Unverified Commit e6d0b126 authored by Utkarsh Saxena's avatar Utkarsh Saxena Committed by GitHub
Browse files

Correctly compute conversion seq for args to fn with reversed param order (#68999) 

We associated conversion seq for args (when reversed) to the wrong
index.
This lead to clang believing reversed `operator==` a worse overload
candidate than the `operator==` without reversed args when both these
candidate were ambiguous.

Fixes https://github.com/llvm/llvm-project/issues/53954
parent 31512811

clang/docs/ReleaseNotes.rst

+2 −0
Original line number Diff line number Diff line
@@ -117,6 +117,8 @@ C++ Language Changes 


C++20 Feature Support

^^^^^^^^^^^^^^^^^^^^^

- Fix a bug in conversion sequence of arguments to a function with reversed parameter order.

  Fixes `GH <https://github.com/llvm/llvm-project/issues/53954>`_.



C++23 Feature Support

^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaOverload.cpp

+1 −1
Original line number Diff line number Diff line
@@ -7688,7 +7688,7 @@ bool Sema::CheckNonDependentConversions( 
    QualType ParamType = ParamTypes[I + Offset];

    if (!ParamType->isDependentType()) {

      unsigned ConvIdx = PO == OverloadCandidateParamOrder::Reversed

                             ? 0

                             ? Args.size() - 1 - (ThisConversions + I)

                             : (ThisConversions + I);

      Conversions[ConvIdx]

        = TryCopyInitialization(*this, Args[I], ParamType,

clang/test/CXX/over/over.match/over.match.funcs/over.match.oper/p3-2a.cpp

+35 −0
Original line number Diff line number Diff line
@@ -324,6 +324,41 @@ bool x = X() == X(); // expected-warning {{ambiguous}} 
}

} // namespace P2468R2



namespace GH53954{

namespace test1 {

struct P {

    template <class T>

    friend bool operator==(const P&, const T&); // expected-note {{candidate}} \

                                                  // expected-note {{reversed parameter order}}

};

struct A : public P {};

struct B : public P {};

bool check(A a, B b) { return a == b; } // expected-error {{ '==' is ambiguous}}

}



namespace test2 {

struct P {

    template <class T>

    friend bool operator==(const T&, const P&); // expected-note {{candidate}} \

                                                // expected-note {{reversed parameter order}}

};

struct A : public P {};

struct B : public P {};

bool check(A a, B b) { return a == b; } // expected-error {{ '==' is ambiguous}}

}



namespace test3 {

struct P {

  template<class S>

  bool operator==(const S &) const; // expected-note {{candidate}} \

                                    // expected-note {{reversed parameter order}}

};

struct A : public P {};

struct B : public P {};

bool check(A a, B b) { return a == b; } // expected-error {{ '==' is ambiguous}}

}

}



#else // NO_ERRORS



namespace problem_cases {