PR17075: When performing partial ordering of a member function against a

non-member function, the number of arguments in the two candidate calls
will be different (the non-member call will have one extra argument).
We used to get confused by this, and fail to compare the last argument
when testing whether the member is better, resulting in us always
thinking it is, even if the non-member is more specialized in the last
argument.

llvm-svn: 190470

2 files changed, 45 insertions, 41 deletions

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index ea4fe10eac1..c7620e49f7c 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -7962,7 +7962,8 @@ isBetterOverloadCandidate(Sema &S,
                                          Loc,
                        isa<CXXConversionDecl>(Cand1.Function)? TPOC_Conversion
                                                              : TPOC_Call,
-                                         Cand1.ExplicitCallArguments))
+                                         Cand1.ExplicitCallArguments,
+                                         Cand2.ExplicitCallArguments))
       return BetterTemplate == Cand1.Function->getPrimaryTemplate();
   }
 
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 30788c45696..bc4f3ad83a3 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3979,7 +3979,7 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
                                      FunctionTemplateDecl *FT1,
                                      FunctionTemplateDecl *FT2,
                                      TemplatePartialOrderingContext TPOC,
-                                     unsigned NumCallArguments,
+                                     unsigned NumCallArguments1,
     SmallVectorImpl<RefParamPartialOrderingComparison> *RefParamComparisons) {
   FunctionDecl *FD1 = FT1->getTemplatedDecl();
   FunctionDecl *FD2 = FT2->getTemplatedDecl();
@@ -3995,19 +3995,13 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
   //   The types used to determine the ordering depend on the context in which
   //   the partial ordering is done:
   TemplateDeductionInfo Info(Loc);
-  CXXMethodDecl *Method1 = 0;
-  CXXMethodDecl *Method2 = 0;
-  bool IsNonStatic2 = false;
-  bool IsNonStatic1 = false;
-  unsigned Skip2 = 0;
+  SmallVector<QualType, 4> Args2;
   switch (TPOC) {
   case TPOC_Call: {
     //   - In the context of a function call, the function parameter types are
     //     used.
-    Method1 = dyn_cast<CXXMethodDecl>(FD1);
-    Method2 = dyn_cast<CXXMethodDecl>(FD2);
-    IsNonStatic1 = Method1 && !Method1->isStatic();
-    IsNonStatic2 = Method2 && !Method2->isStatic();
+    CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
+    CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
 
     // C++11 [temp.func.order]p3:
     //   [...] If only one of the function templates is a non-static
@@ -4026,26 +4020,39 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
     // first argument of the free function, which seems to match
     // existing practice.
     SmallVector<QualType, 4> Args1;
-    unsigned Skip1 = !S.getLangOpts().CPlusPlus11 && IsNonStatic2 && !Method1;
-    if (S.getLangOpts().CPlusPlus11 && IsNonStatic1 && !Method2)
-      AddImplicitObjectParameterType(S.Context, Method1, Args1);
+
+    unsigned Skip1 = 0, Skip2 = 0;
+    unsigned NumComparedArguments = NumCallArguments1;
+
+    if (!Method2 && Method1 && !Method1->isStatic()) {
+      if (S.getLangOpts().CPlusPlus11) {
+        // Compare 'this' from Method1 against first parameter from Method2.
+        AddImplicitObjectParameterType(S.Context, Method1, Args1);
+        ++NumComparedArguments;
+      } else
+        // Ignore first parameter from Method2.
+        ++Skip2;
+    } else if (!Method1 && Method2 && !Method2->isStatic()) {
+      if (S.getLangOpts().CPlusPlus11)
+        // Compare 'this' from Method2 against first parameter from Method1.
+        AddImplicitObjectParameterType(S.Context, Method2, Args2);
+      else
+        // Ignore first parameter from Method1.
+        ++Skip1;
+    }
+
     Args1.insert(Args1.end(),
                  Proto1->arg_type_begin() + Skip1, Proto1->arg_type_end());
-
-    SmallVector<QualType, 4> Args2;
-    Skip2 = !S.getLangOpts().CPlusPlus11 && IsNonStatic1 && !Method2;
-    if (S.getLangOpts().CPlusPlus11 && IsNonStatic2 && !Method1)
-      AddImplicitObjectParameterType(S.Context, Method2, Args2);
     Args2.insert(Args2.end(),
                  Proto2->arg_type_begin() + Skip2, Proto2->arg_type_end());
 
