Is it possible to replace "auto" with its deduced type, automatically, in C++?

Question

I've got a project I've been wrestling with for a while, which is almost ready for submission; but there have been a few previous coders who have contributed. Their code is great, but it doesn't satisfy the lint for the project this class is going to be submitted to; so, I'm spending some time cleaning it up.

One of the things this project forbids is the auto keyword. This is understandable, as a lot of people contribute to it, and they aren't all the most experienced so much as enthusiastic; so being explicit is a good thing.

There are quite a few autos in here. I remember that g++ -E would give me a file after the preprocessor was run, and it occurs to me that there's probably a way to do something similar with type specifiers.

Failing that, I'm using Qt Creator on a Linux box, which might also have a feature (kind of like "replace symbol under cursor") which I don't know about yet.

Is there anything that will allow me to automatically replace auto with its deduced type name, in a C++ file?

Answer 1

No, this is not possible in general, for multiple reasons.

Firstly, there are cases where auto refers to unnamed types, such as closure types of lambdas, etc.

struct {
    int data;
} stuff;

auto s = stuff{}; // What exactly is auto here, decltype(stuff) ?

auto l = []{}; // What exactly is auto here?
               // decltype([]{}) is not the same type,
               // and the closure type has no name.
               // ... should we auto-generate a typedef?

But even if you always had a usable type, how exactly should it be formatted?

// What exactly is auto here?
//  - std::uint8_t
//  - ::std::uint8_t
//  - uint8_t
//  - unsigned char
//  - unsigned __char
auto c = get_uint8();

// What exactly is auto here?
//  - std::string
//  - std::basic_string<char>
//  - std::basic_string<char, std::allocator<char>>
//  - std::__cxx11::basic_string<char, std::__cxx11::allocator<char>>
auto str = get_std_string();

Knowing which type to display to the user is an extremely difficult problem in C++. IDEs often have special cases to deal with this. For example, CLion may display std::basic_string<char> as string, but this is not an automated transformation.