[libcxx-commits] [PATCH] D112017: [libcxx][format] Fix how we handle char traits in formatter<string> and formatter<string_view>

[Arthur O'Dwyer via Phabricator via libcxx-commits]

Quuxplusone added inline comments.


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Comment at: libcxx/include/__format/formatter_string.h:148
+  _LIBCPP_HIDE_FROM_ABI auto
+  format(basic_string_view<_CharT, _Traits> __str, auto& __ctx)
+      -> decltype(__ctx.out()) {
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Aargh, I was gonna say "ship it" and then I noticed that... none of these `format` methods are marked `const`?! What's up with that?
https://en.cppreference.com/w/cpp/named_req/Formatter says:
> `formatter.format(arg, format_context)` [should work with] `formatter`, a **value** of type `Formatter`

What does "value" mean in this context? It probably doesn't mean "lvalue" or it would have said "lvalue," right? I suspect it means "(possibly const) lvalue or rvalue," in which case `format` should always be const-qualified. But then how does any of this //ever// work, today, given that we're not const-qualifying these `format` methods? Does this suddenly need further investigation?

Ping @Mordante — clarification please? (If @Mordante says "yeah this is all working as intended," then you can land this AFAIC.)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112017/new/

https://reviews.llvm.org/D112017