Reinstate the syntax tree test for 'static' in an array subscript

clang/unittests/Tooling/Syntax/TreeTest.cpp

static llvm::ArrayRef<syntax::Token> tokens(syntax::Node *N) {
   return llvm::makeArrayRef(T->firstLeaf()->token(),
                             T->lastLeaf()->token() + 1);
 }
 
 struct TestClangConfig {
   TestLanguage Language;
   std::string Target;
 
+  bool isC99OrLater() const { return Language == Lang_C99; }
+
   bool isCXX() const {
     return Language == Lang_CXX03 || Language == Lang_CXX11 ||
            Language == Lang_CXX14 || Language == Lang_CXX17 ||
            Language == Lang_CXX20;
   }
 
   bool isCXX11OrLater() const {
     return Language == Lang_CXX11 || Language == Lang_CXX14 ||

 }
 
 TEST_P(SyntaxTreeTest, ArraySubscriptsInDeclarators) {
   expectTreeDumpEqual(
       R"cpp(
 int a[10];
 int b[1][2][3];
 int c[] = {1,2,3};
-// void f(int xs[static 10]);
     )cpp",
       R"txt(
 *: TranslationUnit
 |-SimpleDeclaration
 | |-int
 | |-SimpleDeclarator
 | | |-a
 | | `-ArraySubscript
`-SimpleDeclaration
   |     | `-2
   |     |-,
   |     |-UnknownExpression
   |     | `-3
   |     `-}
   `-;       )txt");
 }
 
+TEST_P(SyntaxTreeTest, StaticArraySubscriptsInDeclarators) {
+  if (!GetParam().isC99OrLater()) {
+    return;
+  }
+  expectTreeDumpEqual(
+      R"cpp(
+void f(int xs[static 10]);
+    )cpp",
+      R"txt(
+*: TranslationUnit
+`-SimpleDeclaration
+  |-void
+  |-SimpleDeclarator
+  | |-f
+  | `-ParametersAndQualifiers
+  |   |-(
+  |   |-SimpleDeclaration
+  |   | |-int
+  |   | `-SimpleDeclarator
+  |   |   |-xs
+  |   |   `-ArraySubscript
+  |   |     |-[
+  |   |     |-static
+  |   |     |-UnknownExpression
+  |   |     | `-10
+  |   |     `-]
+  |   `-)
+  `-;       )txt");
+}
+
 TEST_P(SyntaxTreeTest, ParameterListsInDeclarators) {
   if (!GetParam().isCXX()) {
     // TODO: Split parts that depend on C++ into a separate test.
     return;
   }
   expectTreeDumpEqual(
       R"cpp(
 struct Test {