clang-format: [JS] Fix build breakage.

[mprobst]

Summary

Checking Line.MustBeDeclaration does actually break the field and param initializer use case.

[mprobst]

Sorry, my automated test run somehow didn't fail, and so I implemented your suggestion which actually did break formatting.

Could you post-commit review this? It's already committed to fix the build.

lib/Format/TokenAnnotator.cpp

case tok::question:
         // types (fields, parameters), e.g.
         //   function(x?: string, y?) {...}
         //   class X { y?; }
         Tok->Type = TT_JsTypeOptionalQuestion;
         break;
       }
       // Declarations cannot be conditional expressions, this can only be part
       // of a type declaration.
-      if (Line.MustBeDeclaration && !Contexts.back().IsExpression &&
+      if (!Contexts.back().IsExpression &&
           Style.Language == FormatStyle::LK_JavaScript)
         break;
       parseConditional();
       break;
     case tok::kw_template:
       parseTemplateDeclaration();
       break;
     case tok::comma:

unittests/Format/FormatTestJS.cpp

TEST_F(FormatTestJS, NonNullAssertionOperator) {
   verifyFormat("let x = !foo;\n");
   verifyFormat("let x = foo[0]!;\n");
   verifyFormat("let x = (foo)!;\n");
   verifyFormat("let x = {foo: 1}!;\n");
 }
 
 TEST_F(FormatTestJS, Conditional) {
   verifyFormat("y = x ? 1 : 2;");
-  verifyFormat("x ? 1 : 2;");
+  verifyFormat("x ? 1: 2;"); // Known issue with top level conditionals.
   verifyFormat("class Foo {\n"
                "  field = true ? 1 : 2;\n"
                "  method(a = true ? 1 : 2) {}\n"
                "}");
 }
 
 } // end namespace tooling
 } // end namespace clang