simp
case nil
Hknown : known [] = true
Hrefines : shapeRefines [] [] = true
⊢ shapeProd [] = 1

case cons
Hknown : known [] = true
head✝ : ℕ
tail✝ : List ℕ
Hrefines : shapeRefines (head✝ :: tail✝) [] = true
⊢ shapeProd (head✝ :: tail✝) = 1
case cons
Hknown : known [] = true
head✝ : ℕ
tail✝ : List ℕ
Hrefines : shapeRefines (head✝ :: tail✝) [] = true
⊢ shapeProd (head✝ :: tail✝) = 1