Exception specification in ˋtypedefˋ completely forbidden or only at toplevel?

Question

In C++14 Sec 15.4;2 it is stated, that ... An exception-specification shall not appear in a typedef declaration or alias-declaration.

That means the following is forbidden:

typedef void (*fn)(int) noexcept;

But does the the wording shall not appear mean the token noexcept cannot appear anywhere in a typedef declaration?

For instance are these both are forbidden as well?

typedef void (*fn1)(void (*)(int) noexcept);
typedef decltype(std::declval<void (*)(int)noexcept>()) fn2;

These both try to define a type fn1 and fn2 being able to point to a function that takes a pointer to a function taking an int and returning nothing while promising to never throw an exception.

So in my examples the exception-specification is not applied to the toplevel type fn1 resp. fn2 that are introduced by typedef but to the parameters these function may receive.

So should I take 15.4;2 verbatim and therefore my both examples are invalid? Or is only application to a type-definition forbidden and my examples are correct?

Answer 1

It's the whole thing.

Quoting the full wording of [except.spec]/p2 from C++11 and C++14:

An exception-specification shall appear only on a function declarator for a function type, pointer to function type, reference to function type, or pointer to member function type that is the top-level type of a declaration or definition, or on such a type appearing as a parameter or return type in a function declarator. An exception-specification shall not appear in a typedef declaration or alias-declaration.

Perhaps it's not completely clear, but I think it's sufficiently so: you can use an exception specification on a function declaration, including in a parameter or return type on a function declaration … but not in an alias declaration.

This wording has been completely removed in C++17; noexcept is part of the type system now.