[cfe-dev] defaulted default constructor with initializer

[Richard Smith]

On Thu, Apr 16, 2015 at 10:16 AM, Kal <b17c0de at gmail.com> wrote:

>  Consider this code:
>
> class A {
> public:
>   struct I {
>     int i = 0;
>   };
>   A(I i = {}) {}
> };
>
> With clang 3.6 this doesn't compile:
> 4 : error: cannot use defaulted default constructor of 'I' within 'A'
> outside of member functions because 'i' has an initializer
>
> But if I change the code to
>
> class A {
> public:
>   struct I {
>     int i = 0;
>     I() {}
>   };
>   A(I i = {}) {}
> };
>
> then the code compiles. Why is this so? Aren't these equivalent?
>

They're not equivalent. The implicit constructor for A::I also has a
deduced exception specification, and computing that exception specification
requires the initializer for 'A::i' to have already been parsed.
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