Let's say I have a noncopyable class and I want to provide a customized error message when users try to copy.
struct A {
A() = default;
private:
[[deprecated("customized message")]]
A(const A&);
[[deprecated("customized message")]]
A& operator=(const A&);
};
I cannot use =delete for them, because compiler would only complain they are deleted. So I tried the transitional way: private non-defined functions.
Compiler will show
warning: 'A::A(const A&)' is deprecated: customized message [-Wdeprecated-declarations]
It works but not that good, because the word deprecated sounds like allowed-but-discouraged rather than disallowed simply.
My another try is
struct Customized_Message {
Customized_Message() = default;
Customized_Message(const Customized_Message&) = delete;
Customized_Message& operator=(const Customized_Message&) = delete;
};
struct A : Customized_Message {
A() = default;
};
<source>:17:11: error: use of deleted function 'A::A(const A&)'
17 | A b = a;
| ^
<source>:11:8: note: 'A::A(const A&)' is implicitly deleted because the default definition would be ill-formed:
11 | struct A : Customized_Message {
| ^
<source>:11:8: error: use of deleted function 'Customized_Message::Customized_Message(const Customized_Message&)'
<source>:8:5: note: declared here
8 | Customized_Message(const Customized_Message&) = delete;
| ^~~~~~~~~~~~~~~~~~
It works but looks not elegant ([Edit] because the message is not short, and compiler will replicate it as above).
Is there a better way to provide a customized error message? Thank you.
