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Implement C++ [over.ics.user]p3, which restricts the final conversion 

from a conversion function template specialization to one of exact
match rank. We only know how to test this in C++0x with default
function template arguments, but it's also in the C++03 spec. Fixes
PR6285.

llvm-svn: 101089
This commit is contained in:
Douglas Gregor 2010-04-12 23:42:09 +00:00
parent 5c0066f1cf
commit 2c326bce38
3 changed files with 31 additions and 1 deletions
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12
clang/lib/Sema/SemaOverload.cpp
View File

@ -2819,6 +2819,17 @@ Sema::AddConversionCandidate(CXXConversionDecl *Conversion,
switch (ICS.getKind()) {
case ImplicitConversionSequence::StandardConversion:
Candidate.FinalConversion = ICS.Standard;
// C++ [over.ics.user]p3:
// If the user-defined conversion is specified by a specialization of a
// conversion function template, the second standard conversion sequence
// shall have exact match rank.
if (Conversion->getPrimaryTemplate() &&
GetConversionRank(ICS.Standard.Second) != ICR_Exact_Match) {
Candidate.Viable = false;
Candidate.FailureKind = ovl_fail_final_conversion_not_exact;
}
break;
case ImplicitConversionSequence::BadConversion:
@ -4628,6 +4639,7 @@ void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
case ovl_fail_trivial_conversion:
case ovl_fail_bad_final_conversion:
case ovl_fail_final_conversion_not_exact:
return S.NoteOverloadCandidate(Fn);
case ovl_fail_bad_conversion: {

6
clang/lib/Sema/SemaOverload.h
View File

@ -440,7 +440,11 @@ namespace clang {
/// This conversion candidate is not viable because its result
/// type is not implicitly convertible to the desired type.
ovl_fail_bad_final_conversion
ovl_fail_bad_final_conversion,
/// This conversion function template specialization candidate is not
/// viable because the final conversion was not an exact match.
ovl_fail_final_conversion_not_exact
};
/// OverloadCandidate - A single candidate in an overload set (C++ 13.3).

14
clang/test/CXX/over/over.match/over.match.best/over.best.ics/over.ics.user/p3-0x.cpp Normal file
View File

@ -0,0 +1,14 @@
// RUN: %clang_cc1 -fsyntax-only -std=c++0x -verify %s
namespace PR6285 {
template<typename T> struct identity
{ typedef T type; };
struct D {
template<typename T = short>
operator typename identity<T>::type(); // expected-note{{candidate}}
};
int f() { return D(); } // expected-error{{no viable conversion}}
}