[clang][serialization] Pass ASTContext explicitly (llvm#115235)

This patch removes `ASTWriter::Context` and starts passing `ASTContext
&` explicitly to functions that actually need it. This is a
non-functional change with the end-goal of being able to write
lightweight PCM files with no `ASTContext` at all.

(cherry picked from commit 53e49f1)

Author: jansvoboda11

clang/include/clang/Serialization/ASTRecordWriter.h

@@ -60,8 +60,9 @@ class ASTRecordWriter
 
 public:
   /// Construct a ASTRecordWriter that uses the default encoding scheme.
-  ASTRecordWriter(ASTWriter &W, ASTWriter::RecordDataImpl &Record)
-      : DataStreamBasicWriter(W.getASTContext()), Writer(&W), Record(&Record) {}
+  ASTRecordWriter(ASTContext &Context, ASTWriter &W,
+                  ASTWriter::RecordDataImpl &Record)
+      : DataStreamBasicWriter(Context), Writer(&W), Record(&Record) {}
 
   /// Construct a ASTRecordWriter that uses the same encoding scheme as another
   /// ASTRecordWriter.
@@ -208,7 +209,7 @@ class ASTRecordWriter
 
   /// Emit a reference to a type.
   void AddTypeRef(QualType T) {
-    return Writer->AddTypeRef(T, *Record);
+    return Writer->AddTypeRef(getASTContext(), T, *Record);
   }
   void writeQualType(QualType T) {
     AddTypeRef(T);

clang/include/clang/Serialization/ASTWriter.h

@@ -119,9 +119,6 @@ class ASTWriter : public ASTDeserializationListener,
   /// The PCM manager which manages memory buffers for pcm files.
   InMemoryModuleCache &ModuleCache;
 
-  /// The ASTContext we're writing.
-  ASTContext *Context = nullptr;
-
   /// The preprocessor we're writing.
   Preprocessor *PP = nullptr;
 
@@ -537,10 +534,11 @@ class ASTWriter : public ASTDeserializationListener,
   unsigned getSubmoduleID(Module *Mod);
 
   /// Write the given subexpression to the bitstream.
-  void WriteSubStmt(Stmt *S);
+  void WriteSubStmt(ASTContext &Context, Stmt *S);
 
   void WriteBlockInfoBlock();
-  void WriteControlBlock(Preprocessor &PP, StringRef isysroot);
+  void WriteControlBlock(ASTContext &Context, Preprocessor &PP,
+                         StringRef isysroot);
 
   /// Write out the signature and diagnostic options, and return the signature.
   void writeUnhashedControlBlock(Preprocessor &PP);
@@ -556,34 +554,36 @@ class ASTWriter : public ASTDeserializationListener,
   void WriteHeaderSearch(const HeaderSearch &HS);
   void WritePreprocessorDetail(PreprocessingRecord &PPRec,
                                uint64_t MacroOffsetsBase);
-  void WriteSubmodules(Module *WritingModule);
+  void WriteSubmodules(Module *WritingModule, ASTContext &Context);
 
   void WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag,
                                      bool isModule);
 
   unsigned TypeExtQualAbbrev = 0;
   void WriteTypeAbbrevs();
-  void WriteType(QualType T);
+  void WriteType(ASTContext &Context, QualType T);
 
   bool isLookupResultExternal(StoredDeclsList &Result, DeclContext *DC);
 
-  void GenerateNameLookupTable(const DeclContext *DC,
+  void GenerateNameLookupTable(ASTContext &Context, const DeclContext *DC,
                                llvm::SmallVectorImpl<char> &LookupTable);
   uint64_t WriteDeclContextLexicalBlock(ASTContext &Context,
                                         const DeclContext *DC);
   uint64_t WriteDeclContextVisibleBlock(ASTContext &Context, DeclContext *DC);
   void WriteTypeDeclOffsets();
   void WriteFileDeclIDsMap();
-  void WriteComments();
+  void WriteComments(ASTContext &Context);
   void WriteSelectors(Sema &SemaRef);
   void WriteReferencedSelectorsPool(Sema &SemaRef);
   void WriteIdentifierTable(Preprocessor &PP, IdentifierResolver &IdResolver,
                             bool IsModule);
   void WriteDeclAndTypes(ASTContext &Context);
   void PrepareWritingSpecialDecls(Sema &SemaRef);
   void WriteSpecialDeclRecords(Sema &SemaRef);
-  void WriteDeclUpdatesBlocks(RecordDataImpl &OffsetsRecord);
-  void WriteDeclContextVisibleUpdate(const DeclContext *DC);
+  void WriteDeclUpdatesBlocks(ASTContext &Context,
+                              RecordDataImpl &OffsetsRecord);
+  void WriteDeclContextVisibleUpdate(ASTContext &Context,
+                                     const DeclContext *DC);
   void WriteFPPragmaOptions(const FPOptionsOverride &Opts);
   void WriteOpenCLExtensions(Sema &SemaRef);
   void WriteCUDAPragmas(Sema &SemaRef);
@@ -645,11 +645,6 @@ class ASTWriter : public ASTDeserializationListener,
             bool GeneratingReducedBMI = false);
   ~ASTWriter() override;
 
-  ASTContext &getASTContext() const {
-    assert(Context && "requested AST context when not writing AST");
-    return *Context;
-  }
-
   const LangOptions &getLangOpts() const;
 
   /// Get a timestamp for output into the AST file. The actual timestamp
@@ -715,10 +710,10 @@ class ASTWriter : public ASTDeserializationListener,
   uint32_t getMacroDirectivesOffset(const IdentifierInfo *Name);
 
   /// Emit a reference to a type.
-  void AddTypeRef(QualType T, RecordDataImpl &Record);
+  void AddTypeRef(ASTContext &Context, QualType T, RecordDataImpl &Record);
 
   /// Force a type to be emitted and get its ID.
-  serialization::TypeID GetOrCreateTypeID(QualType T);
+  serialization::TypeID GetOrCreateTypeID(ASTContext &Context, QualType T);
 
   /// Find the first local declaration of a given local redeclarable
   /// decl.