Previously, every entry pair within the map would be copied. The reason
for this is subtle.
A std::map's internal entry type is defined as:
std::pair<const Key, Value>
but the loop was declaring it as:
std::pair<Key, Value>
These two types aren't synonymous with one another and so the compiler
is required to always perform a copy.
Using structured bindings avoids this (as would plain auto or correcting
the explicit type), while also allowing the use of more appropriate
names compared to first and second.
Lioncash
b15f595130