diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md index ff31d95..a6f8b85 100644 --- a/CppCoreGuidelines.md +++ b/CppCoreGuidelines.md @@ -2873,6 +2873,38 @@ Declaring `main` (the one global `main` of a program) `void` limits portability. * The compiler should do it * If the compiler doesn't do it, let tools flag it +### F.46: Return `T&` from assignment operators. + +##### Reason + +The convention for operator overloads (especially on value types) is for +`operator=(const T&)` to perform the assignment and then return (non-const) +`*this`. This ensures consistency with standard library types and follows the +principle of "do as the ints do." + +##### Note + +Historically there was some guidance to make the assignment operator return +`const T&`. This was primarily to avoid code of the form `(a=b)=c` - such code +is not common enough to warrant violating consistency with standard types. + +##### Example + + class Foo + { + public: + ... + Foo& operator=(const Foo& rhs) { + // Copy members. + ... + return *this; + } + }; + +##### Enforcement + +This should be enforced by tooling by checking the return type (and return +value) of any assignment operator. ### F.50: Use a lambda when a function won't do (to capture local variables, or to write a local function)