[clang] Store code completion token range in preprocessor.

Summary:
This change is to support a new fature in clangd, tests will be send toclang-tools-extra with that change.

Unittests are included in: https://reviews.llvm.org/D50449

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: ioeric, MaskRay, jkorous, arphaman, cfe-commits

Differential Revision: https://reviews.llvm.org/D50443

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@339540 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Lex/Preprocessor.h

@@ -310,6 +310,9 @@ class Preprocessor {
   /// on the stem that is to be code completed.
   IdentifierInfo *CodeCompletionII = nullptr;
 
+  /// Range for the code completion token.
+  SourceRange CodeCompletionTokenRange;
+
   /// The directory that the main file should be considered to occupy,
   /// if it does not correspond to a real file (as happens when building a
   /// module).
@@ -1131,6 +1134,16 @@ public:
     CodeCompletionII = Filter;
   }
 
+  /// Set the code completion token range for detecting replacement range later
+  /// on.
+  void setCodeCompletionTokenRange(const SourceLocation Start,
+                                   const SourceLocation End) {
+    CodeCompletionTokenRange = {Start, End};
+  }
+  SourceRange getCodeCompletionTokenRange() const {
+    return CodeCompletionTokenRange;
+  }
+
   /// Get the code completion token for filtering purposes.
   StringRef getCodeCompletionFilter() {
     if (CodeCompletionII)

lib/Lex/Preprocessor.cpp

@@ -868,6 +868,7 @@ void Preprocessor::Lex(Token &Result) {
   if (Result.is(tok::code_completion) && Result.getIdentifierInfo()) {
     // Remember the identifier before code completion token.
     setCodeCompletionIdentifierInfo(Result.getIdentifierInfo());
+    setCodeCompletionTokenRange(Result.getLocation(), Result.getEndLoc());
     // Set IdenfitierInfo to null to avoid confusing code that handles both
     // identifiers and completion tokens.
     Result.setIdentifierInfo(nullptr);