r291955 - PR31606: Generalize our tentative DR resolution for inheriting copy/move

Hans Wennborg via cfe-commits cfe-commits at lists.llvm.org
Wed Jan 18 18:02:53 PST 2017


Merged in r292463.

Cheers,
Hans

On Tue, Jan 17, 2017 at 9:25 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> Yes, let's.
>
> On 17 Jan 2017 9:11 pm, "Hans Wennborg" <hans at chromium.org> wrote:
>
> What do you think; time to merge it?
>
> On Fri, Jan 13, 2017 at 1:21 PM, Richard Smith <richard at metafoo.co.uk>
> wrote:
>> I'd like to wait a bit to see how the dust settles on this one, but this
>> is
>> a bugfix for a previous bugfix for a standard change, and we've had
>> several
>> user complaints requesting that we fix the bug in the standard, so it's
>> probably a good change to get into Clang 4.
>>
>> ---------- Forwarded message ----------
>> From: Richard Smith via cfe-commits <cfe-commits at lists.llvm.org>
>> Date: 13 January 2017 at 12:46
>> Subject: r291955 - PR31606: Generalize our tentative DR resolution for
>> inheriting copy/move
>> To: cfe-commits at lists.llvm.org
>>
>>
>> Author: rsmith
>> Date: Fri Jan 13 14:46:54 2017
>> New Revision: 291955
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=291955&view=rev
>> Log:
>> PR31606: Generalize our tentative DR resolution for inheriting copy/move
>> constructors to better match the pre-P0136R1 behavior.
>>
>> Modified:
>>     cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>     cfe/trunk/lib/Sema/SemaOverload.cpp
>>     cfe/trunk/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p15.cpp
>>     cfe/trunk/test/CXX/dcl.decl/dcl.init/dcl.init.aggr/p1.cpp
>>     cfe/trunk/test/CXX/drs/dr16xx.cpp
>>     cfe/trunk/test/CXX/drs/dr19xx.cpp
>>     cfe/trunk/test/CXX/special/class.inhctor/p1.cpp
>>     cfe/trunk/test/CXX/special/class.inhctor/p3.cpp
>>     cfe/trunk/test/CXX/special/class.inhctor/p7.cpp
>>     cfe/trunk/test/SemaCXX/cxx11-inheriting-ctors.cpp
>>     cfe/trunk/test/SemaTemplate/cxx1z-using-declaration.cpp
>>
>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Jan 13
>> 14:46:54
>> 2017
>> @@ -3344,8 +3344,8 @@ def note_ovl_candidate : Note<"candidate
>>  def note_ovl_candidate_inherited_constructor : Note<
>>      "constructor from base class %0 inherited here">;
>>  def note_ovl_candidate_inherited_constructor_slice : Note<
>> -    "constructor inherited from base class cannot be used to initialize
>> from "
>> -    "an argument of the derived class type">;
>> +    "candidate %select{constructor|template}0 ignored: "
>> +    "inherited constructor cannot be used to %select{copy|move}1
>> object">;
>>  def note_ovl_candidate_illegal_constructor : Note<
>>      "candidate %select{constructor|template}0 ignored: "
>>      "instantiation %select{takes|would take}0 its own class type by
>> value">;
>>
>> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Fri Jan 13 14:46:54 2017
>> @@ -5944,6 +5944,28 @@ Sema::AddOverloadCandidate(FunctionDecl
>>        Candidate.FailureKind = ovl_fail_illegal_constructor;
>>        return;
>>      }
>> +
>> +    // C++ [over.match.funcs]p8: (proposed DR resolution)
>> +    //   A constructor inherited from class type C that has a first
>> parameter
>> +    //   of type "reference to P" (including such a constructor
>> instantiated
>> +    //   from a template) is excluded from the set of candidate functions
>> when
>> +    //   constructing an object of type cv D if the argument list has
>> exactly
>> +    //   one argument and D is reference-related to P and P is
>> reference-related
>> +    //   to C.
