CWG914 Value-initialization of array types

[jfbastien]

Migrating from https://isocpp.org/files/papers/P1018R18.html#issues
CWG914

Section: 7.6.1.4 [expr.type.conv] Status: extension Submitter: Gabriel Dos Reis Date: 10 June, 2009
Although value-initialization is defined for array types and the () initializer is permitted in a mem-initializer naming an array member of a class, the syntax T() (where is an array type) is explicitly forbidden by 7.6.1.4 [expr.type.conv] paragraph 2. This is inconsistent and the syntax should be permitted.

Rationale (July, 2009):

The CWG was not convinced of the utility of this extension, especially in light of questions about handling the lifetime of temporary arrays. This suggestion needs a proposal and analysis by the EWG before it can be considered by the CWG.

Although value-initialization is defined for array types and the () initializer is permitted in a mem-initializer naming an array member of a class, the syntax T() (where is an array type) is explicitly forbidden by 7.6.1.3 [expr.type.conv] paragraph 2. This is inconsistent and the syntax should be permitted.

Rationale (July, 2009): The CWG was not convinced of the utility of this extension, especially in light of questions about handling the lifetime of temporary arrays. This suggestion needs a proposal and analysis by the EWG before it can be considered by the CWG.

This has become a more severe inconsistency after we adopted Ville’s P0960 for C++20. Now it’s not only () that has this weird special-case restriction, it’s (a, b, c) too:

using X = int[];

X x{1, 2, 3}; // ok, int[3]

X y(1, 2, 3); // ok, int[3]

f(X{1, 2, 3}); // ok, int[3] temporary

f(X(1, 2, 3)); // error

Meeting: (notes) it is a defect, need a paper. David Stone trying to find a volunteer to write said paper. All in favor.