The original intent of 13.3.3.1p4 is to describe how to apply the requirement in 12.3p4 that: 4 – At most one user-defined conversion (constructor or conversion function) is implicitly applied to a single value. Before defect 84, 13.3.3.1p4 was almost purely informative: 4 – In the context of an initialization by user-defined conversion (i.e., when … Read more
Automatic casts are almost always evil. If there were a cast to const char *, a std::string could be also automatically cast to other pointer types and that could lead to hard to find bugs. There is the c_str() method that returns const char * so you can still achieve what you need. Also, the … Read more
Short answer: User-defined implicit conversions do not work on interfaces. Don’t try to make it work. Find another solution to your type system problem. Long answer: This is a deliberate decision of the C# design team. The principle is that when you are making a conversion involving an interface you want to preserve referential identity; … Read more
The actual names of the things you describe is not implicit and explicit assignment but : Copy-initialization : T x = a; Direct-initialization : T x(a); They are not equivalent, most notably in contexts where a conversion is required, for example when T is of class type and a is of a different type (see … Read more
This can depend on a variety of factors – the operating system’s regional settings, the current user’s language and dateformat settings. By default, Windows uses US English, and the user’s settings are US English and MDY. But here are some examples to show how this can change. User is using BRITISH language settings: — works: … Read more
The compiler has an implicit conversion from a constant expression to various primitive types (so long as the value is within the appropriate range), but here the expression isn’t constant – it’s just an int expression. It’s pretty much the same as: short s; s = CallSomeMethodReturningInt32(); as far as the compiler is concerned. There … Read more
Implicit is the correct term, and the section is 6.26.2 in the spec, and this must be a duplicate question (or so one would think; this is stable behavior). The linked question also answers that the expected type must be a function. I’ll go out on a limb and say that when overloaded, applicability is … Read more
Update: Explicit move should not be needed in modern compiler versions. Core DR 1579 changed the rules so that the return value will be treated as an rvalue even when the types are not the same. GCC 5 implements the new rule, for C++11 as well as C++14. Original answer: This is not a limitation … Read more
The reason it does not just work is that implicit type conversions (that is, via constructors) do not apply during template argument deduction. But it works if you make the outside operator a friend since then the type T is know, allowing the compiler to investigate what can be casted to make the arguments match. … Read more
I believe clang is correct here. We can see from the draft C++ standard section 6.4.2 The switch statement that this involves a contextually implicit conversion. Paragraph 2 says (*emphasis mine going forward): The condition shall be of integral type, enumeration type, or class type. If of class type, the condition is contextually implicitly converted … Read more