coro: fix eager-conversion detection for clang >= 22#2664
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fmt::format is declared in <fmt/format.h>, not <fmt/core.h> on newer fmt (11/12). This file does not pull in format.h transitively, so it fails to build against newer fmt (e.g. homebrew on macOS CI). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Newer fmt (11/12) has no formatter for std::byte, so formatting a std::span<std::byte> via fmt/ranges.h is a hard error. Widen each element to an integer for the diagnostic message. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
detect_promise_return_object_eager_conversion() inferred "eager" from whether the promise was still alive at return-object conversion time (!!o.promise). clang >= 22 reordered the conversion to run before the promise destructor instead of after, so the promise is still alive at conversion even when conversion is deferred. The detector then wrongly reported eager, causing Expected/Optional coroutines to yield empty results (bad expected access / empty Optional unwrapped) on Mac CI, which builds with Homebrew LLVM. Detect the actual signal instead: whether the coroutine body already ran before the conversion, via a body_ran flag set in return_void. This is robust to the promise-dtor/conversion ordering and stays correct for genuinely-eager compilers (in eager mode the conversion precedes the body, and the return-object destructor nulls `object` so the later return_void is a safe no-op). Verified on clang 22 and AppleClang 17 at -O0..-O3 with the real eager/deferred branches. Fixes the shared detector used by Expected.h, Optional.h, and result/detail/result_promise.h, and satisfies the existing CoroutineTest contract (clang >= 17 => eager == false). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary: detect_promise_return_object_eager_conversion() inferred "eager" from whether the promise was still alive at return-object conversion time (!!o.promise). clang >= 22 reordered the conversion to run before the promise destructor instead of after, so the promise is still alive at conversion even when conversion is deferred. The detector then wrongly reported eager, causing Expected/Optional coroutines to yield empty results (bad expected access / empty Optional unwrapped) on Mac CI, which builds with Homebrew LLVM. Detect the actual signal instead: whether the coroutine body already ran before the conversion, via a body_ran flag set in return_void. This is robust to the promise-dtor/conversion ordering and stays correct for genuinely-eager compilers (in eager mode the conversion precedes the body, and the return-object destructor nulls `object` so the later return_void is a safe no-op). Verified on clang 22 and AppleClang 17 at -O0..-O3 with the real eager/deferred branches. Fixes the shared detector used by Expected.h, Optional.h, and result/detail/result_promise.h, and satisfies the existing CoroutineTest contract (clang >= 17 => eager == false). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> X-link: facebook/folly#2664 Reviewed By: Gownta Differential Revision: D109797717 Pulled By: afrind fbshipit-source-id: 9c6e99d61d941e685f3e9bb6015a1a9b8789b91c
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detect_promise_return_object_eager_conversion() inferred "eager" from
whether the promise was still alive at return-object conversion time
(!!o.promise). clang >= 22 reordered the conversion to run before the
promise destructor instead of after, so the promise is still alive at
conversion even when conversion is deferred. The detector then wrongly
reported eager, causing Expected/Optional coroutines to yield empty
results (bad expected access / empty Optional unwrapped) on Mac CI,
which builds with Homebrew LLVM.
Detect the actual signal instead: whether the coroutine body already ran
before the conversion, via a body_ran flag set in return_void. This is
robust to the promise-dtor/conversion ordering and stays correct for
genuinely-eager compilers (in eager mode the conversion precedes the
body, and the return-object destructor nulls
objectso the laterreturn_void is a safe no-op).
Verified on clang 22 and AppleClang 17 at -O0..-O3 with the real
eager/deferred branches. Fixes the shared detector used by Expected.h,
Optional.h, and result/detail/result_promise.h, and satisfies the
existing CoroutineTest contract (clang >= 17 => eager == false).
Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com