Parsing:Allow QuestionToken as start of type

src/compiler/parser.ts

@@ -2721,6 +2721,7 @@ namespace ts {
                 case SyntaxKind.FalseKeyword:
                 case SyntaxKind.ObjectKeyword:
                 case SyntaxKind.AsteriskToken:
+                case SyntaxKind.QuestionToken:
                     return true;
                 case SyntaxKind.MinusToken:
                     return lookAhead(nextTokenIsNumericLiteral);