I'm planning to merge this fix into the 4.0 release branch. Although not a regression, since <variant> is a new feature, it would still be nice to ship without this bug.
I'll merge these changes later today if there are no objections, and once all the bots pass. /Eric On Thu, Feb 9, 2017 at 12:01 PM, Eric Fiselier via cfe-commits < cfe-commits@lists.llvm.org> wrote: > Author: ericwf > Date: Thu Feb 9 13:01:22 2017 > New Revision: 294612 > > URL: http://llvm.org/viewvc/llvm-project?rev=294612&view=rev > Log: > Fix PR31916 - std::visit rejects visitors accepting lvalue arguments > > A static assertion was misfiring since it checked > is_callable<Visitor, decltype(__variant_alt<T>.value)>. However > the decltype expression doesn't capture the value category as > required. This patch applies extra braces to decltype to fix > that. > > Modified: > libcxx/trunk/include/variant > libcxx/trunk/test/std/utilities/variant/variant.visit/visit.pass.cpp > > Modified: libcxx/trunk/include/variant > URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/ > variant?rev=294612&r1=294611&r2=294612&view=diff > ============================================================ > ================== > --- libcxx/trunk/include/variant (original) > +++ libcxx/trunk/include/variant Thu Feb 9 13:01:22 2017 > @@ -578,7 +578,7 @@ private: > constexpr decltype(auto) operator()(_Alts&&... __alts) const { > __std_visit_exhaustive_visitor_check< > _Visitor, > - decltype(_VSTD::forward<_Alts>(__alts).__value)...>(); > + decltype((_VSTD::forward<_Alts>(__alts).__value))...>(); > return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor), > _VSTD::forward<_Alts>(__alts). > __value...); > } > > Modified: libcxx/trunk/test/std/utilities/variant/variant. > visit/visit.pass.cpp > URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/ > utilities/variant/variant.visit/visit.pass.cpp?rev= > 294612&r1=294611&r2=294612&view=diff > ============================================================ > ================== > --- libcxx/trunk/test/std/utilities/variant/variant.visit/visit.pass.cpp > (original) > +++ libcxx/trunk/test/std/utilities/variant/variant.visit/visit.pass.cpp > Thu Feb 9 13:01:22 2017 > @@ -283,9 +283,20 @@ void test_exceptions() { > #endif > } > > +// See http://llvm.org/PR31916 > +void test_caller_accepts_nonconst() { > + struct A {}; > + struct Visitor { > + void operator()(A&) {} > + }; > + std::variant<A> v; > + std::visit(Visitor{}, v); > +} > + > int main() { > test_call_operator_forwarding(); > test_argument_forwarding(); > test_constexpr(); > test_exceptions(); > + test_caller_accepts_nonconst(); > } > > > _______________________________________________ > cfe-commits mailing list > cfe-commits@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >
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