add missing deduction guide for inplace_stop_callback - #2289
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[stopcallback.inplace.general] declares a deduction guide so that
`inplace_stop_callback cb{token, fn};` deduces the callback type.
stdexec did not provide it, so class template argument deduction
failed. Add the guide and a test.
Fixes NVIDIA#1420
ericniebler
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Sep 28, 2026
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/ok to test d728ebf |
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thanks! and welcome to the project @kwy404 |
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The standard declares a deduction guide for
inplace_stop_callback(stopcallback.inplace.general):stdexec did not declare it, so
inplace_stop_callback cb{token, fn};failed to compile. The constructor is a template over its own initializer type, so the implicit guide cannot deduce the callback type (MSVC: "error C2641: cannot deduce template arguments for 'stdexec::inplace_stop_callback'").This adds the guide right after the class, plus a test in
test_concepts_stop_tokens.cppthat checks the deduced type.Fixes #1420
Tested locally with MSVC 14.44 (Debug): the new test fails to compile without the fix and passes with it, and the rest of
test.stdexecpasses too (test_any.cppwas left out of the local build because this MSVC version hits an internal compiler error on it, on main as well). clang-format reports no changes on the touched files.