Replace = with {} initialization, even for auto declared variables

[N-Dekker]

Adjusted all code example according to ES.23: Prefer the {}-initializer syntax.

Note that this rule does allow using = with auto, but it appears more consistent to just use the {} syntax for auto as well.

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Honestly it's also OK for me to use = with auto, but then I would still like to know if the code examples are really meant to support using = with auto. Otherwise I think it's clearer to just use the {} syntax in the code examples (as proposed by this pull request).

[jwakely]

Personally I would prefer to rewrite (or remove) ES.23

The rules for {} initialization are simpler, more general, less ambiguous,

Those are all debatable.

and safer than for other forms of initialization.

Probably true.

Use = only when you are sure that there can be no narrowing conversions.

Or when you are writing generic templates and don't want to gratuitously reject code that actually works fine.

Almost every time we've used {} in the standard library spec, it's been a mistake and we've changed it.

[N-Dekker]

Thank you for your reply, @jwakely !

Note that this pull request still allows users to use = with auto declared variables. This PR only adjusts the examples, not the rules. And as far as I know, for auto declared variables, there is no semantic difference between brace-initialization and = initialization. So you might consider this a cosmetic PR. But it seems like using brace-initialization for auto variables (this PR) is in line with the current wording of ES.23: Prefer the {}-initializer syntax.

On the other hand, I would be very interested to see an update of ES.23 that would possibly make things clearer.

[hsutter]

Editors call: We haven't reviewed this because it's marked draft -- if it's ready for us to review it please mark it non-draft. Thanks!

[N-Dekker]

If I understand correctly, the Guidelines allow using = with auto, but they still prefer {} anyway. So then, would it be "preferable" to use {} for the examples, even with auto?

[N-Dekker]

When using the proposed {} for auto, some very old C++11 compilers might deduce res as an initializer_list<int>, instead of an int. For example, GCC 4.9.4: https://godbolt.org/z/G8G9v7qss Would that be a reason for rejecting this pull request?

In general, should the examples still have auto var = expr, instead of auto var {expr}, in order to support those old C++11 compilers?