| 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')
| otherwise = WARN( True, ppr v )
(CS emptyUFM in_scope sub, v)
-- This last case is the unusual situation where we have shadowing of
-- a type variable; we have to discard the CSE mapping
| 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')
| otherwise = WARN( True, ppr v )
(CS emptyUFM in_scope sub, v)
-- This last case is the unusual situation where we have shadowing of
-- a type variable; we have to discard the CSE mapping