We are left with following problem, upon which TcT provides the
certificate YES(?,O(n^1)).

Strict Trs:
  { foldl#3(x2, Nil()) -> x2
  , foldl#3(x16, Cons(x24, x6)) -> foldl#3(Cons(x24, x16), x6)
  , main(x1) -> foldl#3(Nil(), x1) }
Obligation:
  innermost runtime complexity
Answer:
  YES(?,O(n^1))

The input was oriented with the instance of 'Small Polynomial Path
Order (PS,1-bounded)' as induced by the safe mapping

 safe(foldl#3) = {1}, safe(Nil) = {}, safe(Cons) = {1, 2},
 safe(main) = {}

and precedence

 main > foldl#3 .

Following symbols are considered recursive:

 {foldl#3}

The recursion depth is 1.

For your convenience, here are the satisfied ordering constraints:

              foldl#3(Nil(); x2) > x2                            
                                                                 
  foldl#3(Cons(; x24,  x6); x16) > foldl#3(x6; Cons(; x24,  x16))
                                                                 
                       main(x1;) > foldl#3(x1; Nil())            
                                                                 

Hurray, we answered YES(?,O(n^1))