[clang-format] Fix wrong indentation of namespace identifiers after a concept declaration.

[curdeius]

Summary

Before this patch, the code:

template <class T>
concept a_concept = X<>;
namespace B {
struct b_struct {};
} // namespace B

with config:

NamespaceIndentation: None

was wrongly indented inside namespace B, giving:

template <class T>
concept a_concept = X<>;
namespace B {
  struct b_struct {};
} // namespace B

Fixes https://github.com/llvm/llvm-project/issues/50645

[curdeius]

Undo unrelated changes.

[MyDeveloperDay]

LGTM

clang/lib/Format/UnwrappedLineParser.cpp

case tok::at:
         parseTryCatch();
         return;
       default:
         break;
       }
       break;
     case tok::kw_concept:
       parseConcept();
-      break;
+      return;
     case tok::kw_requires:
       parseRequires();
       break;
     case tok::kw_enum:
       // Ignore if this is part of "template <enum ...".
       if (Previous && Previous->is(tok::less)) {
         nextToken();
         break;

clang/unittests/Format/FormatTest.cpp

EXPECT_EQ("namespace out {\n"
             "} // namespace out",
             format("namespace out {\n"
                    "int i;\n"
                    "namespace in {\n"
                    "int i;\n"
                    "} // namespace in\n"
                    "} // namespace out",
                    Style));
+
+  Style.NamespaceIndentation = FormatStyle::NI_None;
+  verifyFormat("template <class T>\n"
+               "concept a_concept = X<>;\n"
+               "namespace B {\n"
+               "struct b_struct {};\n"
+               "} // namespace B\n",
+               Style);
 }
 
 TEST_F(FormatTest, NamespaceMacros) {
   FormatStyle Style = getLLVMStyle();
   Style.NamespaceMacros.push_back("TESTSUITE");
 
   verifyFormat("TESTSUITE(A) {\n"
                "int foo();\n"