[AST] Use llvm::TrailingObjects in CXXTryStmt

[bricci]

Summary

1. Use llvm::TrailingObjects in CXXTryStmt instead of manually doing the reinterpret_casts + pointer arithmetic. This is more consistent with other classes using this idiom and this make it clearer that this class has trailing objects.
2. Make the class CXXTryStmt final since it has trailing objects.
3. Move the friend declarations together.

No functional changes.

[bricci]

1. Remove unnecessary use of getTrailingObjects and use getStmts instead.
2. Move friend class ASTStmtReader; to the top with the other friend declaration.
3. Reword message.

[bricci]

wrong diff

[bkramer]

lg

include/clang/AST/StmtCXX.h

public:
 
   child_range children() { return child_range(&HandlerBlock, &HandlerBlock+1); }
 
   friend class ASTStmtReader;
 };
 
 /// CXXTryStmt - A C++ try block, including all handlers.
 ///
-class CXXTryStmt : public Stmt {
+class CXXTryStmt final : public Stmt,
+                         private llvm::TrailingObjects<CXXTryStmt, Stmt *> {
+
+  friend TrailingObjects;
+  friend class ASTStmtReader;
+
   SourceLocation TryLoc;
   unsigned NumHandlers;
+  size_t numTrailingObjects(OverloadToken<Stmt *>) const { return NumHandlers; }
 
   CXXTryStmt(SourceLocation tryLoc, Stmt *tryBlock, ArrayRef<Stmt*> handlers);
-
   CXXTryStmt(EmptyShell Empty, unsigned numHandlers)
     : Stmt(CXXTryStmtClass), NumHandlers(numHandlers) { }
 
-  Stmt const * const *getStmts() const {
-    return reinterpret_cast<Stmt const * const*>(this + 1);
-  }
-  Stmt **getStmts() {
-    return reinterpret_cast<Stmt **>(this + 1);
-  }
+  Stmt *const *getStmts() const { return getTrailingObjects<Stmt *>(); }
+  Stmt **getStmts() { return getTrailingObjects<Stmt *>(); }
 
 public:
   static CXXTryStmt *Create(const ASTContext &C, SourceLocation tryLoc,
                             Stmt *tryBlock, ArrayRef<Stmt*> handlers);
 
   static CXXTryStmt *Create(const ASTContext &C, EmptyShell Empty,
                             unsigned numHandlers);
 
public:
 
   static bool classof(const Stmt *T) {
     return T->getStmtClass() == CXXTryStmtClass;
   }
 
   child_range children() {
     return child_range(getStmts(), getStmts() + getNumHandlers() + 1);
   }
-
-  friend class ASTStmtReader;
 };
 
 /// CXXForRangeStmt - This represents C++0x [stmt.ranged]'s ranged for
 /// statement, represented as 'for (range-declarator : range-expression)'.
 ///
 /// This is stored in a partially-desugared form to allow full semantic
 /// analysis of the constituent components. The original syntactic components
 /// can be extracted using getLoopVariable and getRangeInit.

lib/AST/StmtCXX.cpp

 QualType CXXCatchStmt::getCaughtType() const {
   if (ExceptionDecl)
     return ExceptionDecl->getType();
   return QualType();
 }
 
 CXXTryStmt *CXXTryStmt::Create(const ASTContext &C, SourceLocation tryLoc,
                                Stmt *tryBlock, ArrayRef<Stmt *> handlers) {
-  std::size_t Size = sizeof(CXXTryStmt);
-  Size += ((handlers.size() + 1) * sizeof(Stmt *));
-
+  const size_t Size = totalSizeToAlloc<Stmt *>(handlers.size() + 1);
   void *Mem = C.Allocate(Size, alignof(CXXTryStmt));
   return new (Mem) CXXTryStmt(tryLoc, tryBlock, handlers);
 }
 
 CXXTryStmt *CXXTryStmt::Create(const ASTContext &C, EmptyShell Empty,
                                unsigned numHandlers) {
-  std::size_t Size = sizeof(CXXTryStmt);
-  Size += ((numHandlers + 1) * sizeof(Stmt *));
-
+  const size_t Size = totalSizeToAlloc<Stmt *>(numHandlers + 1);
   void *Mem = C.Allocate(Size, alignof(CXXTryStmt));
   return new (Mem) CXXTryStmt(Empty, numHandlers);
 }
 
 CXXTryStmt::CXXTryStmt(SourceLocation tryLoc, Stmt *tryBlock,
                        ArrayRef<Stmt *> handlers)
     : Stmt(CXXTryStmtClass), TryLoc(tryLoc), NumHandlers(handlers.size()) {
-  Stmt **Stmts = reinterpret_cast<Stmt **>(this + 1);
+  Stmt **Stmts = getStmts();
   Stmts[0] = tryBlock;
   std::copy(handlers.begin(), handlers.end(), Stmts + 1);
 }
 
 CXXForRangeStmt::CXXForRangeStmt(DeclStmt *Range,
                                  DeclStmt *BeginStmt, DeclStmt *EndStmt,
                                  Expr *Cond, Expr *Inc, DeclStmt *LoopVar,
                                  Stmt *Body, SourceLocation FL,