diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
@@ -44,6 +44,15 @@ struct Position {
   /// Character offset on a line in a document (zero-based).
   int character;
 
+  friend bool operator==(const Position &LHS, const Position &RHS) {
+    return std::tie(LHS.line, LHS.character) ==
+           std::tie(RHS.line, RHS.character);
+  }
+  friend bool operator<(const Position &LHS, const Position &RHS) {
+    return std::tie(LHS.line, LHS.character) <
+           std::tie(RHS.line, RHS.character);
+  }
+
   static llvm::Optional<Position> parse(llvm::yaml::MappingNode *Params);
   static std::string unparse(const Position &P);
 };
@@ -55,6 +64,13 @@ struct Range {
   /// The range's end position.
   Position end;
 
+  friend bool operator==(const Range &LHS, const Range &RHS) {
+    return std::tie(LHS.start, LHS.end) == std::tie(RHS.start, RHS.end);
+  }
+  friend bool operator<(const Range &LHS, const Range &RHS) {
+    return std::tie(LHS.start, LHS.end) < std::tie(RHS.start, RHS.end);
+  }
+
   static llvm::Optional<Range> parse(llvm::yaml::MappingNode *Params);
   static std::string unparse(const Range &P);
 };
@@ -172,6 +188,51 @@ struct DocumentFormattingParams {
   parse(llvm::yaml::MappingNode *Params);
 };
 
+struct Diagnostic {
+  /// The range at which the message applies.
+  Range range;
+
+  /// The diagnostic's severity. Can be omitted. If omitted it is up to the
+  /// client to interpret diagnostics as error, warning, info or hint.
+  int severity;
+
+  /// The diagnostic's message.
+  std::string message;
+
+  friend bool operator==(const Diagnostic &LHS, const Diagnostic &RHS) {
+    return std::tie(LHS.range, LHS.severity, LHS.message) ==
+           std::tie(RHS.range, RHS.severity, RHS.message);
+  }
+  friend bool operator<(const Diagnostic &LHS, const Diagnostic &RHS) {
+    return std::tie(LHS.range, LHS.severity, LHS.message) <
+           std::tie(RHS.range, RHS.severity, RHS.message);
+  }
+
+  static llvm::Optional<Diagnostic> parse(llvm::yaml::MappingNode *Params);
+};
+
+struct CodeActionContext {
+  /// An array of diagnostics.
+  std::vector<Diagnostic> diagnostics;
+
+  static llvm::Optional<CodeActionContext>
+  parse(llvm::yaml::MappingNode *Params);
+};
+
+struct CodeActionParams {
+  /// The document in which the command was invoked.
+  TextDocumentIdentifier textDocument;
+
+  /// The range for which the command was invoked.
+  Range range;
+
+  /// Context carrying additional information.
+  CodeActionContext context;
+
+  static llvm::Optional<CodeActionParams>
+  parse(llvm::yaml::MappingNode *Params);
+};
+
 } // namespace clangd
 } // namespace clang
 

diff --git a/clang-tools-extra/clangd/ProtocolHandlers.cpp b/clang-tools-extra/clangd/ProtocolHandlers.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "ProtocolHandlers.h"
+#include "ASTManager.h"
 #include "DocumentStore.h"
 #include "clang/Format/Format.h"
 using namespace clang;
@@ -58,18 +59,9 @@ static Position offsetToPosition(StringRef Code, size_t Offset) {
   return {Lines, Cols};
 }
 
-static std::string formatCode(StringRef Code, StringRef Filename,
-                              ArrayRef<tooling::Range> Ranges, StringRef ID) {
-  // Call clang-format.
-  // FIXME: Don't ignore style.
-  format::FormatStyle Style = format::getLLVMStyle();
-  // On windows FileManager doesn't like file://. Just strip it, clang-format
-  // doesn't need it.
-  Filename.consume_front("file://");
-  tooling::Replacements Replacements =
-      format::reformat(Style, Code, Ranges, Filename);
-
-  // Now turn the replacements into the format specified by the Language Server
+template <typename T>
+static std::string replacementsToEdits(StringRef Code, const T &Replacements) {
+  // Turn the replacements into the format specified by the Language Server
   // Protocol. Fuse them into one big JSON array.
   std::string Edits;
   for (auto &R : Replacements) {
@@ -83,6 +75,21 @@ static std::string formatCode(StringRef Code, StringRef Filename,
   if (!Edits.empty())
     Edits.pop_back();
 
