[cfe-dev] RFC: clang-tidy readability check to reduce clutter: unnecessary use of auto and ->

[Richard via cfe-dev]

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Hello tidy programmers,

There seems to be a certain breed of programmer that once having
learned a new feature of C++ intends to get out their new feature
hammer and bang on everything in sight.

Case in point:

N2541 <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2541.htm>
introduced auto and the trailing return type syntax.

Now people are using auto and -> on function signatures where the
return type is stated explicitly anyway.  This results in code like:

auto main() -> int
{
  return 0;
}

Srsly?  Is this really improving anything over

int main()
{
  return 0;
}

To me this is introducing unnecessary clutter and isn't the reason why
auto and -> for function return types were introduced.

I would like to propose a clang-tidy readability check that turns the
former into the latter when the return type doesn't use anything that
needs auto.  In other words, this code would be left alone:

template <typename T, typename U>
auto add(T x, U y) -> decltype(x + y)
{
  return x + y;
}

There is one note in N2541 that states how the new syntax eliminates
an ambiguity with this example:

auto f() -> int (*)[4];
// function returning a pointer to array[4] of int,
// not function returning array[4] of pointer to int.

This seems to be another case that should be left unchanged.

Proposed check name: readability-redundant-auto-return-type

What are your thoughts?
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