[PATCH] D129835: [clang] adds a discardable attribute

[Christopher Di Bella via Phabricator via cfe-commits]

cjdb added a comment.

>> With [[discardable]] one just needs to push/pop at the extremes of a file (and if a future version of module maps supports global pragmas for a module, there too, but that's a discussion that requires a design doc).
>
> I understood that, I just don't think that's a good thing. This is basically an attribute that says "I know we said we wanted everything here to be nodiscard, but JUST KIDDING not this one!" which is not a very clean approach to writing headers.

@aaron.ballman Ugh, I've finally come up with a good use-case for `[[discardable]]`.

  class [[nodiscard]] iterator {
  public:
    // usual iterator stuff
  
    [[clang::discardable]] iterator operator++(int);
    [[clang::discardable]] iterator operator--(int);
  };

I hate it, but the alternative is to decorate everything else with `[[nodiscard]]` just to facilitate these two operators. It's a compelling use-case, but I'm not sure if it's compelling enough on its own. WDYT?
(I personally think that those two should be nodiscard, but `i++` is pervasive enough that it might never be practical to correct.)


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D129835/new/

https://reviews.llvm.org/D129835