>> +    auto *Shadow =
>> dyn_cast<ConstructorUsingShadowDecl>(FoundDecl.getDecl());
>> +    if (Shadow && Args.size() == 1 && Constructor->getNumParams() >= 1 &&
>> +        Constructor->getParamDecl(0)->getType()->isReferenceType()) {
>> +      QualType P =
>> Constructor->getParamDecl(0)->getType()->getPointeeType();
>> +      QualType C = Context.getRecordType(Constructor->getParent());
>> +      QualType D = Context.getRecordType(Shadow->getParent());
>> +      SourceLocation Loc = Args.front()->getExprLoc();
>> +      if ((Context.hasSameUnqualifiedType(P, C) || IsDerivedFrom(Loc, P,
>> C)) &&
>> +          (Context.hasSameUnqualifiedType(D, P) || IsDerivedFrom(Loc, D,
>> P))) {
>> +        Candidate.Viable = false;
>> +        Candidate.FailureKind = ovl_fail_inhctor_slice;
>> +        return;
>> +      }
>> +    }
>>    }
>>
>>    unsigned NumParams = Proto->getNumParams();
>> @@ -6016,31 +6038,6 @@ Sema::AddOverloadCandidate(FunctionDecl
>>      }
>>    }
>>
>> -  // C++ [over.best.ics]p4+: (proposed DR resolution)
>> -  //   If the target is the first parameter of an inherited constructor
>> when
>> -  //   constructing an object of type C with an argument list that has
>> exactly
>> -  //   one expression, an implicit conversion sequence cannot be formed
>> if
>> C is
>> -  //   reference-related to the type that the argument would have after
>> the
>> -  //   application of the user-defined conversion (if any) and before the
>> final
>> -  //   standard conversion sequence.
>> -  auto *Shadow =
>> dyn_cast<ConstructorUsingShadowDecl>(FoundDecl.getDecl());
>> -  if (Shadow && Args.size() == 1 && !isa<InitListExpr>(Args.front())) {
>> -    bool DerivedToBase, ObjCConversion, ObjCLifetimeConversion;
>> -    QualType ConvertedArgumentType = Args.front()->getType();
>> -    if (Candidate.Conversions[0].isUserDefined())
>> -      ConvertedArgumentType =
>> -          Candidate.Conversions[0].UserDefined.After.getFromType();
>> -    if (CompareReferenceRelationship(Args.front()->getLocStart(),
>> -
>> Context.getRecordType(Shadow->getParent()),
>> -                                     ConvertedArgumentType,
>> DerivedToBase,
>> -                                     ObjCConversion,
>> -                                     ObjCLifetimeConversion) >=
>> Ref_Related) {
>> -      Candidate.Viable = false;
>> -      Candidate.FailureKind = ovl_fail_inhctor_slice;
>> -      return;
>> -    }
>> -  }
>> -
>>    if (EnableIfAttr *FailedAttr = CheckEnableIf(Function, Args)) {
>>      Candidate.Viable = false;
>>      Candidate.FailureKind = ovl_fail_enable_if;
>> @@ -10222,8 +10219,13 @@ static void NoteFunctionCandidate(Sema &
>>      return DiagnoseOpenCLExtensionDisabled(S, Cand);
>>
>>    case ovl_fail_inhctor_slice:
>> +    // It's generally not interesting to note copy/move constructors
>> here.
