clang-format: [JS] handle parenthesized class expressions.

[mprobst]

Summary

In JavaScript, classes are expressions, so they can appear e.g. in
argument lists.

var C = foo(class {
  bar() {
    return 1;
  }
};

[djasper]

Thanks

[mprobst]

• Parse nested classes as child expressions.

[djasper]

Sorry.. Should have caught this in the initial review. Still looks good.

lib/Format/UnwrappedLineParser.cpp

case tok::l_brace:
       if (!tryToParseBracedList())
         parseChildBlock();
       break;
     case tok::at:
       nextToken();
       if (FormatTok->Tok.is(tok::l_brace))
         parseBracedList();
       break;
+    case tok::kw_class:
+      if (Style.Language == FormatStyle::LK_JavaScript) {
+        parseRecord();
+        addUnwrappedLine();
+      } else {
+        nextToken();
+      }
+      break;
     case tok::identifier:
       if (Style.Language == FormatStyle::LK_JavaScript &&
           (FormatTok->is(Keywords.kw_function) ||
            FormatTok->startsSequence(Keywords.kw_async, Keywords.kw_function)))
         tryToParseJSFunction();
       else
         nextToken();
       break;

unittests/Format/FormatTestJS.cpp

TEST_F(FormatTestJS, ClassDeclarations) {
   verifyFormat("class C {\n  x: string = 12;\n}");
   verifyFormat("class C {\n  x(): string => 12;\n}");
   verifyFormat("class C {\n  ['x' + 2]: string = 12;\n}");
   verifyFormat("class C {\n  private x: string = 12;\n}");
   verifyFormat("class C {\n  private static x: string = 12;\n}");
   verifyFormat("class C {\n  static x(): string {\n    return 'asd';\n  }\n}");
   verifyFormat("class C extends P implements I {}");
   verifyFormat("class C extends p.P implements i.I {}");
+  verifyFormat(
+      "x(class {\n"
+      "  a(): A {}\n"
+      "});");
   verifyFormat("class Test {\n"
                "  aaaaaaaaaaaaaaaa(aaaaaaaaaaaaaaa: aaaaaaaaaaaaaaaaaaaa):\n"
                "      aaaaaaaaaaaaaaaaaaaaaa {}\n"
                "}");
   verifyFormat("foo = class Name {\n"
                "  constructor() {}\n"
                "};");
   verifyFormat("foo = class {\n"