4 files changed, 46 insertions, 1 deletions
diff --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
index 2989c760b67..a5daf8aed46 100644
--- a/clang/lib/Format/FormatToken.h
+++ b/clang/lib/Format/FormatToken.h
@@ -60,6 +60,7 @@ namespace format {
   TYPE(JsExponentiationEqual)                                                  \
   TYPE(JsFatArrow)                                                             \
   TYPE(JsNonNullAssertion)                                                     \
+  TYPE(JsPrivateIdentifier)                                                    \
   TYPE(JsTypeColon)                                                            \
   TYPE(JsTypeOperator)                                                         \
   TYPE(JsTypeOptionalQuestion)                                                 \
diff --git a/clang/lib/Format/FormatTokenLexer.cpp b/clang/lib/Format/FormatTokenLexer.cpp
index 2f1b08a8b06..da755e36c15 100644
--- a/clang/lib/Format/FormatTokenLexer.cpp
+++ b/clang/lib/Format/FormatTokenLexer.cpp
@@ -95,6 +95,8 @@ void FormatTokenLexer::tryMergePreviousTokens() {
       Tokens.back()->Tok.setKind(tok::starequal);
       return;
     }
+    if (tryMergeJSPrivateIdentifier())
+      return;
   }
 
   if (Style.Language == FormatStyle::LK_Java) {
@@ -121,6 +123,25 @@ bool FormatTokenLexer::tryMergeNSStringLiteral() {
   return true;
 }
 
+bool FormatTokenLexer::tryMergeJSPrivateIdentifier() {
+  // Merges #idenfier into a single identifier with the text #identifier
+  // but the token tok::identifier.
+  if (Tokens.size() < 2)
+    return false;
+  auto &Hash = *(Tokens.end() - 2);
+  auto &Identifier = *(Tokens.end() - 1);
+  if (!Hash->is(tok::hash) || !Identifier->is(tok::identifier))
+    return false;
+  Hash->Tok.setKind(tok::identifier);
+  Hash->TokenText =
+      StringRef(Hash->TokenText.begin(),
+                Identifier->TokenText.end() - Hash->TokenText.begin());
+  Hash->ColumnWidth += Identifier->ColumnWidth;
+  Hash->Type = TT_JsPrivateIdentifier;
+  Tokens.erase(Tokens.end() - 1);
+  return true;
+}
+
 bool FormatTokenLexer::tryMergeLessLess() {
   // Merge X,less,less,Y into X,lessless,Y unless X or Y is less.
   if (Tokens.size() < 3)
diff --git a/clang/lib/Format/FormatTokenLexer.h b/clang/lib/Format/FormatTokenLexer.h
index 61a4c041d1e..a9646261461 100644
--- a/clang/lib/Format/FormatTokenLexer.h
+++ b/clang/lib/Format/FormatTokenLexer.h
@@ -48,6 +48,7 @@ private:
 
   bool tryMergeLessLess();
   bool tryMergeNSStringLiteral();
+  bool tryMergeJSPrivateIdentifier();
 
   bool tryMergeTokens(ArrayRef<tok::TokenKind> Kinds, TokenType NewType);
 
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index 528e4cf57cb..b332f1bd975 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -2334,5 +2334,27 @@ TEST_F(FormatTestJS, ConditionalTypes) {
       "                     never) extends((k: infer I) => void) ? I : never;");
 }
 
-} // end namespace tooling
+TEST_F(FormatTestJS, SupportPrivateFieldsAndMethods) {
+  verifyFormat("class Example {\n"
+               "  pub = 1;\n"
+               "  #priv = 2;\n"
+               "  static pub2 = 'foo';\n"
+               "  static #priv2 = 'bar';\n"
+               "  method() {\n"
+               "    this.#priv = 5;\n"
+               "  }\n"
+               "  static staticMethod() {\n"
+               "    switch (this.#priv) {\n"
+               "      case '1':\n"
+               "        #priv = 3;\n"
+               "        break;\n"
+               "    }\n"
+               "  }\n"
+               "  #privateMethod() {\n"
+               "    this.#privateMethod();  // infinite loop\n"
+               "  }\n"
+               "  static #staticPrivateMethod() {}\n");
+}
+
+} // namespace format
 } // end namespace clang