Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -2341,7 +2341,8 @@
         Left.isOneOf(Keywords.kw_function, Keywords.kw_yield))
       return false;
     if (Right.isOneOf(tok::l_brace, tok::l_square) &&
-        Left.isOneOf(Keywords.kw_function, Keywords.kw_yield))
+        Left.isOneOf(Keywords.kw_function, Keywords.kw_yield,
+                     Keywords.kw_extends, Keywords.kw_implements))
       return true;
     // JS methods can use some keywords as names (e.g. `delete()`).
     if (Right.is(tok::l_paren) && Line.MustBeDeclaration &&
Index: lib/Format/UnwrappedLineParser.cpp
===================================================================
--- lib/Format/UnwrappedLineParser.cpp
+++ lib/Format/UnwrappedLineParser.cpp
@@ -1970,6 +1970,17 @@
          ((Style.Language == FormatStyle::LK_Java ||
            Style.Language == FormatStyle::LK_JavaScript) &&
           FormatTok->isOneOf(tok::period, tok::comma))) {
+    if (Style.Language == FormatStyle::LK_JavaScript &&
+        FormatTok->isOneOf(Keywords.kw_extends, Keywords.kw_implements)) {
+      // JavaScript/TypeScript supports inline object types in
+      // extends/implements positions:
+      //     class Foo implements {bar: number} { }
+      nextToken();
+      if (FormatTok->is(tok::l_brace)) {
+        tryToParseBracedList();
+        continue;
+      }
+    }
     bool IsNonMacroIdentifier =
         FormatTok->is(tok::identifier) &&
         FormatTok->TokenText != FormatTok->TokenText.upper();
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -1400,6 +1400,17 @@
                "}");
 }
 
+TEST_F(FormatTestJS, ObjectTypesInExtendsImplements) {
+  verifyFormat("class C extends {} {}");
+  verifyFormat("class C implements {bar: number} {}");
+  // Somewhat odd, but probably closest to reasonable formatting?
+  verifyFormat("class C implements {\n"
+               "  bar: number,\n"
+               "  baz: string,\n"
+               "} {}");
+  verifyFormat("class C<P extends {}> {}");
+}
+
 TEST_F(FormatTestJS, EnumDeclarations) {
   verifyFormat("enum Foo {\n"
                "  A = 1,\n"