[NFC] Fixup InputFile Convenience Getters

Follow programming guidelines for these getters more closely and have them return a non-owning view of the underlying data instead of relying on callers to take const references to the copy that is returned here.

include/swift/Frontend/InputFile.h

@@ -121,17 +121,17 @@ public:
   // FrontendInputsAndOutputs. They merely make the call sites
   // a bit shorter. Add more forwarding methods as needed.
 
-  std::string dependenciesFilePath() const {
+  StringRef getDependenciesFilePath() const {
     return getPrimarySpecificPaths().SupplementaryOutputs.DependenciesFilePath;
   }
-  std::string loadedModuleTracePath() const {
+  StringRef getLoadedModuleTracePath() const {
     return getPrimarySpecificPaths().SupplementaryOutputs.LoadedModuleTracePath;
   }
-  std::string serializedDiagnosticsPath() const {
+  StringRef getSerializedDiagnosticsPath() const {
     return getPrimarySpecificPaths().SupplementaryOutputs
         .SerializedDiagnosticsPath;
   }
-  std::string fixItsOutputPath() const {
+  StringRef getFixItsOutputPath() const {
     return getPrimarySpecificPaths().SupplementaryOutputs.FixItsOutputPath;
   }
 };

lib/FrontendTool/FrontendTool.cpp

@@ -127,7 +127,7 @@ getFileOutputStream(StringRef OutputFilename, ASTContext &Ctx) {
 }
 
 /// Writes the Syntax tree to the given file
-static bool emitSyntax(SourceFile &SF, StringRef OutputFilename) {
+static bool emitSyntax(const SourceFile &SF, StringRef OutputFilename) {
   auto os = getFileOutputStream(OutputFilename, SF.getASTContext());
   if (!os) return true;
 
@@ -221,7 +221,7 @@ class JSONFixitWriter
 public:
   JSONFixitWriter(std::string fixitsOutputPath,
                   const DiagnosticOptions &DiagOpts)
-    : FixitsOutputPath(fixitsOutputPath),
+      : FixitsOutputPath(std::move(fixitsOutputPath)),
         FixitAll(DiagOpts.FixitCodeForAllDiagnostics) {}
 
 private:
@@ -1612,10 +1612,13 @@ static void emitIndexDataForSourceFile(SourceFile *PrimarySourceFile,
     if (moduleToken.empty())
       moduleToken = opts.InputsAndOutputs.getSingleOutputFilename();
 
-    (void) index::indexAndRecord(Instance.getMainModule(), opts.InputsAndOutputs.copyOutputFilenames(),
+    (void) index::indexAndRecord(Instance.getMainModule(),
+                                 opts.InputsAndOutputs.copyOutputFilenames(),
                                  moduleToken, opts.IndexStorePath,
-                                 opts.IndexSystemModules, opts.IndexIgnoreStdlib,
-                                 isDebugCompilation, Invocation.getTargetTriple(),
+                                 opts.IndexSystemModules,
+                                 opts.IndexIgnoreStdlib,
+                                 isDebugCompilation,
+                                 Invocation.getTargetTriple(),
                                  *Instance.getDependencyTracker());
   }
 }
@@ -1683,10 +1686,11 @@ createSerializedDiagnosticConsumerIfNeeded(
   return createDispatchingDiagnosticConsumerIfNeeded(
       inputsAndOutputs,
       [](const InputFile &input) -> std::unique_ptr<DiagnosticConsumer> {
-    std::string serializedDiagnosticsPath = input.serializedDiagnosticsPath();
+        auto serializedDiagnosticsPath = input.getSerializedDiagnosticsPath();
         if (serializedDiagnosticsPath.empty())
           return nullptr;
-    return serialized_diagnostics::createConsumer(serializedDiagnosticsPath);
+        return serialized_diagnostics::createConsumer(
+            serializedDiagnosticsPath);
       });
 }
 
@@ -1704,11 +1708,11 @@ createJSONFixItDiagnosticConsumerIfNeeded(
   return createDispatchingDiagnosticConsumerIfNeeded(
       invocation.getFrontendOptions().InputsAndOutputs,
       [&](const InputFile &input) -> std::unique_ptr<DiagnosticConsumer> {
-    std::string fixItsOutputPath = input.fixItsOutputPath();
+        auto fixItsOutputPath = input.getFixItsOutputPath();
         if (fixItsOutputPath.empty())
           return nullptr;
         return std::make_unique<JSONFixitWriter>(
-        fixItsOutputPath, invocation.getDiagnosticOptions());
+            fixItsOutputPath.str(), invocation.getDiagnosticOptions());
       });
 }
 

lib/FrontendTool/LoadedModuleTrace.cpp

@@ -699,7 +699,7 @@ bool swift::emitLoadedModuleTraceIfNeeded(ModuleDecl *mainModule,
   assert(!ctxt.hadError() &&
          "We should've already exited earlier if there was an error.");
 
-  auto loadedModuleTracePath = input.loadedModuleTracePath();
+  auto loadedModuleTracePath = input.getLoadedModuleTracePath();
   if (loadedModuleTracePath.empty())
     return false;
   std::error_code EC;

lib/FrontendTool/MakeStyleDependencies.cpp

@@ -91,7 +91,7 @@ bool swift::emitMakeDependenciesIfNeeded(DiagnosticEngine &diags,
                                          DependencyTracker *depTracker,
                                          const FrontendOptions &opts,
                                          const InputFile &input) {
-  const std::string &dependenciesFilePath = input.dependenciesFilePath();
+  auto dependenciesFilePath = input.getDependenciesFilePath();
   if (dependenciesFilePath.empty())
     return false;