[SourceKit] Hold CompletionInstance with std::shared_ptr

So we can pin it on the threads.

Author: rintaro

tools/SourceKit/lib/SwiftLang/SwiftCompletion.cpp

@@ -172,7 +172,10 @@ static bool swiftCodeCompleteImpl(
     Error = "no input filenames specified";
     return false;
   }
-  CompilerInstance *CI = Lang.getCompletionInstance().getCompilerInstance(
+
+  // Pin completion instance.
+  auto CompletionInst =  Lang.getCompletionInstance();
+  CompilerInstance *CI = CompletionInst->getCompilerInstance(
       Invocation, FileSystem, newBuffer.get(), Offset, Error, &CIDiags);
   if (!CI)
     return false;

tools/SourceKit/lib/SwiftLang/SwiftConformingMethodList.cpp

@@ -76,7 +76,10 @@ static bool swiftConformingMethodListImpl(
     Error = "no input filenames specified";
     return false;
   }
-  CompilerInstance *CI = Lang.getCompletionInstance().getCompilerInstance(
+
+  // Pin completion instance.
+  auto CompletionInst =  Lang.getCompletionInstance();
+  CompilerInstance *CI = CompletionInst->getCompilerInstance(
       Invocation, FileSystem, newBuffer.get(), Offset, Error, &CIDiags);
   if (!CI)
     return false;

tools/SourceKit/lib/SwiftLang/SwiftLangSupport.h

@@ -295,7 +295,7 @@ class SwiftLangSupport : public LangSupport {
   ThreadSafeRefCntPtr<SwiftCustomCompletions> CustomCompletions;
   std::shared_ptr<SwiftStatistics> Stats;
   llvm::StringMap<std::unique_ptr<FileSystemProvider>> FileSystemProviders;
-  std::unique_ptr<swift::ide::CompletionInstance> CompletionInst;
+  std::shared_ptr<swift::ide::CompletionInstance> CompletionInst;
 
 public:
   explicit SwiftLangSupport(SourceKit::Context &SKCtx);
@@ -315,8 +315,8 @@ class SwiftLangSupport : public LangSupport {
     return CCCache;
   }
 
-  swift::ide::CompletionInstance &getCompletionInstance() {
-    return *CompletionInst;
+  std::shared_ptr<swift::ide::CompletionInstance> getCompletionInstance() {
+    return CompletionInst;
   }
 
   /// Returns the FileSystemProvider registered under Name, or nullptr if not

tools/SourceKit/lib/SwiftLang/SwiftTypeContextInfo.cpp

@@ -74,7 +74,10 @@ static bool swiftTypeContextInfoImpl(
     Error = "no input filenames specified";
     return false;
   }
-  CompilerInstance *CI = Lang.getCompletionInstance().getCompilerInstance(
+
+  // Pin completion instance.
+  auto CompletionInst =  Lang.getCompletionInstance();
+  CompilerInstance *CI = CompletionInst->getCompilerInstance(
       Invocation, FileSystem, newBuffer.get(), Offset, Error, &CIDiags);
   if (!CI)
     return false;