Merge remote-tracking branch 'origin/master' into master-next

tools/SourceKit/lib/SwiftLang/SwiftEditor.cpp

@@ -1709,10 +1709,16 @@ ImmutableTextSnapshotRef SwiftEditorDocument::initializeText(
 
 ImmutableTextSnapshotRef SwiftEditorDocument::replaceText(
     unsigned Offset, unsigned Length, llvm::MemoryBuffer *Buf,
-    bool ProvideSemanticInfo) {
+    bool ProvideSemanticInfo, std::string &error) {
 
   llvm::sys::ScopedLock L(Impl.AccessMtx);
 
+  // Validate offset and length.
+  if ((Offset + Length) > Impl.EditableBuffer->getSize()) {
+    error = "'offset' + 'length' is out of range";
+    return nullptr;
+  }
+
   Impl.Edited = true;
   llvm::StringRef Str = Buf->getBuffer();
 
@@ -2236,9 +2242,14 @@ void SwiftLangSupport::editorReplaceText(StringRef Name,
       StringRef PreEditTextRef(BufferStart + Offset, Length);
       PreEditText = PreEditTextRef.str();
     }
+    std::string error;
     Snapshot = EditorDoc->replaceText(Offset, Length, Buf,
-                                      Consumer.needsSemanticInfo());
-    assert(Snapshot);
+                                      Consumer.needsSemanticInfo(), error);
+    if (!Snapshot) {
+      assert(error.size());
+      Consumer.handleRequestError(error.c_str());
+      return;
+    }
 
     llvm::Optional<SyntaxParsingCache> SyntaxCache = llvm::None;
     if (EditorDoc->getSyntaxTree().hasValue()) {