diff --git a/include/swift/SIL/CFG.h b/include/swift/SIL/CFG.h
index 11fb15d760b..9d191656800 100644
--- a/include/swift/SIL/CFG.h
+++ b/include/swift/SIL/CFG.h
@@ -92,7 +92,7 @@ struct GraphTraits<swift::SILFunction *>
 
   static NodeRef getEntryNode(GraphType F) { return &F->front(); }
 
-  typedef pointer_iterator<swift::SILFunction::iterator> nodes_iterator;
+  using nodes_iterator = pointer_iterator<swift::SILFunction::iterator>;
   static nodes_iterator nodes_begin(GraphType F) {
     return nodes_iterator(F->begin());
   }
@@ -104,12 +104,12 @@ struct GraphTraits<swift::SILFunction *>
 
 template <> struct GraphTraits<Inverse<swift::SILFunction*> >
     : public GraphTraits<Inverse<swift::SILBasicBlock*> > {
-  typedef Inverse<swift::SILFunction *> GraphType;
-  typedef NodeRef NodeRef;
+  using GraphType = Inverse<swift::SILFunction *>;
+  using NodeRef = NodeRef;
 
   static NodeRef getEntryNode(GraphType F) { return &F.Graph->front(); }
 
-  typedef pointer_iterator<swift::SILFunction::iterator> nodes_iterator;
+  using nodes_iterator = pointer_iterator<swift::SILFunction::iterator>;
   static nodes_iterator nodes_begin(GraphType F) {
     return nodes_iterator(F.Graph->begin());
   }
diff --git a/include/swift/SIL/Dominance.h b/include/swift/SIL/Dominance.h
index 091a9a60ac9..505c1cd9749 100644
--- a/include/swift/SIL/Dominance.h
+++ b/include/swift/SIL/Dominance.h
@@ -192,7 +192,7 @@ namespace llvm {
 /// iterable by generic graph iterators.
 template <> struct GraphTraits<swift::DominanceInfoNode *> {
   using ChildIteratorType = swift::DominanceInfoNode::iterator;
-  typedef swift::DominanceInfoNode *NodeRef;
+  using NodeRef = swift::DominanceInfoNode *;
 
   static NodeRef getEntryNode(NodeRef N) { return N; }
   static inline ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
@@ -201,7 +201,7 @@ template <> struct GraphTraits<swift::DominanceInfoNode *> {
 
 template <> struct GraphTraits<const swift::DominanceInfoNode *> {
   using ChildIteratorType = swift::DominanceInfoNode::const_iterator;
-  typedef const swift::DominanceInfoNode *NodeRef;
+  using NodeRef = const swift::DominanceInfoNode *;
 
   static NodeRef getEntryNode(NodeRef N) { return N; }
   static inline ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
diff --git a/include/swift/SIL/PatternMatch.h b/include/swift/SIL/PatternMatch.h
index 793de6d9b4c..87410237943 100644
--- a/include/swift/SIL/PatternMatch.h
+++ b/include/swift/SIL/PatternMatch.h
@@ -140,17 +140,17 @@ struct OneOf_match;
 
 template <typename T0>
 struct OneOf_match<T0> {
-  typedef T0 Ty;
+  using Ty = T0;
 };
 
 template <typename T0, typename T1>
 struct OneOf_match<T0, T1> {
-  typedef match_combine_or<T0, T1> Ty;
+  using Ty = match_combine_or<T0, T1>;
 };
 
 template <typename T0, typename T1, typename ...Arguments>
 struct OneOf_match<T0, T1, Arguments ...> {
-  typedef typename OneOf_match<match_combine_or<T0, T1>, Arguments ...>::Ty Ty;
+  using Ty = typename OneOf_match<match_combine_or<T0, T1>, Arguments...>::Ty;
 };
 