>> +    if (cast<CXXConstructorDecl>(Fn)->isCopyOrMoveConstructor())
>> +      return;
>>      S.Diag(Fn->getLocation(),
>> -           diag::note_ovl_candidate_inherited_constructor_slice);
>> +           diag::note_ovl_candidate_inherited_constructor_slice)
>> +      << (Fn->getPrimaryTemplate() ? 1 : 0)
>> +      << Fn->getParamDecl(0)->getType()->isRValueReferenceType();
>>      MaybeEmitInheritedConstructorNote(S, Cand->FoundDecl);
>>      return;
>>
>>
>> Modified:
>> cfe/trunk/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p15.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p15.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p15.cpp
>> (original)
>> +++ cfe/trunk/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p15.cpp Fri
>> Jan 13 14:46:54 2017
>> @@ -1,16 +1,16 @@
>>  // RUN: %clang_cc1 -std=c++11 -verify %s
>>
>> -struct B1 { // expected-note 2{{candidate}}
>> +struct B1 {
>>    B1(int); // expected-note {{candidate}}
>>  };
>>
>> -struct B2 { // expected-note 2{{candidate}}
>> +struct B2 {
>>    B2(int); // expected-note {{candidate}}
>>  };
>>
>>  struct D1 : B1, B2 { // expected-note 2{{candidate}}
>> -  using B1::B1; // expected-note 3{{inherited here}}
>> -  using B2::B2; // expected-note 3{{inherited here}}
>> +  using B1::B1; // expected-note {{inherited here}}
>> +  using B2::B2; // expected-note {{inherited here}}
>>  };
>>  D1 d1(0); // expected-error {{ambiguous}}
>>
>> @@ -35,7 +35,7 @@ namespace default_ctor {
>>      operator D&&();
>>    };
>>
>> -  struct A { // expected-note 4{{candidate}}
>> +  struct A { // expected-note 2{{candidate}}
>>      A(); // expected-note {{candidate}}
>>
>>      A(C &&); // expected-note {{candidate}}
>> @@ -47,7 +47,7 @@ namespace default_ctor {
>>      A(convert_to_D2); // expected-note {{candidate}}
>>    };
>>
>> -  struct B { // expected-note 4{{candidate}}
>> +  struct B { // expected-note 2{{candidate}}
>>      B(); // expected-note {{candidate}}
>>
>>      B(C &&); // expected-note {{candidate}}
>> @@ -66,9 +66,9 @@ namespace default_ctor {
>>      using B::operator=;
>>    };
>>    struct D : A, B {
>> -    using A::A; // expected-note 5{{inherited here}}
>> +    using A::A; // expected-note 3{{inherited here}}
>>      using A::operator=;
>> -    using B::B; // expected-note 5{{inherited here}}
>> +    using B::B; // expected-note 3{{inherited here}}
>>      using B::operator=;
>>
>>      D(int);
>> @@ -93,13 +93,13 @@ namespace default_ctor {
>>    }
>>
>>    struct Y;
>> -  struct X { // expected-note 2{{candidate}}
>> +  struct X {
>>      X();
>> -    X(volatile Y &); // expected-note {{constructor inherited from base
>> class cannot be used to initialize from an argument of the derived class
>> type}}
>> +    X(volatile Y &); // expected-note 3{{inherited constructor cannot be
>> used to copy object}}
>>    } x;
>> -  struct Y : X { using X::X; } volatile y; // expected-note
>> 2{{candidate}}
>> -  struct Z : Y { using Y::Y; } volatile z; // expected-note
>> 3{{candidate}}
>> expected-note 5{{inherited here}}
>> -  Z z1(x); // ok
>> -  Z z2(y); // ok, Z is not reference-related to type of y
>> +  struct Y : X { using X::X; } volatile y;
>> +  struct Z : Y { using Y::Y; } volatile z; // expected-note 4{{no known
>> conversion}} expected-note 2{{would lose volatile}} expected-note
>> 3{{requires 0}} expected-note 3{{inherited here}}
>> +  Z z1(x); // expected-error {{no match}}
>> +  Z z2(y); // expected-error {{no match}}
>>    Z z3(z); // expected-error {{no match}}
>>  }
>>
>> Modified: cfe/trunk/test/CXX/dcl.decl/dcl.init/dcl.init.aggr/p1.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/dcl.decl/dcl.init/dcl.init.aggr/p1.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/dcl.decl/dcl.init/dcl.init.aggr/p1.cpp (original)
>> +++ cfe/trunk/test/CXX/dcl.decl/dcl.init/dcl.init.aggr/p1.cpp Fri Jan 13
>> 14:46:54 2017
>> @@ -134,13 +134,13 @@ ExplicitDefaultedAggr eda2{};
>>
>>  struct DefaultedBase {
>>    int n;
