[demangler][NFC] Rename SwapAndRestore to ScopedOverride

The demangler has a utility class 'SwapAndRestore'. That name is
confusing. It's not swapping anything, and the restore part happens at
the object's destruction. What it's actually doing is allowing a
override of some value that is dynamically accessible within the
lifetime of a lexical scope. Thus rename it to ScopedOverride, and
tweak it's member variable names.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D122606

GitOrigin-RevId: 51f6caf2fbb5118569f2de33a85ffcc52568e0a7

src/demangle/ItaniumDemangle.h

diff --git a/src/demangle/ItaniumDemangle.h b/src/demangle/ItaniumDemangle.h
index fd6835a..36fe26b 100644
--- a/src/demangle/ItaniumDemangle.h
+++ b/src/demangle/ItaniumDemangle.h
@@ -656,7 +656,7 @@
   void printLeft(OutputBuffer &OB) const override {
     if (Printing)
       return;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     std::pair<ReferenceKind, const Node *> Collapsed = collapse(OB);
     if (!Collapsed.second)
       return;
@@ -671,7 +671,7 @@
   void printRight(OutputBuffer &OB) const override {
     if (Printing)
       return;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     std::pair<ReferenceKind, const Node *> Collapsed = collapse(OB);
     if (!Collapsed.second)
       return;
@@ -1180,7 +1180,7 @@
   template<typename Fn> void match(Fn F) const { F(Name, Params); }
 
   void printLeft(OutputBuffer &OB) const override {
-    SwapAndRestore<unsigned> LT(OB.GtIsGt, 0);
+    ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
     OB += "template<";
     Params.printWithComma(OB);
     OB += "> typename ";
@@ -1316,8 +1316,8 @@
 
   void printLeft(OutputBuffer &OB) const override {
     constexpr unsigned Max = std::numeric_limits<unsigned>::max();
-    SwapAndRestore<unsigned> SavePackIdx(OB.CurrentPackIndex, Max);
-    SwapAndRestore<unsigned> SavePackMax(OB.CurrentPackMax, Max);
+    ScopedOverride<unsigned> SavePackIdx(OB.CurrentPackIndex, Max);
+    ScopedOverride<unsigned> SavePackMax(OB.CurrentPackMax, Max);
     size_t StreamPos = OB.getCurrentPosition();
 
     // Print the first element in the pack. If Child contains a ParameterPack,
@@ -1358,7 +1358,7 @@
   NodeArray getParams() { return Params; }
 
   void printLeft(OutputBuffer &OB) const override {
-    SwapAndRestore<unsigned> LT(OB.GtIsGt, 0);
+    ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
     OB += "<";
     Params.printWithComma(OB);
     if (OB.back() == '>')
@@ -1408,38 +1408,38 @@
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     if (Printing)
       return false;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->hasRHSComponent(OB);
   }
   bool hasArraySlow(OutputBuffer &OB) const override {
     if (Printing)
       return false;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->hasArray(OB);
   }
   bool hasFunctionSlow(OutputBuffer &OB) const override {
     if (Printing)
       return false;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->hasFunction(OB);
   }
   const Node *getSyntaxNode(OutputBuffer &OB) const override {
     if (Printing)
       return this;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->getSyntaxNode(OB);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Printing)
       return;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     Ref->printLeft(OB);
   }
   void printRight(OutputBuffer &OB) const override {
     if (Printing)
       return;
-    SwapAndRestore<bool> SavePrinting(Printing, true);
+    ScopedOverride<bool> SavePrinting(Printing, true);
     Ref->printRight(OB);
   }
 };
@@ -1656,7 +1656,7 @@
 
   void printDeclarator(OutputBuffer &OB) const {
     if (!TemplateParams.empty()) {
-      SwapAndRestore<unsigned> LT(OB.GtIsGt, 0);
+      ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
       OB += "<";
       TemplateParams.printWithComma(OB);
       OB += ">";
@@ -1880,7 +1880,7 @@
   void printLeft(OutputBuffer &OB) const override {
     OB += CastKind;
     {
-      SwapAndRestore<unsigned> LT(OB.GtIsGt, 0);
+      ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
       OB += "<";
       To->printLeft(OB);
       if (OB.back() == '>')
@@ -2857,7 +2857,7 @@
     return make<UnnamedTypeName>(Count);
   }
   if (consumeIf("Ul")) {
-    SwapAndRestore<size_t> SwapParams(ParsingLambdaParamsAtLevel,
+    ScopedOverride<size_t> SwapParams(ParsingLambdaParamsAtLevel,
                                       TemplateParams.size());
     ScopedTemplateParamList LambdaTemplateParams(this);
 
