[clang] [C++20][Modules] Implement P1857R3 Modules Dependency Discovery (PR #107168)

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git-clang-format --diff 448d8fa880be5cae0f63c3b248f07f647013a5a4 b7b4e2549a5fb723b455768f2bcf75bfab6cab04 --extensions h,cpp -- clang/include/clang/Basic/IdentifierTable.h clang/include/clang/Lex/Lexer.h clang/include/clang/Lex/Preprocessor.h clang/include/clang/Lex/Token.h clang/include/clang/Lex/TokenLexer.h clang/include/clang/Parse/Parser.h clang/lib/Basic/IdentifierTable.cpp clang/lib/Lex/DependencyDirectivesScanner.cpp clang/lib/Lex/Lexer.cpp clang/lib/Lex/PPDirectives.cpp clang/lib/Lex/PPMacroExpansion.cpp clang/lib/Lex/Preprocessor.cpp clang/lib/Lex/TokenLexer.cpp clang/lib/Parse/Parser.cpp clang/unittests/Lex/DependencyDirectivesScannerTest.cpp
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View the diff from clang-format here.
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``````````diff
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index a9acde7ac5..d8b0d4a540 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -400,7 +400,7 @@ private:
 
   /// Whether the last token we lexed was an '@'.
   bool LastTokenWasAt = false;
-  
+
   struct ExportContextualKeywordInfo {
     Token ExportTok;
     bool TokAtPhysicalStartOfLine;
@@ -1847,7 +1847,8 @@ public:
   /// This consumes the import, module directive, modifies the
   /// lexer/preprocessor state, and advances the lexer(s) so that the next token
   /// read is the correct one.
-  bool HandleModuleContextualKeyword(Token &Result, bool TokAtPhysicalStartOfLine);
+  bool HandleModuleContextualKeyword(Token &Result,
+                                     bool TokAtPhysicalStartOfLine);
 
   void HandleModuleDirective(Token &ModuleOrImportKeyword);
   void LexAfterModuleImport(SmallVectorImpl<Token> &Suffix, bool IsImport);
diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
index 10ed86d5d5..d44f553e59 100644
--- a/clang/lib/Basic/IdentifierTable.cpp
+++ b/clang/lib/Basic/IdentifierTable.cpp
@@ -457,7 +457,7 @@ tok::PPKeywordKind IdentifierInfo::getPPKeywordID() const {
   CASE( 6, 'd', 'f', define);
   CASE( 6, 'i', 'n', ifndef);
   CASE( 6, 'i', 'p', import);
-  CASE( 6, 'm', 'd', module);
+  CASE(6, 'm', 'd', module);
   CASE( 6, 'p', 'a', pragma);
 
   CASE( 7, 'd', 'f', defined);
diff --git a/clang/lib/Lex/DependencyDirectivesScanner.cpp b/clang/lib/Lex/DependencyDirectivesScanner.cpp
index 58e92977f9..245ce25b82 100644
--- a/clang/lib/Lex/DependencyDirectivesScanner.cpp
+++ b/clang/lib/Lex/DependencyDirectivesScanner.cpp
@@ -857,7 +857,8 @@ bool Scanner::lexPPLine(const char *&First, const char *const End) {
   if (*First == '@')
     return lexAt(First, End);
 
-  // if (!LangOpts.CPlusPlusModules && (*First == 'i' || *First == 'e' || *First == 'm'))
+  // if (!LangOpts.CPlusPlusModules && (*First == 'i' || *First == 'e' || *First
+  // == 'm'))
   //   return lexModule(First, End);
 
   if (*First == '_') {
@@ -871,7 +872,7 @@ bool Scanner::lexPPLine(const char *&First, const char *const End) {
   TheLexer.setParsingPreprocessorDirective(true);
   auto ScEx2 = make_scope_exit(
       [&]() { TheLexer.setParsingPreprocessorDirective(false); });
-   if (*First == 'i' || *First == 'e' || *First == 'm')
+  if (*First == 'i' || *First == 'e' || *First == 'm')
     return lexModule(First, End);
   // Lex '#'.
   const dependency_directives_scan::Token &HashTok = lexToken(First, End);
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index b40de9d918..7cce869662 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -4023,12 +4023,13 @@ void Preprocessor::HandleEmbedDirective(SourceLocation HashLoc, Token &EmbedTok,
   HandleEmbedDirectiveImpl(HashLoc, *Params, BinaryContents);
 }
 
-void Preprocessor::LexAfterModuleImport(SmallVectorImpl<Token> &Suffix, bool IsImport) {
+void Preprocessor::LexAfterModuleImport(SmallVectorImpl<Token> &Suffix,
+                                        bool IsImport) {
   Token Result;
   Suffix.clear();
 Retry:
   if (IsImport && getLangOpts().CPlusPlusModules) {
-    (void) LexHeaderName(Result);
+    (void)LexHeaderName(Result);
     if (Result.is(tok::colon) && ModuleDeclState.isNamedModule()) {
       std::string Name = ModuleDeclState.getPrimaryName().str();
       Name += ":";
@@ -4172,8 +4173,7 @@ Retry:
   // We don't/shouldn't load the standard c++20 modules when preprocessing.
   if (getLangOpts().Modules && !isInImportingCXXNamedModules()) {
     Imported = TheModuleLoader.loadModule(ModuleImportLoc,
-                                          NamedModuleImportPath,
-                                          Module::Hidden,
+                                          NamedModuleImportPath, Module::Hidden,
                                           /*IsInclusionDirective=*/false);
     if (Imported)
       makeModuleVisible(Imported, SemiLoc);
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index eb694ce415..a4ac1505be 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -1154,7 +1154,8 @@ bool Preprocessor::HandleModuleContextualKeyword(
   } else if (!TokAtPhysicalStartOfLine)
     return false;
 
-  bool SavedParsingPreprocessorDirective = CurPPLexer->ParsingPreprocessorDirective;
+  bool SavedParsingPreprocessorDirective =
+      CurPPLexer->ParsingPreprocessorDirective;
   CurPPLexer->ParsingPreprocessorDirective = true;
   // Peek next token.
   auto NextTok = peekNextPPToken().value_or(Token{});

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https://github.com/llvm/llvm-project/pull/107168