Merge pull request #15758 from ikesyo/serialization-using-over-typedef

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

Author: DougGregor

lib/Serialization/Serialization.cpp

@@ -4379,8 +4379,8 @@ class DeclCommentTableInfo {
 
 } // end unnamed namespace
 
-typedef llvm::StringMap<std::string> FileNameToGroupNameMap;
-typedef std::unique_ptr<FileNameToGroupNameMap> pFileNameToGroupNameMap;
+using FileNameToGroupNameMap = llvm::StringMap<std::string>;
+using pFileNameToGroupNameMap = std::unique_ptr<FileNameToGroupNameMap>;
 
 class YamlGroupInputParser {
   StringRef RecordPath;

lib/Serialization/Serialization.h

@@ -32,7 +32,7 @@ namespace swift {
 
 namespace serialization {
 
-typedef ArrayRef<std::string> FilenamesTy;
+using FilenamesTy = ArrayRef<std::string>;
 
 class Serializer {
   SmallVector<char, 0> Buffer;

lib/Serialization/SerializedModuleLoader.cpp

@@ -28,7 +28,7 @@
 using namespace swift;
 
 namespace {
-typedef std::pair<Identifier, SourceLoc> AccessPathElem;
+using AccessPathElem = std::pair<Identifier, SourceLoc>;
 } // end unnamed namespace
 
 // Defined out-of-line so that we can see ~ModuleFile.