+  return Edits;
+}
+
+static std::string formatCode(StringRef Code, StringRef Filename,
+                              ArrayRef<tooling::Range> Ranges, StringRef ID) {
+  // Call clang-format.
+  // FIXME: Don't ignore style.
+  format::FormatStyle Style = format::getLLVMStyle();
+  // On windows FileManager doesn't like file://. Just strip it, clang-format
+  // doesn't need it.
+  Filename.consume_front("file://");
+  tooling::Replacements Replacements =
+      format::reformat(Style, Code, Ranges, Filename);
+
+  std::string Edits = replacementsToEdits(Code, Replacements);
   return R"({"jsonrpc":"2.0","id":)" + ID.str() +
          R"(,"result":[)" + Edits + R"(]})";
 }
@@ -138,3 +145,36 @@ void TextDocumentFormattingHandler::handleMethod(
   writeMessage(formatCode(Code, DFP->textDocument.uri,
                           {clang::tooling::Range(0, Code.size())}, ID));
 }
+
+void CodeActionHandler::handleMethod(llvm::yaml::MappingNode *Params,
+                                     StringRef ID) {
+  auto CAP = CodeActionParams::parse(Params);
+  if (!CAP) {
+    Output.log("Failed to decode CodeActionParams!\n");
+    return;
+  }
+
+  // We provide a code action for each diagnostic at the requested location
+  // which has FixIts available.
+  std::string Code = AST.getStore().getDocument(CAP->textDocument.uri);
+  std::string Commands;
+  for (Diagnostic &D : CAP->context.diagnostics) {
+    std::vector<clang::tooling::Replacement> Fixes = AST.getFixIts(D);
+    std::string Edits = replacementsToEdits(Code, Fixes);
+
+    if (!Edits.empty())
+      Commands +=
+          R"({"title":"Apply FixIt ')" + llvm::yaml::escape(D.message) +
+          R"('", "command": "clangd.applyFix", "arguments": [")" +
+          llvm::yaml::escape(CAP->textDocument.uri) +
+          R"(", [)" + Edits +
+          R"(]]},)";
+  }
+  if (!Commands.empty())
+    Commands.pop_back();
+
+  writeMessage(
+      R"({"jsonrpc":"2.0","id":)" + ID.str() +
+      R"(, "result": [)" + Commands +
+      R"(]})");
+}
diff --git a/clang-tools-extra/clangd/ProtocolHandlers.h b/clang-tools-extra/clangd/ProtocolHandlers.h
@@ -22,6 +22,7 @@
 
 namespace clang {
 namespace clangd {
+class ASTManager;
 class DocumentStore;
 
 struct InitializeHandler : Handler {
@@ -34,7 +35,8 @@ struct InitializeHandler : Handler {
           "textDocumentSync": 1,
           "documentFormattingProvider": true,
           "documentRangeFormattingProvider": true,
-          "documentOnTypeFormattingProvider": {"firstTriggerCharacter":"}","moreTriggerCharacter":[]}
+          "documentOnTypeFormattingProvider": {"firstTriggerCharacter":"}","moreTriggerCharacter":[]},
+          "codeActionProvider": true
         }}})");
   }
 };
@@ -102,6 +104,16 @@ struct TextDocumentFormattingHandler : Handler {
   DocumentStore &Store;
 };
 
+struct CodeActionHandler : Handler {
+  CodeActionHandler(JSONOutput &Output, ASTManager &AST)
+      : Handler(Output), AST(AST) {}
+
+  void handleMethod(llvm::yaml::MappingNode *Params, StringRef ID) override;
+
+private:
+  ASTManager &AST;
+};
+
 } // namespace clangd
 } // namespace clang
 

diff --git a/clang-tools-extra/clangd/clients/clangd-vscode/src/extension.ts b/clang-tools-extra/clangd/clients/clangd-vscode/src/extension.ts
@@ -18,9 +18,25 @@ export function activate(context: vscode.ExtensionContext) {
 
     const clangdClient = new vscodelc.LanguageClient('Clang Language Server', serverOptions, clientOptions);
 
