have : m >>> 1 < m := Nat.div_lt_self hm (Nat.lt_succ_self 1)
case right.hdiv
m n : Nat
disjoint : m &&& n = 0
hm : m > 0
this : getBit (m &&& n) 0 = false
⊢ m >>> 1 + n >>> 1 = m >>> 1 ^^^ n >>> 1
case right.hdiv
m n : Nat
disjoint : m &&& n = 0
hm : m > 0
this✝ : getBit (m &&& n) 0 = false
this : m >>> 1 < m
⊢ m >>> 1 + n >>> 1 = m >>> 1 ^^^ n >>> 1