 /// This is a vararg version of m_CombineOr. It is a boolean "or" of
@@ -584,18 +584,18 @@ struct Apply_match;
 
 template <typename CalleeTy>
 struct Apply_match<CalleeTy> {
-  typedef Callee_match<CalleeTy> Ty;
+  using Ty = Callee_match<CalleeTy>;
 };
 
 template <typename CalleeTy, typename T0>
 struct Apply_match<CalleeTy, T0> {
-  typedef match_combine_and<Callee_match<CalleeTy>, Argument_match<T0>> Ty;
+  using Ty = match_combine_and<Callee_match<CalleeTy>, Argument_match<T0>>;
 };
 
 template <typename CalleeTy, typename T0, typename ...Arguments>
 struct Apply_match<CalleeTy, T0, Arguments ...> {
-  typedef match_combine_and<typename Apply_match<CalleeTy, Arguments ...>::Ty,
-                            Argument_match<T0> > Ty;
+  using Ty = match_combine_and<typename Apply_match<CalleeTy, Arguments...>::Ty,
+                               Argument_match<T0>>;
 };
 
 /// Match only an ApplyInst's Callee.
diff --git a/include/swift/SIL/SILCoverageMap.h b/include/swift/SIL/SILCoverageMap.h
index 4174797ff25..a0e41c3b61d 100644
--- a/include/swift/SIL/SILCoverageMap.h
+++ b/include/swift/SIL/SILCoverageMap.h
@@ -145,7 +145,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILCoverageMap>
     : public ilist_default_traits<::swift::SILCoverageMap> {
-  typedef ::swift::SILCoverageMap SILCoverageMap;
+  using SILCoverageMap = ::swift::SILCoverageMap;
 
 public:
   static void deleteNode(SILCoverageMap *VT) { VT->~SILCoverageMap(); }
diff --git a/include/swift/SIL/SILDebuggerClient.h b/include/swift/SIL/SILDebuggerClient.h
index 7c097067e1b..e6c2bf7a2bd 100644
--- a/include/swift/SIL/SILDebuggerClient.h
+++ b/include/swift/SIL/SILDebuggerClient.h
@@ -27,7 +27,7 @@ class SILBuilder;
 
 class SILDebuggerClient : public DebuggerClient {
 public:
-  typedef SmallVectorImpl<LookupResultEntry> ResultVector;
+  using ResultVector = SmallVectorImpl<LookupResultEntry>;
 
   SILDebuggerClient(ASTContext &C) : DebuggerClient(C) { }
   virtual ~SILDebuggerClient() = default;
diff --git a/include/swift/SIL/SILDeclRef.h b/include/swift/SIL/SILDeclRef.h
index 133e501520a..38b00d67412 100644
--- a/include/swift/SIL/SILDeclRef.h
+++ b/include/swift/SIL/SILDeclRef.h
@@ -80,8 +80,8 @@ enum ForDefinition_t : bool {
 /// declaration, such as uncurry levels of a function, the allocating and
 /// initializing entry points of a constructor, etc.
 struct SILDeclRef {
-  typedef llvm::PointerUnion<ValueDecl *, AbstractClosureExpr *> Loc;
-  
+  using Loc = llvm::PointerUnion<ValueDecl *, AbstractClosureExpr *>;
+
   /// Represents the "kind" of the SILDeclRef. For some Swift decls there
   /// are multiple SIL entry points, and the kind is used to distinguish them.
   enum class Kind : unsigned {
diff --git a/include/swift/SIL/SILDefaultWitnessTable.h b/include/swift/SIL/SILDefaultWitnessTable.h
index 1c747b2e678..0a95ef2e994 100644
--- a/include/swift/SIL/SILDefaultWitnessTable.h
+++ b/include/swift/SIL/SILDefaultWitnessTable.h
@@ -174,7 +174,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILDefaultWitnessTable> :
 public ilist_default_traits<::swift::SILDefaultWitnessTable> {
-  typedef ::swift::SILDefaultWitnessTable SILDefaultWitnessTable;
+  using SILDefaultWitnessTable = ::swift::SILDefaultWitnessTable;
 