>> -  DefaultedBase() = default; // expected-note 0+ {{candidate}}
>> -  DefaultedBase(DefaultedBase const&) = default; // expected-note 0+
>> {{candidate}}
>> -  DefaultedBase(DefaultedBase &&) = default; // expected-note 0+
>> {{candidate}}
>> +  DefaultedBase() = default;
>> +  DefaultedBase(DefaultedBase const&) = default;
>> +  DefaultedBase(DefaultedBase &&) = default;
>>  };
>>
>>  struct InheritingConstructors : DefaultedBase { // expected-note 3
>> {{candidate}}
>> -  using DefaultedBase::DefaultedBase; // expected-note 2 {{inherited
>> here}}
>> +  using DefaultedBase::DefaultedBase;
>>  };
>>  InheritingConstructors ic = { 42 }; // expected-error {{no matching
>> constructor}}
>>
>>
>> Modified: cfe/trunk/test/CXX/drs/dr16xx.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr16xx.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/drs/dr16xx.cpp (original)
>> +++ cfe/trunk/test/CXX/drs/dr16xx.cpp Fri Jan 13 14:46:54 2017
>> @@ -71,14 +71,14 @@ namespace dr1638 { // dr1638: yes
>>
>>  namespace dr1645 { // dr1645: 3.9
>>  #if __cplusplus >= 201103L
>> -  struct A { // expected-note 2{{candidate}}
>> +  struct A {
>>      constexpr A(int, float = 0); // expected-note 2{{candidate}}
>>      explicit A(int, int = 0); // expected-note 2{{candidate}}
>>      A(int, int, int = 0) = delete; // expected-note {{candidate}}
>>    };
>>
>>    struct B : A { // expected-note 2{{candidate}}
>> -    using A::A; // expected-note 7{{inherited here}}
>> +    using A::A; // expected-note 5{{inherited here}}
>>    };
>>
>>    constexpr B a(0); // expected-error {{ambiguous}}
>>
>> Modified: cfe/trunk/test/CXX/drs/dr19xx.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr19xx.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/drs/dr19xx.cpp (original)
>> +++ cfe/trunk/test/CXX/drs/dr19xx.cpp Fri Jan 13 14:46:54 2017
>> @@ -138,18 +138,21 @@ namespace dr1959 { // dr1959: 3.9
>>    struct c;
>>    struct a {
>>      a() = default;
>> -    a(const a &) = delete; // expected-note 2{{deleted}}
>> +    a(const a &) = delete; // expected-note {{deleted}}
>>      a(const b &) = delete; // not inherited
>> -    a(c &&) = delete;
>> -    template<typename T> a(T) = delete;
>> +    a(c &&) = delete; // expected-note {{not viable}}
>> +    template<typename T> a(T) = delete; // expected-note {{would take its
>> own class type by value}}
>>    };
>>
>> -  struct b : a { // expected-note {{copy constructor of 'b' is implicitly
>> deleted because base class 'dr1959::a' has a deleted copy constructor}}
>> -    using a::a;
>> +  struct b : a { // expected-note {{cannot bind}} expected-note {{deleted
>> because}}
>> +    using a::a; // expected-note 2{{inherited here}}
>>    };
>>
>>    a x;
>> -  b y = x; // expected-error {{deleted}}
>> +  // FIXME: As a resolution to an open DR against P0136R0, we disallow
>> +  // use of inherited constructors to construct from a single argument
>> +  // where the base class is reference-related to the argument type.
>> +  b y = x; // expected-error {{no viable conversion}}
>>    b z = z; // expected-error {{deleted}}
>>
>>    struct c : a {
>> @@ -158,7 +161,7 @@ namespace dr1959 { // dr1959: 3.9
>>    };
>>    // FIXME: As a resolution to an open DR against P0136R0, we disallow
>>    // use of inherited constructors to construct from a single argument
>> -  // where the derived class is reference-related to its type.
>> +  // where the base class is reference-related to the argument type.
>>    c q(static_cast<c&&>(q));
>>  #endif
>>  }
>>
>> Modified: cfe/trunk/test/CXX/special/class.inhctor/p1.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/special/class.inhctor/p1.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/special/class.inhctor/p1.cpp (original)
>> +++ cfe/trunk/test/CXX/special/class.inhctor/p1.cpp Fri Jan 13 14:46:54
>> 2017
>> @@ -3,7 +3,7 @@
>>  // Note: [class.inhctor] was removed by P0136R1. This tests the new
>> behavior
>>  // for the wording that used to be there.
