Implement support for non-type template parameter packs whose type is

a pack expansion, e.g., the parameter pack Values in:

  template<typename ...Types>
  struct Outer {
    template<Types ...Values>
    struct Inner;
  };

This new implementation approach introduces the notion of an
"expanded" non-type template parameter pack, for which we have already
expanded the types of the parameter pack (to, say, "int*, float*",
for Outer<int*, float*>) but have not yet expanded the values. Aside
from creating these expanded non-type template parameter packs, this
patch updates template argument checking and non-type template
parameter pack instantiation to make use of the appropriate types in
the parameter pack.

llvm-svn: 123845

2 files changed, 42 insertions, 14 deletions

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 5c66a9680f9..757433228fd 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1155,13 +1155,21 @@ void ASTDeclReader::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
   // TemplateParmPosition.
   D->setDepth(Record[Idx++]);
   D->setPosition(Record[Idx++]);
-  // Rest of NonTypeTemplateParmDecl.
-  D->ParameterPack = Record[Idx++];
-  if (Record[Idx++]) {
-    Expr *DefArg = Reader.ReadExpr(F);
-    bool Inherited = Record[Idx++];
-    D->setDefaultArgument(DefArg, Inherited);
- }
+  if (D->isExpandedParameterPack()) {
+    void **Data = reinterpret_cast<void **>(D + 1);
+    for (unsigned I = 0, N = D->getNumExpansionTypes(); I != N; ++I) {
+      Data[2*I] = Reader.GetType(Record[Idx++]).getAsOpaquePtr();
+      Data[2*I + 1] = GetTypeSourceInfo(Record, Idx);
+    }
+  } else {
+    // Rest of NonTypeTemplateParmDecl.
+    D->ParameterPack = Record[Idx++];
+    if (Record[Idx++]) {
+      Expr *DefArg = Reader.ReadExpr(F);
+      bool Inherited = Record[Idx++];
+      D->setDefaultArgument(DefArg, Inherited);
+   }
+  }
 }
 
 void ASTDeclReader::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
@@ -1433,6 +1441,11 @@ Decl *ASTReader::ReadDeclRecord(unsigned Index, DeclID ID) {
     D = NonTypeTemplateParmDecl::Create(*Context, 0, SourceLocation(), 0,0,0,
                                         QualType(), false, 0);
     break;
+  case DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK:
+    D = NonTypeTemplateParmDecl::Create(*Context, 0, SourceLocation(), 0, 0,
+                                        0, QualType(), 0, 0, Record[Idx++],
+                                        0);
+    break;
   case DECL_TEMPLATE_TEMPLATE_PARM:
     D = TemplateTemplateParmDecl::Create(*Context, 0, SourceLocation(), 0, 0,
                                          false, 0, 0);
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index c329711ecff..507c66931c5 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -988,18 +988,33 @@ void ASTDeclWriter::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
 }
 
 void ASTDeclWriter::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
+  // For an expanded parameter pack, record the number of expansion types here
+  // so that it's easier for 
+  if (D->isExpandedParameterPack())
+    Record.push_back(D->getNumExpansionTypes());
+  
   VisitVarDecl(D);
   // TemplateParmPosition.
   Record.push_back(D->getDepth());
   Record.push_back(D->getPosition());
-  // Rest of NonTypeTemplateParmDecl.
-  Record.push_back(D->isParameterPack());
-  Record.push_back(D->getDefaultArgument() != 0);
-  if (D->getDefaultArgument()) {
-    Writer.AddStmt(D->getDefaultArgument());
-    Record.push_back(D->defaultArgumentWasInherited());
+  
+  if (D->isExpandedParameterPack()) {
+    for (unsigned I = 0, N = D->getNumExpansionTypes(); I != N; ++I) {
+      Writer.AddTypeRef(D->getExpansionType(I), Record);
+      Writer.AddTypeSourceInfo(D->getExpansionTypeSourceInfo(I), Record);
+    }
+      
+    Code = serialization::DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK;
+  } else {
+    // Rest of NonTypeTemplateParmDecl.
+    Record.push_back(D->isParameterPack());
+    Record.push_back(D->getDefaultArgument() != 0);
+    if (D->getDefaultArgument()) {
+      Writer.AddStmt(D->getDefaultArgument());
+      Record.push_back(D->defaultArgumentWasInherited());
+    }
+    Code = serialization::DECL_NON_TYPE_TEMPLATE_PARM;
   }
-  Code = serialization::DECL_NON_TYPE_TEMPLATE_PARM;
 }
 
 void ASTDeclWriter::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {