[Modules] Fix ModuleDeclState transition when module is used as a regular identifier (#71134)

`ModuleDeclState` is incorrectly changed to `NamedModuleImplementation`
for `struct module {}; void foo(module a);`. This is mostly benign but
leads to a spurious warning after #69555.

A real world example is:
```
// pybind11.h
class module_ { ... };
using module = module_;

// tensorflow
void DefineMetricsModule(pybind11::module main_module);
// `module main_module);` incorrectly changes `ModuleDeclState` to `NamedModuleImplementation`

#include <algorithm> // spurious warning
```

1 files changed, 21 insertions, 18 deletions

diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index ede4c51..45c0f84 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -957,26 +957,29 @@ void Preprocessor::Lex(Token &Result) {
       ModuleDeclState.handlePeriod();
       break;
     case tok::identifier:
-      if (Result.getIdentifierInfo()->isModulesImport()) {
-        TrackGMFState.handleImport(StdCXXImportSeqState.afterTopLevelSeq());
-        StdCXXImportSeqState.handleImport();
-        if (StdCXXImportSeqState.afterImportSeq()) {
-          ModuleImportLoc = Result.getLocation();
-          NamedModuleImportPath.clear();
-          IsAtImport = false;
-          ModuleImportExpectsIdentifier = true;
-          CurLexerKind = CLK_LexAfterModuleImport;
-        }
-        break;
-      } else if (Result.getIdentifierInfo() == getIdentifierInfo("module")) {
-        TrackGMFState.handleModule(StdCXXImportSeqState.afterTopLevelSeq());
-        ModuleDeclState.handleModule();
-        break;
-      } else {
-        ModuleDeclState.handleIdentifier(Result.getIdentifierInfo());
-        if (ModuleDeclState.isModuleCandidate())
+      // Check "import" and "module" when there is no open bracket. The two
+      // identifiers are not meaningful with open brackets.
+      if (StdCXXImportSeqState.atTopLevel()) {
+        if (Result.getIdentifierInfo()->isModulesImport()) {
+          TrackGMFState.handleImport(StdCXXImportSeqState.afterTopLevelSeq());
+          StdCXXImportSeqState.handleImport();
+          if (StdCXXImportSeqState.afterImportSeq()) {
+            ModuleImportLoc = Result.getLocation();
+            NamedModuleImportPath.clear();
+            IsAtImport = false;
+            ModuleImportExpectsIdentifier = true;
+            CurLexerKind = CLK_LexAfterModuleImport;
+          }
           break;
+        } else if (Result.getIdentifierInfo() == getIdentifierInfo("module")) {
+          TrackGMFState.handleModule(StdCXXImportSeqState.afterTopLevelSeq());
+          ModuleDeclState.handleModule();
+          break;
+        }
       }
+      ModuleDeclState.handleIdentifier(Result.getIdentifierInfo());
+      if (ModuleDeclState.isModuleCandidate())
+        break;
       [[fallthrough]];
     default:
       TrackGMFState.handleMisc();