c++ - Is function overloading by reference allowed when there is no ambiguity? -

consider following code:

#include <iostream>  void foo(int m); void foo(int &k);  int main() {     foo(5); // ok, because there no ambiguity      int m = 5;     //foo(m); // compile-time error, because of ambiguity     foo(m + 0); // ok, because it's expression of type int , not object's lvalue }  void foo(int m) {     std::cout << "by value\n"; } void foo(int &k) {     std::cout << "by reference\n"; } 

i understand introduces ambiguity foo(m), allowed, when expression of type int (or can converted int)?

i have tried find standard reference on this, yet no luck.

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^{disclaimer: note it's not duplicate of function overloading based on value vs. const reference. const references different can assigned rvalues, opposite "ordinary", non-const references.}

yes, allowed.

there no rule prevent overload.

[c++14: 13.1/1]: not function declarations can overloaded. cannot overloaded specified here. [..]

[c++14: 13.1/2]: (blah blah lots of exceptions not including case)

it extremely limiting language prohibit function overloads may ambiguous in scenarios calls, , no reason might add!