Can I use always emplace to replace insert for single element insertion?

Question

I was wondering if it is OK to always use emplace to replace insert when inserting a single element into a STL container, like set, unordered_set?

From the signature, emplace is simpler and do not involve overloads. Is there any issue with stop using insert and use emplace all the time?

Note: there are SO questions asking about the difference between emplace and insert/push_back etc. (e.g. here, here, and here) I understand the difference, and it seems to me that emplace is better in every way. I just want to confirm if it's OK to deprecate insert.

Answer 1

There are some examples here that can be adapted to emplace and insert, showing when the behaviour may differ.

These examples may seem a bit artificial, so I'll give one that will hopefully appear less so:

#include <set>

template <typename T>
T id(T x) { return x; }

int main() {
    std::set<int(*)(int)> s;
    s.insert(id);       // OK
    s.emplace(id);      // error
    s.emplace(id<int>); // OK
}

insert can deduce the template parameter of id because it knows what type it wants. For emplace you get an error unless you explicitly specify.