clang-format: [JS] Support pseudo-keywords.

[mprobst]

Summary

JavaScript allows keywords to appear in IdenfierName positions, e.g. fields, or
object literal members, but not as plain identifiers.

[djasper]

Looks good.

[djasper]

Submitted as r248714.

lib/Format/TokenAnnotator.cpp

if (CurrentToken) {
         }
         if (CurrentToken->isOneOf(tok::r_paren, tok::r_square))
           return false;
         updateParameterCount(Left, CurrentToken);
         if (CurrentToken->isOneOf(tok::colon, tok::l_brace)) {
           FormatToken *Previous = CurrentToken->getPreviousNonComment();
           if ((CurrentToken->is(tok::colon) ||
                Style.Language == FormatStyle::LK_Proto) &&
-              Previous->is(tok::identifier))
+              Previous->Tok.getIdentifierInfo())
             Previous->Type = TT_SelectorName;
           if (CurrentToken->is(tok::colon) ||
               Style.Language == FormatStyle::LK_JavaScript)
             Left->Type = TT_DictLiteral;
         }
         if (!consumeToken())
           return false;
       }

lib/Format/UnwrappedLineParser.cpp

case tok::kw_class:
       }
       break;
     case tok::period:
       nextToken();
       // In Java, classes have an implicit static member "class".
       if (Style.Language == FormatStyle::LK_Java && FormatTok &&
           FormatTok->is(tok::kw_class))
         nextToken();
+      if (Style.Language == FormatStyle::LK_JavaScript && FormatTok &&
+          FormatTok->Tok.getIdentifierInfo())
+        // JavaScript only has pseudo keywords, all keywords are allowed to
+        // appear in "IdentifierName" positions. See http://es5.github.io/#x7.6
+        nextToken();
       break;
     case tok::semi:
       nextToken();
       addUnwrappedLine();
       return;
     case tok::r_brace:
       addUnwrappedLine();
       return;

unittests/Format/FormatTestJS.cpp

 TEST_F(FormatTestJS, UnderstandsAmpAmp) {
   verifyFormat("e && e.SomeFunction();");
 }
 
 TEST_F(FormatTestJS, LiteralOperatorsCanBeKeywords) {
   verifyFormat("not.and.or.not_eq = 1;");
 }
 
+TEST_F(FormatTestJS, ReservedWords) {
+  // JavaScript reserved words (aka keywords) are only illegal when used as
+  // Identifiers, but are legal as IdentifierNames.
+  verifyFormat("x.class.struct = 1;");
+  verifyFormat("x.case = 1;");
+  verifyFormat("x.interface = 1;");
+  verifyFormat("x = {\n"
+               "  a: 12,\n"
+               "  interface: 1,\n"
+               "  switch: 1,\n"
+               "};");
+}
+
 TEST_F(FormatTestJS, ES6DestructuringAssignment) {
   verifyFormat("var [a, b, c] = [1, 2, 3];");
   verifyFormat("var {a, b} = {a: 1, b: 2};");
 }
 
 TEST_F(FormatTestJS, ContainerLiterals) {
   verifyFormat("var x = {y: function(a) { return a; }};");
   verifyFormat("return {\n"