 public:
   static void deleteNode(SILDefaultWitnessTable *WT) { WT->~SILDefaultWitnessTable(); }
diff --git a/include/swift/SIL/SILFunction.h b/include/swift/SIL/SILFunction.h
index a929b202a42..f4d4e2870f7 100644
--- a/include/swift/SIL/SILFunction.h
+++ b/include/swift/SIL/SILFunction.h
@@ -97,7 +97,7 @@ private:
 class SILFunction
   : public llvm::ilist_node<SILFunction>, public SILAllocated<SILFunction> {
 public:
-  typedef llvm::iplist<SILBasicBlock> BlockListType;
+  using BlockListType = llvm::iplist<SILBasicBlock>;
 
 private:
   friend class SILBasicBlock;
@@ -694,9 +694,9 @@ public:
   BlockListType &getBlocks() { return BlockList; }
   const BlockListType &getBlocks() const { return BlockList; }
 
-  typedef BlockListType::iterator iterator;
-  typedef BlockListType::reverse_iterator reverse_iterator;
-  typedef BlockListType::const_iterator const_iterator;
+  using iterator = BlockListType::iterator;
+  using reverse_iterator = BlockListType::reverse_iterator;
+  using const_iterator = BlockListType::const_iterator;
 
   bool empty() const { return BlockList.empty(); }
   iterator begin() { return BlockList.begin(); }
@@ -881,7 +881,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILFunction> :
 public ilist_default_traits<::swift::SILFunction> {
-  typedef ::swift::SILFunction SILFunction;
+  using SILFunction = ::swift::SILFunction;
 
 public:
   static void deleteNode(SILFunction *V) { V->~SILFunction(); }
diff --git a/include/swift/SIL/SILGlobalVariable.h b/include/swift/SIL/SILGlobalVariable.h
index de41c5231fe..a1d07bbb497 100644
--- a/include/swift/SIL/SILGlobalVariable.h
+++ b/include/swift/SIL/SILGlobalVariable.h
@@ -214,7 +214,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILGlobalVariable> :
 public ilist_default_traits<::swift::SILGlobalVariable> {
-  typedef ::swift::SILGlobalVariable SILGlobalVariable;
+  using SILGlobalVariable = ::swift::SILGlobalVariable;
 
 public:
   static void deleteNode(SILGlobalVariable *V) {}
diff --git a/include/swift/SIL/SILInstruction.h b/include/swift/SIL/SILInstruction.h
index f062aa7f9f0..5b406b3c0bb 100644
--- a/include/swift/SIL/SILInstruction.h
+++ b/include/swift/SIL/SILInstruction.h
@@ -1081,8 +1081,8 @@ class InstructionBaseWithTrailingOperands
 protected:
   friend llvm::TrailingObjects<Derived, Operand, OtherTrailingTypes...>;
 
-  typedef llvm::TrailingObjects<Derived, Operand, OtherTrailingTypes...>
-      TrailingObjects;
+  using TrailingObjects =
+      llvm::TrailingObjects<Derived, Operand, OtherTrailingTypes...>;
 
   using TrailingObjects::totalSizeToAlloc;
 
@@ -1158,8 +1158,9 @@ protected:
   friend InstructionBaseWithTrailingOperands<Kind, Derived, Operand,
                                              OtherTrailingTypes...>;
 
-  typedef InstructionBaseWithTrailingOperands<
-      Kind, Derived, Operand, OtherTrailingTypes...> TrailingObjects;
+  using TrailingObjects =
+      InstructionBaseWithTrailingOperands<Kind, Derived, Operand,
+                                          OtherTrailingTypes...>;
 
 public:
   template <typename... Args>
diff --git a/include/swift/SIL/SILLocation.h b/include/swift/SIL/SILLocation.h
index d3f44f3e590..fb8418c31f1 100644
--- a/include/swift/SIL/SILLocation.h
+++ b/include/swift/SIL/SILLocation.h
@@ -65,7 +65,7 @@ private:
     using type = Pattern;
   };
 
