[PATCH] D26038: [coroutines] Sema: Allow co_return all by itself.

[Gor Nishanov via Phabricator via llvm-commits]

GorNishanov added a comment.

In https://reviews.llvm.org/D26038#613723, @EricWF wrote:

> @GorNishanov Ping. Can you provide some clarity on this?


Starting from P0057R2, wording stated: 8.4.4/1: A function is a coroutine if it contains a coroutine-return-statement (6.6.3.1), an await-expression (5.3.8), a yield-expression (5.21), or a range-based for (6.5.4) with co_await.

Before the Big Kona Keyword Rename of 2015, you had to have 'await' or 'yield' for a function to a be a coroutine. Now, since, co_return is only usable in coroutines, have a co_return also triggers the coroutine processing.

  task<int> f() {
    Do something (no await here) 
    #if 0 // not yet implemented
       something with await
    #endif
    co_return 42;
  }

This is not the reason to have co_return, but, once we have it, I think using it as one of the indicators that a function is a coroutine is a reasonable approach.

Cheers,
Gor


https://reviews.llvm.org/D26038