@@ -3062,11 +3062,11 @@
   if (const auto *Op = parseOperatorEncoding()) {
     if (Op->getKind() == OperatorInfo::CCast) {
       //              ::= cv <type>    # (cast)
-      SwapAndRestore<bool> SaveTemplate(TryToParseTemplateArgs, false);
+      ScopedOverride<bool> SaveTemplate(TryToParseTemplateArgs, false);
       // If we're parsing an encoding, State != nullptr and the conversion
       // operators' <type> could have a <template-param> that refers to some
       // <template-arg>s further ahead in the mangled name.
-      SwapAndRestore<bool> SavePermit(PermitForwardTemplateReferences,
+      ScopedOverride<bool> SavePermit(PermitForwardTemplateReferences,
                                       PermitForwardTemplateReferences ||
                                           State != nullptr);
       Node *Ty = getDerived().parseType();
@@ -3718,8 +3718,8 @@
       StringView ProtoSourceName = Qual.dropFront(std::strlen("objcproto"));
       StringView Proto;
       {
-        SwapAndRestore<const char *> SaveFirst(First, ProtoSourceName.begin()),
-                                     SaveLast(Last, ProtoSourceName.end());
+        ScopedOverride<const char *> SaveFirst(First, ProtoSourceName.begin()),
+            SaveLast(Last, ProtoSourceName.end());
         Proto = parseBareSourceName();
       }
       if (Proto.empty())
@@ -4199,7 +4199,7 @@
     return nullptr;
   Node *Ty;
   {
-    SwapAndRestore<bool> SaveTemp(TryToParseTemplateArgs, false);
+    ScopedOverride<bool> SaveTemp(TryToParseTemplateArgs, false);
     Ty = getDerived().parseType();
   }
 
@@ -4634,7 +4634,7 @@
       // C Cast: (type)expr
       Node *Ty;
       {
-        SwapAndRestore<bool> SaveTemp(TryToParseTemplateArgs, false);
+        ScopedOverride<bool> SaveTemp(TryToParseTemplateArgs, false);
         Ty = getDerived().parseType();
       }
       if (Ty == nullptr)

src/demangle/Utility.h

diff --git a/src/demangle/Utility.h b/src/demangle/Utility.h
index 1390f14..6e0fa38 100644
--- a/src/demangle/Utility.h
+++ b/src/demangle/Utility.h
@@ -181,21 +181,20 @@
   size_t getBufferCapacity() const { return BufferCapacity; }
 };
 
-template <class T> class SwapAndRestore {
-  T &Restore;
-  T OriginalValue;
+template <class T> class ScopedOverride {
+  T &Loc;
+  T Original;
 
 public:
-  SwapAndRestore(T &Restore_) : SwapAndRestore(Restore_, Restore_) {}
+  ScopedOverride(T &Loc_) : ScopedOverride(Loc_, Loc_) {}
 
-  SwapAndRestore(T &Restore_, T NewVal)
-      : Restore(Restore_), OriginalValue(Restore) {
-    Restore = std::move(NewVal);
+  ScopedOverride(T &Loc_, T NewVal) : Loc(Loc_), Original(Loc_) {
+    Loc_ = std::move(NewVal);
   }
-  ~SwapAndRestore() { Restore = std::move(OriginalValue); }
+  ~ScopedOverride() { Loc = std::move(Original); }
 
-  SwapAndRestore(const SwapAndRestore &) = delete;
-  SwapAndRestore &operator=(const SwapAndRestore &) = delete;
+  ScopedOverride(const ScopedOverride &) = delete;
+  ScopedOverride &operator=(const ScopedOverride &) = delete;
 };
 
 inline bool initializeOutputBuffer(char *Buf, size_t *N, OutputBuffer &OB,