ychen created this revision.
ychen added reviewers: rsmith, aaron.ballman.
Herald added a project: All.
ychen requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D128745
Files:
clang/lib/Sema/SemaTemplateDeduction.cpp
clang/test/CXX/drs/dr6xx.cpp
Index: clang/test/CXX/drs/dr6xx.cpp
===================================================================
--- clang/test/CXX/drs/dr6xx.cpp
+++ clang/test/CXX/drs/dr6xx.cpp
@@ -1086,15 +1086,12 @@
template <typename T, typename U> struct A {};
template <typename T, typename U> void f(U, A<U, T> *p = 0); //
expected-note {{candidate}}
template <typename U> int &f(U, A<U, U> *p = 0); // expected-note
{{candidate}}
- template <typename T> void g(T, T = T());
- template <typename T, typename... U> void g(T, U...); // expected-error
0-1{{C++11}}
+ template <typename T> void g(T, T = T()); // expected-note {{candidate}}
+ template <typename T, typename... U> void g(T, U...); // expected-note
{{candidate}} // expected-error 0-1{{C++11}}
void h() {
int &r = f<int>(42, (A<int, int> *)0);
f<int>(42); // expected-error {{ambiguous}}
- // FIXME: We should reject this due to ambiguity between the pack and the
- // default argument. Only parameters with arguments are considered during
- // partial ordering of function templates.
- g(42);
+ g(42); // expected-error {{ambiguous}}
}
}
Index: clang/lib/Sema/SemaTemplateDeduction.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateDeduction.cpp
+++ clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5181,13 +5181,21 @@
if (!Better1 && !Better2) // Neither is better than the other
return JudgeByConstraints();
- // FIXME: This mimics what GCC implements, but doesn't match up with the
- // proposed resolution for core issue 692. This area needs to be sorted out,
- // but for now we attempt to maintain compatibility.
+ const unsigned NumParams1 = FT1->getTemplatedDecl()->getNumParams();
+ const unsigned NumParams2 = FT2->getTemplatedDecl()->getNumParams();
+
+ // C++ [temp.deduct.partial]p11:
+ // ... and if G has a trailing function parameter pack for which F does not
+ // have a corresponding parameter, and if F does not have a trailing
+ // function parameter pack, then F is more specialized than G.
bool Variadic1 = isVariadicFunctionTemplate(FT1);
bool Variadic2 = isVariadicFunctionTemplate(FT2);
- if (Variadic1 != Variadic2)
- return Variadic1? FT2 : FT1;
+ if (Variadic1 != Variadic2) {
+ if (Variadic1 && NumParams1 > NumParams2)
+ return FT2;
+ if (Variadic2 && NumParams2 > NumParams1)
+ return FT1;
+ }
return JudgeByConstraints();
}
Index: clang/test/CXX/drs/dr6xx.cpp
===================================================================
--- clang/test/CXX/drs/dr6xx.cpp
+++ clang/test/CXX/drs/dr6xx.cpp
@@ -1086,15 +1086,12 @@
template <typename T, typename U> struct A {};
template <typename T, typename U> void f(U, A<U, T> *p = 0); // expected-note {{candidate}}
template <typename U> int &f(U, A<U, U> *p = 0); // expected-note {{candidate}}
- template <typename T> void g(T, T = T());
- template <typename T, typename... U> void g(T, U...); // expected-error 0-1{{C++11}}
+ template <typename T> void g(T, T = T()); // expected-note {{candidate}}
+ template <typename T, typename... U> void g(T, U...); // expected-note {{candidate}} // expected-error 0-1{{C++11}}
void h() {
int &r = f<int>(42, (A<int, int> *)0);
f<int>(42); // expected-error {{ambiguous}}
- // FIXME: We should reject this due to ambiguity between the pack and the
- // default argument. Only parameters with arguments are considered during
- // partial ordering of function templates.
- g(42);
+ g(42); // expected-error {{ambiguous}}
}
}
Index: clang/lib/Sema/SemaTemplateDeduction.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateDeduction.cpp
+++ clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5181,13 +5181,21 @@
if (!Better1 && !Better2) // Neither is better than the other
return JudgeByConstraints();
- // FIXME: This mimics what GCC implements, but doesn't match up with the
- // proposed resolution for core issue 692. This area needs to be sorted out,
- // but for now we attempt to maintain compatibility.
+ const unsigned NumParams1 = FT1->getTemplatedDecl()->getNumParams();
+ const unsigned NumParams2 = FT2->getTemplatedDecl()->getNumParams();
+
+ // C++ [temp.deduct.partial]p11:
+ // ... and if G has a trailing function parameter pack for which F does not
+ // have a corresponding parameter, and if F does not have a trailing
+ // function parameter pack, then F is more specialized than G.
bool Variadic1 = isVariadicFunctionTemplate(FT1);
bool Variadic2 = isVariadicFunctionTemplate(FT2);
- if (Variadic1 != Variadic2)
- return Variadic1? FT2 : FT1;
+ if (Variadic1 != Variadic2) {
+ if (Variadic1 && NumParams1 > NumParams2)
+ return FT2;
+ if (Variadic2 && NumParams2 > NumParams1)
+ return FT1;
+ }
return JudgeByConstraints();
}
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