     // C++ [temp.func.order]p5:
     //   The presence of unused ellipsis and default arguments has no effect on
     //   the partial ordering of function templates.
-    if (Args1.size() > NumCallArguments)
-      Args1.resize(NumCallArguments);
-    if (Args2.size() > NumCallArguments)
-      Args2.resize(NumCallArguments);
+    if (Args1.size() > NumComparedArguments)
+      Args1.resize(NumComparedArguments);
+    if (Args2.size() > NumComparedArguments)
+      Args2.resize(NumComparedArguments);
     if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
                                 Args1.data(), Args1.size(), Info, Deduced,
                                 TDF_None, /*PartialOrdering=*/true,
@@ -4099,20 +4106,12 @@ static bool isAtLeastAsSpecializedAs(Sema &S,
   // Figure out which template parameters were used.
   llvm::SmallBitVector UsedParameters(TemplateParams->size());
   switch (TPOC) {
-  case TPOC_Call: {
-    unsigned NumParams = std::min(NumCallArguments,
-                                  std::min(Proto1->getNumArgs(),
-                                           Proto2->getNumArgs()));
-    if (S.getLangOpts().CPlusPlus11 && IsNonStatic2 && !IsNonStatic1)
-      ::MarkUsedTemplateParameters(S.Context, Method2->getThisType(S.Context),
-                                   false,
-                                   TemplateParams->getDepth(), UsedParameters);
-    for (unsigned I = Skip2; I < NumParams; ++I)
-      ::MarkUsedTemplateParameters(S.Context, Proto2->getArgType(I), false,
+  case TPOC_Call:
+    for (unsigned I = 0, N = Args2.size(); I != N; ++I)
+      ::MarkUsedTemplateParameters(S.Context, Args2[I], false,
                                    TemplateParams->getDepth(),
                                    UsedParameters);
     break;
-  }
 
   case TPOC_Conversion:
     ::MarkUsedTemplateParameters(S.Context, Proto2->getResultType(), false,
@@ -4167,8 +4166,11 @@ static bool isVariadicFunctionTemplate(FunctionTemplateDecl *FunTmpl) {
 /// \param TPOC the context in which we are performing partial ordering of
 /// function templates.
 ///
-/// \param NumCallArguments The number of arguments in a call, used only
-/// when \c TPOC is \c TPOC_Call.
+/// \param NumCallArguments1 The number of arguments in the call to FT1, used
+/// only when \c TPOC is \c TPOC_Call.
+///
+/// \param NumCallArguments2 The number of arguments in the call to FT2, used
+/// only when \c TPOC is \c TPOC_Call.
 ///
 /// \returns the more specialized function template. If neither
 /// template is more specialized, returns NULL.
@@ -4177,12 +4179,13 @@ Sema::getMoreSpecializedTemplate(FunctionTemplateDecl *FT1,
                                  FunctionTemplateDecl *FT2,
                                  SourceLocation Loc,
                                  TemplatePartialOrderingContext TPOC,
-                                 unsigned NumCallArguments) {
+                                 unsigned NumCallArguments1,
+                                 unsigned NumCallArguments2) {
   SmallVector<RefParamPartialOrderingComparison, 4> RefParamComparisons;
   bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
-                                          NumCallArguments, 0);
+                                          NumCallArguments1, 0);
   bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
-                                          NumCallArguments,
+                                          NumCallArguments2,
                                           &RefParamComparisons);
 
   if (Better1 != Better2) // We have a clear winner
@@ -4336,7 +4339,7 @@ UnresolvedSetIterator Sema::getMostSpecialized(
       = cast<FunctionDecl>(*I)->getPrimaryTemplate();
     assert(Challenger && "Not a function template specialization?");
     if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
-                                                  Loc, TPOC_Other, 0),
+                                                  Loc, TPOC_Other, 0, 0),
                        Challenger)) {
       Best = I;
       BestTemplate = Challenger;
@@ -4351,7 +4354,7 @@ UnresolvedSetIterator Sema::getMostSpecialized(
       = cast<FunctionDecl>(*I)->getPrimaryTemplate();
     if (I != Best &&
         !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
-                                                   Loc, TPOC_Other, 0),
+                                                   Loc, TPOC_Other, 0, 0),
                         BestTemplate)) {
       Ambiguous = true;
       break;