e></dt><dd><p>Checks if the declared type for `what` can be narrowed, based on the information about all assignments `what = rhs_i`. If an upper bound of `rhs_i` over ALL assignents `what = rhs_i` that exist in the program is a _strict_ subtype of lhs, `lhs`'s type can be narrowed to be that upper bound.</p></dd></dl><dl><dt class="spec type" id="type-violation_type"><a href="#type-violation_type" class="anchor"></a><code><span class="keyword">type</span> violation_type</code><code> = </code><table class="v