Implement template argument deduction from a call to a function

template whose last parameter is a parameter pack. This allows us to
form a call to, e.g.,

  template<typename ...Args1, typename ...Args2>
  void f(std::pair<Args1, Args2> ...pairs);

given zero or more instances of "pair".

llvm-svn: 122973

1 files changed, 13 insertions, 4 deletions

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index c51d2cdc37c..a76a5748b46 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1442,11 +1442,20 @@ void FunctionDecl::setParams(ASTContext &C,
 /// getMinRequiredArguments - Returns the minimum number of arguments
 /// needed to call this function. This may be fewer than the number of
 /// function parameters, if some of the parameters have default
-/// arguments (in C++).
+/// arguments (in C++) or the last parameter is a parameter pack.
 unsigned FunctionDecl::getMinRequiredArguments() const {
-  unsigned NumRequiredArgs = getNumParams();
-  while (NumRequiredArgs > 0
-         && getParamDecl(NumRequiredArgs-1)->hasDefaultArg())
+  unsigned NumRequiredArgs = getNumParams();  
+  
+  // If the last parameter is a parameter pack, we don't need an argument for 
+  // it.
+  if (NumRequiredArgs > 0 &&
+      getParamDecl(NumRequiredArgs - 1)->isParameterPack())
+    --NumRequiredArgs;
+      
+  // If this parameter has a default argument, we don't need an argument for
+  // it.
+  while (NumRequiredArgs > 0 &&
+         getParamDecl(NumRequiredArgs-1)->hasDefaultArg())
     --NumRequiredArgs;
 
   return NumRequiredArgs;