataCon.lhs

diff --git a/compiler/basicTypes/DataCon.lhs b/compiler/basicTypes/DataCon.lhs
index 3450602..8829128 100644 (file)
--- a/compiler/basicTypes/DataCon.lhs
+++ b/compiler/basicTypes/DataCon.lhs
@@ -260,6 +260,9 @@ data DataCon
                -- [This is a change (Oct05): previously, vanilla datacons guaranteed to
                --  have the same type variables as their parent TyCon, but that seems ugly.]
 
+       -- INVARIANT: the UnivTyVars and ExTyVars all have distinct OccNames
+       -- Reason: less confusing, and easier to generate IfaceSyn
+
        dcEqSpec :: [(TyVar,Type)],     -- Equalities derived from the result type, 
                                        -- *as written by the programmer*
                -- This field allows us to move conveniently between the two ways