Improve error reporting for non-rigid GADT matches

[ghc-hetmet.git] / compiler / hsSyn / HsExpr.lhs

diff --git a/compiler/hsSyn/HsExpr.lhs b/compiler/hsSyn/HsExpr.lhs
index 17a8c3f..66336b6 100644 (file)
--- a/compiler/hsSyn/HsExpr.lhs
+++ b/compiler/hsSyn/HsExpr.lhs
@@ -164,6 +164,8 @@ data HsExpr id
   -- Record update
   | RecordUpd   (LHsExpr id)
                 (HsRecordBinds id)
+--             (HsMatchGroup Id)  -- Filled in by the type checker to be 
+--                                -- a match that does the job
                 [DataCon]          -- Filled in by the type checker to the
                                    -- _non-empty_ list of DataCons that have
                                    -- all the upd'd fields
@@ -1018,10 +1020,10 @@ pp_dotdot = ptext (sLit " .. ")
 \begin{code}
 data HsMatchContext id  -- Context of a Match
   = FunRhs id Bool              -- Function binding for f; True <=> written infix
-  | CaseAlt                     -- Guard on a case alternative
-  | LambdaExpr                  -- Pattern of a lambda
-  | ProcExpr                    -- Pattern of a proc
-  | PatBindRhs                  -- Pattern binding
+  | CaseAlt                     -- Patterns and guards on a case alternative
+  | LambdaExpr                  -- Patterns of a lambda
+  | ProcExpr                    -- Patterns of a proc
+  | PatBindRhs                  -- Patterns in the *guards* of a pattern binding
   | RecUpd                      -- Record update [used only in DsExpr to
                                 --    tell matchWrapper what sort of
                                 --    runtime error message to generate]