lintStgRhs :: StgRhs -> LintM (Maybe Type)   -- Just ty => type is exact

lintStgRhs (StgRhsClosure _ _ _ _ _ [] expr)
  = lintStgExpr expr
lintStgRhs :: StgRhs -> LintM (Maybe Type)
lintStgRhs (StgRhsClosure _ _ _ _ _ [] expr)
  = lintStgExpr expr
lintStgRhs (StgRhsClosure _ _ _ _ _ [] expr)
  = lintStgExpr expr