addBinder :: CSEnv -> Id -> (CSEnv, Id)
addBinder (CS cs in_scope sub) v
| not (v `elemInScopeSet` in_scope) = (CS cs (extendInScopeSet in_scope v) sub, v)
- | isId v = (CS cs (extendInScopeSet in_scope v') (extendVarEnv sub v v'), v')
+ | isIdVar v = (CS cs (extendInScopeSet in_scope v') (extendVarEnv sub v v'), v')
| otherwise = WARN( True, ppr v )
(CS emptyUFM in_scope sub, v)
-- This last case is the unusual situation where we have shadowing of