Implement partial ordering of class template partial specializations

and function templates that contain variadic templates. This involves
three small-ish changes:

  (1) When transforming a pack expansion, if the transformed argument
  still contains unexpanded parameter packs, build a pack
  expansion. This can happen during the substitution that occurs into
  class template partial specialiation template arguments during
  partial ordering. 
 
  (2) When performing template argument deduction where the argument
  is a pack expansion, match against the pattern of that pack
  expansion.

  (3) When performing template argument deduction against a non-pack
  parameter, or a non-expansion template argument, deduction fails if
  the argument itself is a pack expansion (C++0x
  [temp.deduct.type]p22).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123279 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 114 insertions, 6 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 6d0db4a541..dcc1ada3e8 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -80,7 +80,7 @@ static Sema::TemplateDeductionResult
 DeduceTemplateArguments(Sema &S,
                         TemplateParameterList *TemplateParams,
                         const TemplateArgument &Param,
-                        const TemplateArgument &Arg,
+                        TemplateArgument Arg,
                         TemplateDeductionInfo &Info,
                       llvm::SmallVectorImpl<DeducedTemplateArgument> &Deduced);
 
@@ -677,6 +677,13 @@ DeduceTemplateArguments(Sema &S,
       if (ArgIdx >= NumArgs)
         return Sema::TDK_NonDeducedMismatch;
           
+      if (isa<PackExpansionType>(Args[ArgIdx])) {
+        // C++0x [temp.deduct.type]p22:
+        //   If the original function parameter associated with A is a function
+        //   parameter pack and the function parameter associated with P is not
+        //   a function parameter pack, then template argument deduction fails.
+        return Sema::TDK_NonDeducedMismatch;
+      }
       
       if (Sema::TemplateDeductionResult Result
             = DeduceTemplateArguments(S, TemplateParams,
@@ -814,6 +821,12 @@ DeduceTemplateArguments(Sema &S,
   QualType Param = S.Context.getCanonicalType(ParamIn);
   QualType Arg = S.Context.getCanonicalType(ArgIn);
 
+  // If the argument type is a pack expansion, look at its pattern.
+  // This isn't explicitly called out 
+  if (const PackExpansionType *ArgExpansion
+                                            = dyn_cast<PackExpansionType>(Arg))
+    Arg = ArgExpansion->getPattern();
+      
   if (PartialOrdering) {
     // C++0x [temp.deduct.partial]p5:
     //   Before the partial ordering is done, certain transformations are 
@@ -1273,9 +1286,15 @@ static Sema::TemplateDeductionResult
 DeduceTemplateArguments(Sema &S,
                         TemplateParameterList *TemplateParams,
                         const TemplateArgument &Param,
-                        const TemplateArgument &Arg,
+                        TemplateArgument Arg,
                         TemplateDeductionInfo &Info,
                     llvm::SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  // If the template argument is a pack expansion, perform template argument
+  // deduction against the pattern of that expansion. This only occurs during
+  // partial ordering.
+  if (Arg.isPackExpansion())
+    Arg = Arg.getPackExpansionPattern();
+  
   switch (Param.getKind()) {
   case TemplateArgument::Null:
     assert(false && "Null template argument in parameter list");
@@ -1448,11 +1467,17 @@ DeduceTemplateArguments(Sema &S,
         return NumberOfArgumentsMustMatch? Sema::TDK_NonDeducedMismatch
                                          : Sema::TDK_Success;
       
+      if (Args[ArgIdx].isPackExpansion()) {
+        // FIXME: We follow the logic of C++0x [temp.deduct.type]p22 here,
+        // but applied to pack expansions that are template arguments.
+        return Sema::TDK_NonDeducedMismatch;
+      }
+      
       // Perform deduction for this Pi/Ai pair.
       if (Sema::TemplateDeductionResult Result
-          = DeduceTemplateArguments(S, TemplateParams,
-                                    Params[ParamIdx], Args[ArgIdx],
-                                    Info, Deduced))
+            = DeduceTemplateArguments(S, TemplateParams,
+                                      Params[ParamIdx], Args[ArgIdx],
+                                      Info, Deduced))
         return Result;  
       
       // Move to the next argument.
@@ -1792,7 +1817,7 @@ FinishTemplateArgumentDeduction(Sema &S,
       return Sema::TDK_SubstitutionFailure;
     }
   }
-  
+    
   // Form the template argument list from the deduced template arguments.
   TemplateArgumentList *DeducedArgumentList
     = TemplateArgumentList::CreateCopy(S.Context, Builder.data(), 
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index bc1ac1e6ae..e63cc7da7c 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -2327,6 +2327,12 @@ bool TreeTransform<Derived>::TransformExprs(Expr **Inputs,
         if (Out.isInvalid())
           return true;
 
