Implement support for default template arguments of function templates.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89874 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 41 insertions, 15 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index c5571d1643..06b2dec590 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -1272,18 +1272,56 @@ Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
   TemplateParameterList *TemplateParams
     = FunctionTemplate->getTemplateParameters();
 
+  // Template argument deduction for function templates in a SFINAE context.
+  // Trap any errors that might occur.
+  SFINAETrap Trap(*this);
+
+  // Enter a new template instantiation context while we instantiate the
+  // actual function declaration.
+  InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
+                             FunctionTemplate, Deduced.data(), Deduced.size(),
+              ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution);
+  if (Inst)
+    return TDK_InstantiationDepth;
+
   // C++ [temp.deduct.type]p2:
   //   [...] or if any template argument remains neither deduced nor
   //   explicitly specified, template argument deduction fails.
   TemplateArgumentListBuilder Builder(TemplateParams, Deduced.size());
   for (unsigned I = 0, N = Deduced.size(); I != N; ++I) {
-    if (Deduced[I].isNull()) {
+    if (!Deduced[I].isNull()) {
+      Builder.Append(Deduced[I]);
+      continue;
+    }
+
+    // Substitute into the default template argument, if available. 
+    NamedDecl *Param = FunctionTemplate->getTemplateParameters()->getParam(I);
+    TemplateArgumentLoc DefArg
+      = SubstDefaultTemplateArgumentIfAvailable(FunctionTemplate,
+                                              FunctionTemplate->getLocation(),
+                                  FunctionTemplate->getSourceRange().getEnd(),
+                                                Param,
+                                                Builder);
+
+    // If there was no default argument, deduction is incomplete.
+    if (DefArg.getArgument().isNull()) {
       Info.Param = makeTemplateParameter(
-                            const_cast<NamedDecl *>(TemplateParams->getParam(I)));
+                         const_cast<NamedDecl *>(TemplateParams->getParam(I)));
       return TDK_Incomplete;
     }
+    
+    // Check whether we can actually use the default argument.
+    if (CheckTemplateArgument(Param, DefArg,
+                              FunctionTemplate,
+                              FunctionTemplate->getLocation(),
+                              FunctionTemplate->getSourceRange().getEnd(),
+                              Builder)) {
+      Info.Param = makeTemplateParameter(
+                         const_cast<NamedDecl *>(TemplateParams->getParam(I)));
+      return TDK_SubstitutionFailure;
+    }
 
-    Builder.Append(Deduced[I]);
+    // If we get here, we successfully used the default template argument.
   }
 
   // Form the template argument list from the deduced template arguments.
@@ -1291,18 +1329,6 @@ Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
     = new (Context) TemplateArgumentList(Context, Builder, /*TakeArgs=*/true);
   Info.reset(DeducedArgumentList);
 
-  // Template argument deduction for function templates in a SFINAE context.
-  // Trap any errors that might occur.
-  SFINAETrap Trap(*this);
-
-  // Enter a new template instantiation context while we instantiate the
-  // actual function declaration.
-  InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
-                             FunctionTemplate, Deduced.data(), Deduced.size(),
-              ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution);
-  if (Inst)
-    return TDK_InstantiationDepth;
-
   // Substitute the deduced template arguments into the function template
   // declaration to produce the function template specialization.
   Specialization = cast_or_null<FunctionDecl>(