Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -2225,6 +2225,12 @@
   } else if (Style.Language == FormatStyle::LK_JavaScript) {
     if (Left.is(TT_JsFatArrow))
       return true;
+    if (Left.is(Keywords.kw_async) && Right.is(tok::l_paren) &&
+        Right.MatchingParen && Right.MatchingParen->getNextNonComment() &&
+        Right.MatchingParen->getNextNonComment()->is(TT_JsFatArrow))
+      // An async arrow function, for example: `x = async () => foo();`,
+      // as opposed to calling a function called async: `x = async();`
+      return true;
     if ((Left.is(TT_TemplateString) && Left.TokenText.endswith("${")) ||
         (Right.is(TT_TemplateString) && Right.TokenText.startswith("}")))
       return false;
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -463,6 +463,8 @@
   verifyFormat("export async function f() {\n"
                "  return fetch(x);\n"
                "}");
+  verifyFormat("let x = async () => f();");
+  verifyFormat("let x = async();");
   verifyFormat("class X {\n"
                "  async asyncMethod() {\n"
                "    return fetch(1);\n"