+        if (Out.get()->containsUnexpandedParameterPack()) {
+          Out = RebuildPackExpansion(Out.get(), Expansion->getEllipsisLoc());
+          if (Out.isInvalid())
+            return true;
+        }
+        
         if (ArgChanged)
           *ArgChanged = true;  
         Outputs.push_back(Out.get());
@@ -2847,6 +2853,12 @@ bool TreeTransform<Derived>::TransformTemplateArguments(InputIterator First,
         if (getDerived().TransformTemplateArgument(Pattern, Out))
           return true;
         
+        if (Out.getArgument().containsUnexpandedParameterPack()) {
+          Out = getDerived().RebuildPackExpansion(Out, Ellipsis);
+          if (Out.getArgument().isNull())
+            return true;
+        }
+          
         Outputs.addArgument(Out);
       }
       
diff --git a/test/CXX/temp/temp.decls/temp.variadic/partial-ordering.cpp b/test/CXX/temp/temp.decls/temp.variadic/partial-ordering.cpp
new file mode 100644
index 0000000000..2e85c18fff
--- /dev/null
+++ b/test/CXX/temp/temp.decls/temp.variadic/partial-ordering.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -std=c++0x -fsyntax-only -verify %s
+
+// Various tests related to partial ordering of variadic templates.
+template<typename ...Types> struct tuple;
+
+template<typename Tuple> 
+struct X1 {
+  static const unsigned value = 0;
+};
+
+template<typename Head, typename ...Tail>
+struct X1<tuple<Head, Tail...> > {
+  static const unsigned value = 1;
+};
+
+template<typename Head, typename ...Tail>
+struct X1<tuple<Head, Tail&...> > {
+  static const unsigned value = 2;
+};
+
+template<typename Head, typename ...Tail>
+struct X1<tuple<Head&, Tail&...> > {
+  static const unsigned value = 3;
+};
+
+int check0[X1<tuple<>>::value == 0? 1 : -1];
+int check1[X1<tuple<int>>::value == 2? 1 : -1];
+int check2[X1<tuple<int, int>>::value == 1? 1 : -1];
+int check3[X1<tuple<int, int&>>::value == 2? 1 : -1];
+int check4[X1<tuple<int&, int&>>::value == 3? 1 : -1];
diff --git a/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp b/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp
new file mode 100644
index 0000000000..116810082d
--- /dev/null
+++ b/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -std=c++0x -fsyntax-only -verify %s
+
+// Note: Partial ordering of function templates containing template
+// parameter packs is independent of the number of deduced arguments
+// for those template parameter packs.
+template<class ...> struct Tuple { }; 
+template<class ... Types> int &g(Tuple<Types ...>); // #1 
+template<class T1, class ... Types> float &g(Tuple<T1, Types ...>); // #2
+template<class T1, class ... Types> double &g(Tuple<T1, Types& ...>); // #3
+
+void test_g() {
+  int &ir1 = g(Tuple<>()); 
+  float &fr1 = g(Tuple<int, float>()); 
+  double &dr1 = g(Tuple<int, float&>()); 
+  double &dr2 = g(Tuple<int>());
+}
+
+template<class ... Types> int &h(int (*)(Types ...)); // #1 
+template<class T1, class ... Types> float &h(int (*)(T1, Types ...)); // #2
+template<class T1, class ... Types> double &h(int (*)(T1, Types& ...)); // #3
+
+void test_h() {
+  int &ir1 = h((int(*)())0); 
+  float &fr1 = h((int(*)(int, float))0);
+  double &dr1 = h((int(*)(int, float&))0);
+  double &dr2 = h((int(*)(int))0);
+}
diff --git a/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.type/p22.cpp b/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.type/p22.cpp
new file mode 100644
index 0000000000..4326a691cb
--- /dev/null
+++ b/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.type/p22.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -std=c++0x -fsyntax-only -verify %s
+
+// If the original function parameter associated with A is a function
+// parameter pack and the function parameter associated with P is not
+// a function parameter pack, then template argument deduction fails.
+template<class ... Args> int& f(Args ... args); 
+template<class T1, class ... Args> float& f(T1 a1, Args ... args); 
+template<class T1, class T2> double& f(T1 a1, T2 a2);
+
+void test_f() {
+  int &ir1 = f();
+  float &fr1 = f(1, 2, 3);
+  double &dr1 = f(1, 2);
+}