Function block_prop_writes 

pub fn block_prop_writes(
    def: &ComponentDef<'_>,
    block: Block<'_>,
    bound: &[Symbol],
) -> Vec<Symbol>

The PROPS a block writes — every one a mistake, since a prop is the parent’s value. bound are the names the block’s own header binds (an action’s parameters, a trigger’s values), which shadow a prop of the same name. The same walk as block_writes, so a verb that writes state is a verb that writes a prop.