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[std-proposals] Inheriting Aggregate Initialization with using T::T

From: David Ledger <davidledger_at_[hidden]>
Date: Wed, 16 Feb 2022 02:39:50 +1100
Gday all!

In generic contexts it can be desirable to inherit the constructors of a
base class. Currently, this leads to broken code when the base class is
an aggregate, as it is no longer possible to initialize the aggregate
base's members.

An example:

struct A { A(int a, int b, int c){} };
struct B { int a, b, c; };
template <typename T>
struct N : T { using T::T; };
N<A> a{1, 2, 3}; // current: ok, inherits A::A
N<B> b{1, 2, 3}; // current: error, no constructor to inherit(and `N<B>` 
is now, not an aggregate)
// proposed: ok, elides the braces, and aggregate constructs
N<B> c{.a = 1, .b = 2, .c = 3}; // current: error, designated 
initializers cannot be used with a non-aggregate type 'Bar'
// proposed: ok, Foo's a, b, and c are initialized via the designated 
Proposal is here:

Received on 2022-02-15 15:39:56