-  typedef llvm::PointerUnion4<Stmt*, Expr*, Decl*, Pattern*> ASTNodeTy;
+  using ASTNodeTy = llvm::PointerUnion4<Stmt *, Expr *, Decl *, Pattern *>;
 
 public:
   enum LocationKind : unsigned {
@@ -419,7 +419,7 @@ public:
   }
 
   /// Fingerprint a DebugLoc for use in a DenseMap.
-  typedef std::pair<std::pair<unsigned, unsigned>, StringRef> DebugLocKey;
+  using DebugLocKey = std::pair<std::pair<unsigned, unsigned>, StringRef>;
   struct DebugLocHash : public DebugLocKey {
     DebugLocHash(DebugLoc L) : DebugLocKey({{L.Line, L.Column}, L.Filename}) {}
   };
diff --git a/include/swift/SIL/SILModule.h b/include/swift/SIL/SILModule.h
index fcb0c91ec78..d88c7bbacd4 100644
--- a/include/swift/SIL/SILModule.h
+++ b/include/swift/SIL/SILModule.h
@@ -217,7 +217,7 @@ private:
   // Callbacks registered by the SIL optimizer to run on each deserialized
   // function body. This is intentionally a stateless type because the
   // ModuleDecl and SILFunction should be sufficient context.
-  typedef void (*SILFunctionBodyCallback)(ModuleDecl *, SILFunction *F);
+  using SILFunctionBodyCallback = void (*)(ModuleDecl *, SILFunction *F);
   SmallVector<SILFunctionBodyCallback, 0> DeserializationCallbacks;
 
   /// The SILLoader used when linking functions into this module.
diff --git a/include/swift/SIL/SILProperty.h b/include/swift/SIL/SILProperty.h
index a59c3f415c1..3a3c46b5d36 100644
--- a/include/swift/SIL/SILProperty.h
+++ b/include/swift/SIL/SILProperty.h
@@ -79,7 +79,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILProperty>
     : public ilist_default_traits<::swift::SILProperty> {
-  typedef ::swift::SILProperty SILProperty;
+  using SILProperty = ::swift::SILProperty;
 
 public:
   static void deleteNode(SILProperty *VT) { VT->~SILProperty(); }
diff --git a/include/swift/SIL/SILVTable.h b/include/swift/SIL/SILVTable.h
index fb9cc7235b4..285b3f7435d 100644
--- a/include/swift/SIL/SILVTable.h
+++ b/include/swift/SIL/SILVTable.h
@@ -174,7 +174,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILVTable> :
 public ilist_default_traits<::swift::SILVTable> {
-  typedef ::swift::SILVTable SILVTable;
+  using SILVTable = ::swift::SILVTable;
 
   static void deleteNode(SILVTable *VT) { VT->~SILVTable(); }
 
diff --git a/include/swift/SIL/SILValue.h b/include/swift/SIL/SILValue.h
index dedf7539c7a..d7d14ba5fe7 100644
--- a/include/swift/SIL/SILValue.h
+++ b/include/swift/SIL/SILValue.h
@@ -440,7 +440,7 @@ private:
 inline SILValue getSILValueType(const Operand &op) {
   return op.get();
 }
-typedef ArrayRefView<Operand,SILValue,getSILValueType> OperandValueArrayRef;
+using OperandValueArrayRef = ArrayRefView<Operand, SILValue, getSILValueType>;
 
