Implement basic support for the use of variadic templates and blocks

together. In particular: 
  - Handle the use of captured parameter pack names within blocks
  (BlockDeclRefExpr understands parameter packs now)
  - Handle the declaration and expansion of parameter packs within a block's
  parameter list, e.g., ^(Args ...args) { ... })
  - Handle instantiation of blocks where the return type was not
  explicitly specified. (unrelated, but necessary for my tests).

Together, these fixes should make blocks and variadic templates work
reasonably well together. Note that BlockDeclRefExpr is still broken
w.r.t. its computation of type and value dependence, which will still
cause problems for blocks in templates.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123849 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 37 insertions, 12 deletions

diff --git a/lib/Sema/SemaTemplateVariadic.cpp b/lib/Sema/SemaTemplateVariadic.cpp
index 38a777efb1..3f76d9f6e3 100644
--- a/lib/Sema/SemaTemplateVariadic.cpp
+++ b/lib/Sema/SemaTemplateVariadic.cpp
@@ -64,7 +64,7 @@ namespace {
       return true;
     }
 
-    /// \brief Record occurrences of (FIXME: function and) non-type template
+    /// \brief Record occurrences of function and non-type template
     /// parameter packs in an expression.
     bool VisitDeclRefExpr(DeclRefExpr *E) {
       if (E->getDecl()->isParameterPack())
@@ -73,6 +73,15 @@ namespace {
       return true;
     }
     
+    // \brief Record occurrences of function and non-type template parameter
+    // packs in a block-captured expression.
+    bool VisitBlockDeclRefExpr(BlockDeclRefExpr *E) {
+      if (E->getDecl()->isParameterPack())
+        Unexpanded.push_back(std::make_pair(E->getDecl(), E->getLocation()));
+      
+      return true;
+    }
+    
     /// \brief Record occurrences of template template parameter packs.
     bool TraverseTemplateName(TemplateName Template) {
       if (TemplateTemplateParmDecl *TTP 
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index ebc34d0f35..1cb24e70bf 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -7122,16 +7122,13 @@ TreeTransform<Derived>::TransformBlockExpr(BlockExpr *E) {
   llvm::SmallVector<QualType, 4> ParamTypes;
   
   // Parameter substitution.
-  // FIXME: Variadic templates
-  const BlockDecl *BD = E->getBlockDecl();
-  for (BlockDecl::param_const_iterator P = BD->param_begin(),
-       EN = BD->param_end(); P != EN; ++P) {
-    ParmVarDecl *OldParm = (*P);
-    ParmVarDecl *NewParm = getDerived().TransformFunctionTypeParam(OldParm,
-                                                   llvm::Optional<unsigned>());
-    Params.push_back(NewParm);
-    ParamTypes.push_back(NewParm->getType());
-  }
+  BlockDecl *BD = E->getBlockDecl();
+  if (getDerived().TransformFunctionTypeParams(E->getLocStart(), 
+                                               BD->param_begin(),
+                                               BD->param_size(), 0, ParamTypes,
+                                               &Params))
+    return true;
+  
   
   const FunctionType *BExprFunctionType = E->getFunctionType();
   QualType BExprResultType = BExprFunctionType->getResultType();
@@ -7141,6 +7138,19 @@ TreeTransform<Derived>::TransformBlockExpr(BlockExpr *E) {
     else if (BExprResultType != SemaRef.Context.DependentTy)
       CurBlock->ReturnType = getDerived().TransformType(BExprResultType);
   }
+  
+  // If the return type has not been determined yet, leave it as a dependent
+  // type; it'll get set when we process the body.
+  if (CurBlock->ReturnType.isNull())
+    CurBlock->ReturnType = getSema().Context.DependentTy;
+
+  // Don't allow returning a objc interface by value.
+  if (CurBlock->ReturnType->isObjCObjectType()) {
+    getSema().Diag(E->getLocStart(), 
+                   diag::err_object_cannot_be_passed_returned_by_value) 
+      << 0 << CurBlock->ReturnType;
+    return ExprError();
+  }
 
   QualType FunctionType = getDerived().RebuildFunctionProtoType(
                                                         CurBlock->ReturnType,
@@ -7154,7 +7164,13 @@ TreeTransform<Derived>::TransformBlockExpr(BlockExpr *E) {
   // Set the parameters on the block decl.
   if (!Params.empty())
     CurBlock->TheDecl->setParams(Params.data(), Params.size());
-    
+  
+  // If the return type wasn't explicitly set, it will have been marked as a 
+  // dependent type (DependentTy); clear out the return type setting so 
+  // we will deduce the return type when type-checking the block's body.
+  if (CurBlock->ReturnType == getSema().Context.DependentTy)
+    CurBlock->ReturnType = QualType();
+  
   // Transform the body
   StmtResult Body = getDerived().TransformStmt(E->getBody());
   if (Body.isInvalid())