[CodeCompletion Remember the replaced source range in SourceManager

Author: rintaro

include/swift/Basic/SourceManager.h

@@ -38,6 +38,20 @@ class SourceManager {
   /// to speed up stats.
   mutable llvm::DenseMap<StringRef, llvm::vfs::Status> StatusCache;
 
+  struct ReplacedRangeType {
+    SourceRange Original;
+    SourceRange New;
+    ReplacedRangeType() {}
+    ReplacedRangeType(NoneType) {}
+    ReplacedRangeType(SourceRange Original, SourceRange New)
+        : Original(Original), New(New) {
+      assert(Original.isValid() && New.isValid());
+    }
+
+    explicit operator bool() const { return Original.isValid(); }
+  };
+  ReplacedRangeType ReplacedRange;
+
   // \c #sourceLocation directive handling.
   struct VirtualFile {
     CharSourceRange Range;
@@ -89,6 +103,9 @@ class SourceManager {
 
   SourceLoc getCodeCompletionLoc() const;
 
+  const ReplacedRangeType &getReplacedRange() const { return ReplacedRange; }
+  void setReplacedRange(const ReplacedRangeType &val) { ReplacedRange = val; }
+
   /// Returns true if \c LHS is before \c RHS in the source buffer.
   bool isBeforeInBuffer(SourceLoc LHS, SourceLoc RHS) const {
     return LHS.Value.getPointer() < RHS.Value.getPointer();

lib/IDE/CompletionInstance.cpp

@@ -417,6 +417,7 @@ bool CompletionInstance::performCachedOperationIfPossible(
 
     auto *AFD = cast<AbstractFunctionDecl>(DC);
     AFD->setBodyToBeReparsed(newBodyRange);
+    SM.setReplacedRange({AFD->getOriginalBodySourceRange(), newBodyRange});
 
     traceDC = AFD;
     break;