>>
>> -struct A { // expected-note 8{{candidate is the implicit}}
>> +struct A { // expected-note 4{{candidate is the implicit}}
>>    A(...); // expected-note 4{{candidate constructor}} expected-note
>> 4{{candidate inherited constructor}}
>>    A(int = 0, int = 0, int = 0, int = 0, ...); // expected-note
>> 3{{candidate
>> constructor}} expected-note 3{{candidate inherited constructor}}
>>    A(int = 0, int = 0, ...); // expected-note 3{{candidate constructor}}
>> expected-note 3{{candidate inherited constructor}}
>> @@ -15,7 +15,7 @@ struct A { // expected-note 8{{candidate
>>  };
>>
>>  struct B : A { // expected-note 4{{candidate is the implicit}}
>> -  using A::A; // expected-note 19{{inherited here}}
>> +  using A::A; // expected-note 15{{inherited here}}
>>    B(void*);
>>  };
>>
>>
>> Modified: cfe/trunk/test/CXX/special/class.inhctor/p3.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/special/class.inhctor/p3.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/special/class.inhctor/p3.cpp (original)
>> +++ cfe/trunk/test/CXX/special/class.inhctor/p3.cpp Fri Jan 13 14:46:54
>> 2017
>> @@ -14,21 +14,21 @@ D1 d1a(1), d1b(1, 1);
>>
>>  D1 fd1() { return 1; }
>>
>> -struct B2 { // expected-note 2{{candidate}}
>> +struct B2 {
>>    explicit B2(int, int = 0, int = 0);
>>  };
>>  struct D2 : B2 { // expected-note 2{{candidate constructor}}
>> -  using B2::B2; // expected-note 2{{inherited here}}
>> +  using B2::B2;
>>  };
>>  D2 d2a(1), d2b(1, 1), d2c(1, 1, 1);
>>
>>  D2 fd2() { return 1; } // expected-error {{no viable conversion}}
>>
>> -struct B3 { // expected-note 2{{candidate}}
>> +struct B3 {
>>    B3(void*); // expected-note {{candidate}}
>>  };
>>  struct D3 : B3 { // expected-note 2{{candidate constructor}}
>> -  using B3::B3; // expected-note 3{{inherited here}}
>> +  using B3::B3; // expected-note {{inherited here}}
>>  };
>>  D3 fd3() { return 1; } // expected-error {{no viable conversion}}
>>
>>
>> Modified: cfe/trunk/test/CXX/special/class.inhctor/p7.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/special/class.inhctor/p7.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/special/class.inhctor/p7.cpp (original)
>> +++ cfe/trunk/test/CXX/special/class.inhctor/p7.cpp Fri Jan 13 14:46:54
>> 2017
>> @@ -3,15 +3,15 @@
>>  // Note: [class.inhctor] was removed by P0136R1. This tests the new
>> behavior
>>  // for the wording that used to be there.
>>
>> -struct B1 { // expected-note 2{{candidate}}
>> +struct B1 {
>>    B1(int); // expected-note {{candidate}}
>>  };
>> -struct B2 { // expected-note 2{{candidate}}
>> +struct B2 {
>>    B2(int); // expected-note {{candidate}}
>>  };
>>  struct D1 : B1, B2 { // expected-note 2{{candidate}}
>> -  using B1::B1; // expected-note 3{{inherited here}}
>> -  using B2::B2; // expected-note 3{{inherited here}}
>> +  using B1::B1; // expected-note {{inherited here}}
>> +  using B2::B2; // expected-note {{inherited here}}
>>  };
>>  struct D2 : B1, B2 {
>>    using B1::B1;
>>
>> Modified: cfe/trunk/test/SemaCXX/cxx11-inheriting-ctors.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/cxx11-inheriting-ctors.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/cxx11-inheriting-ctors.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/cxx11-inheriting-ctors.cpp Fri Jan 13 14:46:54
>> 2017
>> @@ -56,9 +56,9 @@ namespace InvalidConstruction {
>>  }
>>
>>  namespace ExplicitConv {
>> -  struct B {}; // expected-note 2{{candidate}}
>> +  struct B {};
>>    struct D : B { // expected-note 3{{candidate}}
>> -    using B::B; // expected-note 2{{inherited}}
>> +    using B::B;
>>    };
>>    struct X { explicit operator B(); } x;
>>    struct Y { explicit operator D(); } y;
>> @@ -68,19 +68,40 @@ namespace ExplicitConv {
>>  }
>>
>>  namespace NestedListInit {
>> -  struct B { B(); } b; // expected-note 5{{candidate}}
>> -  struct D : B { // expected-note 3{{candidate}}
>> -    using B::B; // expected-note 2{{inherited}}
>> +  struct B { B(); } b; // expected-note 3{{candidate}}
>> +  struct D : B { // expected-note 14{{not viable}}
>> +    using B::B;
>>    };
>>    // This is a bit weird. We're allowed one pair of braces for overload
>>    // resolution, and one more pair of braces due to [over.ics.list]/2.
