Function lemma_u32_clearbit_not_bit_is_set 

pub broadcast proof fn lemma_u32_clearbit_not_bit_is_set(word: u32, b: int)

requires

0 <= b < 32,

ensures

!u32_bit_is_set(word & (!(1u32 << (b as usize))), b),

Clearing bit b makes that bit clear.