Use llvm::StringSet instead of StringMap where appropriate

That is, where we aren't using the value for anything.

No functionality change.

Author: jrose-apple

lib/AST/ASTContext.cpp

@@ -124,6 +124,8 @@ struct ASTContext::Implementation {
   /// lazy parsers for imported module files and source files.
   llvm::SmallPtrSet<LazyMemberParser*, 2> lazyParsers;
 
+  // FIXME: This is a StringMap rather than a StringSet because StringSet
+  // doesn't allow passing in a pre-existing allocator.
   llvm::StringMap<char, llvm::BumpPtrAllocator&> IdentifierTable;
 
   /// The declaration of Swift.AssignmentPrecedence.

lib/IDE/Refactoring.cpp

@@ -387,15 +387,17 @@ class RenameRangeDetailCollector : public Renamer {
 };
 
 class TextReplacementsRenamer : public Renamer {
-  llvm::StringMap<char> &ReplaceTextContext;
+  llvm::StringSet<> &ReplaceTextContext;
   std::vector<Replacement> Replacements;
 
 public:
   const DeclNameViewer New;
 
 private:
   StringRef registerText(StringRef Text) {
-    return ReplaceTextContext.insert({Text, char()}).first->getKey();
+    if (Text.empty())
+      return Text;
+    return ReplaceTextContext.insert(Text).first->getKey();
   }
 
   StringRef getCallArgLabelReplacement(StringRef OldLabelRange,
@@ -497,7 +499,7 @@ class TextReplacementsRenamer : public Renamer {
 public:
   TextReplacementsRenamer(const SourceManager &SM, StringRef OldName,
                           StringRef NewName,
-                          llvm::StringMap<char> &ReplaceTextContext)
+                          llvm::StringSet<> &ReplaceTextContext)
       : Renamer(SM, OldName), ReplaceTextContext(ReplaceTextContext),
         New(NewName) {
     assert(Old.isValid() && New.isValid());
@@ -3285,7 +3287,7 @@ int swift::ide::syntacticRename(SourceFile *SF, ArrayRef<RenameLoc> RenameLocs,
     return true; // Already diagnosed.
 
   size_t index = 0;
-  llvm::StringMap<char> ReplaceTextContext;
+  llvm::StringSet<> ReplaceTextContext;
   for(const RenameLoc &Rename: RenameLocs) {
     ResolvedLoc &Resolved = ResolvedLocs[index++];
     TextReplacementsRenamer Renamer(SM, Rename.OldName, Rename.NewName,

lib/Serialization/SerializedModuleLoader.cpp

@@ -20,6 +20,7 @@
 #include "swift/Basic/SourceManager.h"
 #include "swift/Basic/Version.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
@@ -376,19 +377,15 @@ FileUnit *SerializedModuleLoader::loadAST(
     // Figure out /which/ dependencies are missing.
     // FIXME: Dependencies should be de-duplicated at serialization time,
     // not now.
-    llvm::StringMap<bool> duplicates;
+    llvm::StringSet<> duplicates;
     llvm::SmallVector<ModuleFile::Dependency, 4> missing;
     std::copy_if(loadedModuleFile->getDependencies().begin(),
                  loadedModuleFile->getDependencies().end(),
                  std::back_inserter(missing),
                  [&duplicates](const ModuleFile::Dependency &dependency)->bool {
       if (dependency.isLoaded() || dependency.isHeader())
         return false;
-      bool &seen = duplicates[dependency.RawPath];
-      if (seen)
-        return false;
-      seen = true;
-      return true;
+      return duplicates.insert(dependency.RawPath).second;
     });
 
     // FIXME: only show module part of RawAccessPath