>>    B b1 = {b};
>>    B b2 = {{b}};
>>    B b3 = {{{b}}}; // expected-error {{no match}}
>> -  // This is the same, but we get one call to D's version of B::B(const
>> B&)
>> -  // before the two permitted calls to D::D(D&&).
>> -  D d1 = {b};
>> -  D d2 = {{b}};
>> -  D d3 = {{{b}}};
>> +  // Per a proposed defect resolution, we don't get to call
>> +  // D's version of B::B(const B&) here.
>> +  D d0 = b; // expected-error {{no viable conversion}}
>> +  D d1 = {b}; // expected-error {{no match}}
>> +  D d2 = {{b}}; // expected-error {{no match}}
>> +  D d3 = {{{b}}}; // expected-error {{no match}}
>>    D d4 = {{{{b}}}}; // expected-error {{no match}}
>>  }
>> +
>> +namespace PR31606 {
>> +  // PR31606: as part of a proposed defect resolution, do not consider
>> +  // inherited constructors that would be copy constructors for any class
>> +  // between the declaring class and the constructed class (inclusive).
>> +  struct Base {};
>> +
>> +  struct A : Base {
>> +    using Base::Base;
>> +    bool operator==(A const &) const; // expected-note {{no known
>> conversion from 'PR31606::B' to 'const PR31606::A' for 1st argument}}
>> +  };
>> +
>> +  struct B : Base {
>> +    using Base::Base;
>> +  };
>> +
>> +  bool a = A{} == A{};
>> +  // Note, we do *not* allow operator=='s argument to use the inherited
>> A::A(Base&&) constructor to construct from B{}.
>> +  bool b = A{} == B{}; // expected-error {{invalid operands}}
>> +}
>>
>> Modified: cfe/trunk/test/SemaTemplate/cxx1z-using-declaration.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/cxx1z-using-declaration.cpp?rev=291955&r1=291954&r2=291955&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaTemplate/cxx1z-using-declaration.cpp (original)
>> +++ cfe/trunk/test/SemaTemplate/cxx1z-using-declaration.cpp Fri Jan 13
>> 14:46:54 2017
>> @@ -17,7 +17,7 @@ void test_Unexpanded() {
>>
>>  // Test using non-type members from pack of base classes.
>>  template<typename ...T> struct A : T... { // expected-note 2{{candidate}}
>> -  using T::T ...; // expected-note 6{{inherited here}}
>> +  using T::T ...; // expected-note 2{{inherited here}}
>>    using T::operator() ...;
>>    using T::operator T* ...;
>>    using T::h ...;
>> @@ -29,7 +29,7 @@ template<typename ...T> struct A : T...
>>  };
>>
>>  namespace test_A {
>> -  struct X { // expected-note 2{{candidate}}
>> +  struct X {
>>      X();
>>      X(int); // expected-note {{candidate}}
>>      void operator()(int); // expected-note 2{{candidate}}
>> @@ -43,7 +43,7 @@ namespace test_A {
>>      operator Y *();
>>      void h(int, int); // expected-note {{not viable}}
>>    };
>> -  struct Z { // expected-note 2{{candidate}}
>> +  struct Z {
>>      Z();
>>      Z(int); // expected-note {{candidate}}
>>      void operator()(int); // expected-note 2{{candidate}}
>>
>>
>> _______________________________________________
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>> cfe-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>
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