+    function applyTextEdits(uri: string, edits: vscodelc.TextEdit[]) {
+        let textEditor = vscode.window.activeTextEditor;
+
+        if (textEditor && textEditor.document.uri.toString() === uri) {
+            textEditor.edit(mutator => {
+                for (const edit of edits) {
+                    mutator.replace(vscodelc.Protocol2Code.asRange(edit.range), edit.newText);
+                }
+            }).then((success) => {
+                if (!success) {
+                    vscode.window.showErrorMessage('Failed to apply fixes to the document.');
+                }
+            });
+        }
+    }
+
     console.log('Clang Language Server is now active!');
 
     const disposable = clangdClient.start();
 
-    context.subscriptions.push(disposable);
+    context.subscriptions.push(disposable, vscode.commands.registerCommand('clangd.applyFix', applyTextEdits));
 }
diff --git a/clang-tools-extra/test/clangd/fixits.test b/clang-tools-extra/test/clangd/fixits.test
@@ -0,0 +1,22 @@
+# RUN: clangd -run-synchronously < %s | FileCheck %s
+# It is absolutely vital that this file has CRLF line endings.
+#
+Content-Length: 125
+
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
+#
+Content-Length: 180
+
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///foo.c","languageId":"c","version":1,"text":"int main(int i, char **a) { if (i = 2) {}}"}}}
+#
+# CHECK: {"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///foo.c","diagnostics":[{"range":{"start": {"line": 0, "character": 35}, "end": {"line": 0, "character": 35}},"severity":2,"message":"using the result of an assignment as a condition without parentheses"},{"range":{"start": {"line": 0, "character": 35}, "end": {"line": 0, "character": 35}},"severity":3,"message":"place parentheses around the assignment to silence this warning"},{"range":{"start": {"line": 0, "character": 35}, "end": {"line": 0, "character": 35}},"severity":3,"message":"use '==' to turn this assignment into an equality comparison"}]}}
+#
+Content-Length: 746
+
+ {"jsonrpc":"2.0","id":2,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///foo.c"},"range":{"start":{"line":104,"character":13},"end":{"line":0,"character":35}},"context":{"diagnostics":[{"range":{"start": {"line": 0, "character": 35}, "end": {"line": 0, "character": 35}},"severity":2,"message":"using the result of an assignment as a condition without parentheses"},{"range":{"start": {"line": 0, "character": 35}, "end": {"line": 0, "character": 35}},"severity":3,"message":"place parentheses around the assignment to silence this warning"},{"range":{"start": {"line": 0, "character": 35}, "end": {"line": 0, "character": 35}},"severity":3,"message":"use '==' to turn this assignment into an equality comparison"}]}}}
+#
+# CHECK: {"jsonrpc":"2.0","id":2, "result": [{"title":"Apply FixIt 'place parentheses around the assignment to silence this warning'", "command": "clangd.applyFix", "arguments": ["file:///foo.c", [{"range": {"start": {"line": 0, "character": 32}, "end": {"line": 0, "character": 32}}, "newText": "("},{"range": {"start": {"line": 0, "character": 37}, "end": {"line": 0, "character": 37}}, "newText": ")"}]]},{"title":"Apply FixIt 'use '==' to turn this assignment into an equality comparison'", "command": "clangd.applyFix", "arguments": ["file:///foo.c", [{"range": {"start": {"line": 0, "character": 34}, "end": {"line": 0, "character": 35}}, "newText": "=="}]]}]
+#
+Content-Length: 44
+
+{"jsonrpc":"2.0","id":3,"method":"shutdown"}
diff --git a/clang-tools-extra/test/clangd/formatting.test b/clang-tools-extra/test/clangd/formatting.test
@@ -4,12 +4,13 @@
 Content-Length: 125
 
 {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
-# CHECK: Content-Length: 294
+# CHECK: Content-Length: 332
 # CHECK: {"jsonrpc":"2.0","id":0,"result":{"capabilities":{
 # CHECK:   "textDocumentSync": 1,
 # CHECK:   "documentFormattingProvider": true,
 # CHECK:   "documentRangeFormattingProvider": true,
-# CHECK:   "documentOnTypeFormattingProvider": {"firstTriggerCharacter":"}","moreTriggerCharacter":[]}
+# CHECK:   "documentOnTypeFormattingProvider": {"firstTriggerCharacter":"}","moreTriggerCharacter":[]},
+# CHECK:   "codeActionProvider": true
 # CHECK: }}}
 #
 Content-Length: 193