#include <vector> struct C { std::vector<int> v; decltype(v.begin()) begin() { return v.begin(); } decltype(v.end()) end() { return v.end(); } }; Clang++ has no problem, but MSVC 2013 gives the following error:
error C2228: left of '.begin' must have class/struct/union This is a known bug in VS2013, fixed in VS2015. The compiler will accept the code if you use a trailing return type instead.
struct C { std::vector<int> v; auto begin() -> decltype(v.begin()) { return v.begin(); } auto end() -> decltype(v.end()) { return v.end(); } }; As the bug report says, another work around is by using:
struct C { std::vector<int> v; decltype(std::declval<decltype(v)>().begin()) begin() { return v.begin(); } decltype(std::declval<decltype(v)>().end()) end() { return v.end(); } }; But as @BenVoigt points out in the comments, read this answer for why the trailing return type should be the preferred option.
Search the linked page for C++ decltype of class-member access incompletely implemented