Merge pull request #15591 from ikesyo/demangling-using-over-typedef

[gardening][Demangling] Replace `typedef` with `using`

Author: ikesyo

include/swift/Demangling/Demangle.h

@@ -75,7 +75,7 @@ struct DemangleOptions {
 };
 
 class Node;
-typedef Node *NodePointer;
+using NodePointer = Node *;
 
 enum class FunctionSigSpecializationParamKind : unsigned {
   // Option Flags use bits 0-5. This give us 6 bits implying 64 entries to
@@ -133,7 +133,7 @@ class Node {
 #include "swift/Demangling/DemangleNodes.def"
   };
 
-  typedef uint64_t IndexType;
+  using IndexType = uint64_t;
 
   friend class NodeFactory;
 
@@ -182,10 +182,10 @@ class Node {
     assert(hasIndex());
     return IndexPayload;
   }
-  
-  typedef NodePointer *iterator;
-  typedef const NodePointer *const_iterator;
-  typedef size_t size_type;
+
+  using iterator = NodePointer *;
+  using const_iterator = const NodePointer *;
+  using size_type = size_t;
 
   bool hasChildren() const { return NumChildren != 0; }
   size_t getNumChildren() const { return NumChildren; }

include/swift/Demangling/Demangler.h

@@ -207,8 +207,7 @@ template<typename T> class Vector {
   size_t Capacity = 0;
 
 public:
-  
-  typedef T *iterator;
+  using iterator = T *;
 
   Vector() { }