 /// An iterator over all uses of a ValueBase.
 class ValueBaseUseIterator : public std::iterator<std::forward_iterator_tag,
@@ -600,7 +600,7 @@ inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, SILValue V) {
 namespace llvm {
   /// A SILValue casts like a ValueBase *.
   template<> struct simplify_type<const ::swift::SILValue> {
-    typedef ::swift::ValueBase *SimpleType;
+    using SimpleType = ::swift::ValueBase *;
     static SimpleType getSimplifiedValue(::swift::SILValue Val) {
       return Val;
     }
diff --git a/include/swift/SIL/SILWitnessTable.h b/include/swift/SIL/SILWitnessTable.h
index 6e509544072..6de1914aa74 100644
--- a/include/swift/SIL/SILWitnessTable.h
+++ b/include/swift/SIL/SILWitnessTable.h
@@ -318,7 +318,7 @@ namespace llvm {
 template <>
 struct ilist_traits<::swift::SILWitnessTable> :
 public ilist_default_traits<::swift::SILWitnessTable> {
-  typedef ::swift::SILWitnessTable SILWitnessTable;
+  using SILWitnessTable = ::swift::SILWitnessTable;
 
 public:
   static void deleteNode(SILWitnessTable *WT) { WT->~SILWitnessTable(); }
diff --git a/include/swift/SIL/TypeLowering.h b/include/swift/SIL/TypeLowering.h
index 09fa63a308d..26990c6cc4e 100644
--- a/include/swift/SIL/TypeLowering.h
+++ b/include/swift/SIL/TypeLowering.h
@@ -938,7 +938,7 @@ private:
 
 namespace llvm {
   template<> struct DenseMapInfo<swift::Lowering::TypeConverter::CachingTypeKey> {
-    typedef swift::Lowering::TypeConverter::CachingTypeKey CachingTypeKey;
+    using CachingTypeKey = swift::Lowering::TypeConverter::CachingTypeKey;
 
     using APCachingKey = swift::Lowering::AbstractionPattern::CachingKey;
     using CachingKeyInfo = DenseMapInfo<APCachingKey>;
@@ -967,7 +967,7 @@ namespace llvm {
   };
 
   template<> struct DenseMapInfo<swift::Lowering::TypeConverter::OverrideKey> {
-    typedef swift::Lowering::TypeConverter::OverrideKey OverrideKey;
+    using OverrideKey = swift::Lowering::TypeConverter::OverrideKey;
 
     using SILDeclRefInfo = DenseMapInfo<swift::SILDeclRef>;
 
diff --git a/include/swift/SIL/TypeSubstCloner.h b/include/swift/SIL/TypeSubstCloner.h
index b5b4ae4609d..4f857e9d058 100644
--- a/include/swift/SIL/TypeSubstCloner.h
+++ b/include/swift/SIL/TypeSubstCloner.h
@@ -34,7 +34,7 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
   friend class SILInstructionVisitor<ImplClass>;
   friend class SILCloner<ImplClass>;
 
-  typedef SILClonerWithScopes<ImplClass> super;
+  using super = SILClonerWithScopes<ImplClass>;
 
   void postProcess(SILInstruction *Orig, SILInstruction *Cloned) {
     llvm_unreachable("Clients need to explicitly call a base class impl!");
diff --git a/lib/Serialization/Serialization.cpp b/lib/Serialization/Serialization.cpp
index f0102db6924..e8d99b9c3cb 100644
--- a/lib/Serialization/Serialization.cpp
+++ b/lib/Serialization/Serialization.cpp
@@ -4386,8 +4386,8 @@ public:
 
 } // 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;
diff --git a/lib/Serialization/Serialization.h b/lib/Serialization/Serialization.h
index 340f88a235d..c571c3b0991 100644
--- a/lib/Serialization/Serialization.h
+++ b/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;
diff --git a/lib/Serialization/SerializedModuleLoader.cpp b/lib/Serialization/SerializedModuleLoader.cpp
index eac4d4ce801..bd3ade2871a 100644
--- a/lib/Serialization/SerializedModuleLoader.cpp
+++ b/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.