Core, shadowing type variable names

There is a problem with unique type variables in some bindings when 
generating Core.

I found the error in Text/ParserCombinators/ReadP.hcr (generated with 
the -O0 flag).


The error occurs at line 825 in ReadP.hcr:

-----
                    %case ds %of (wild::GHCziBase.ZMZN GHCziBase.Char)
                      {GHCziBase.ZC
                       (c::GHCziBase.Char) (cs::GHCziBase.ZMZN GHCziBase.Char) 
->
                         zddmzgzg @ GHCziBase.Char @ (GHCziBase.ZMZN 
GHCziBase.Char)
                         (TextziParserCombinatorsziReadP.char c) (scan cs);
-----



If we look at the definition of zddmzgzg, line 732, we see what the 
problem is:

-----
   zddmzgzg :: %forall a b . (%forall b . (a ->
                                           TextziParserCombinatorsziReadP.P b)
                                          -> TextziParserCombinatorsziReadP.P b)
                             ->
                             (%forall b . (b -> TextziParserCombinatorsziReadP.P 
b) ->
                                          TextziParserCombinatorsziReadP.P b)
                             ->
                             %forall b . (b -> TextziParserCombinatorsziReadP.P b) 
->
                                         TextziParserCombinatorsziReadP.P b = 
...
-----


The second time b is bound it shadows the first binding. Maybe there is 
a missing tidyType on the binding types?


If we at line 54 in ReadP.hs change
 newtype ReadP a = R (forall b . (a -> P b) -> P b)
to
 newtype ReadP a = R (forall z . (a -> P z) -> P z)
we get the correct type definition in the generated Core code:

-----
   zddmzgzg :: %forall a b . (%forall zz . (a ->
                                            TextziParserCombinatorsziReadP.P zz)
                                           -> TextziParserCombinatorsziReadP.P 
zz)
                             ->
                             (%forall zz . (b -> TextziParserCombinatorsziReadP.P 
zz) ->
                                           TextziParserCombinatorsziReadP.P zz)
                             ->
                             %forall zz . (b -> TextziParserCombinatorsziReadP.P 
zz) ->
                                          TextziParserCombinatorsziReadP.P zz = 
...
-----


This problem can also be found in Lex.hcr at line 1479.



Sincerely,
 Tobias