[clang][NFC] Clean up Sema headers

When various `Sema*.h` and `Sema*.cpp` files were created, cleanup of
`Sema.h` includes and forward declarations was left for the later.
Now's the time. This commit touches `Sema.h` and Sema components:
1. Unused includes are removed.
2. Unused forward declarations are removed.
3. Missing includes are added (those files are largely IWYU-clean now).
4. Includes were converted into forward declarations where possible.

As this commit focuses on headers, all changes to `.cpp` files were
minimal, and were aiming at keeping everything buildable.

Author: Endilll

clang/include/clang/AST/Attr.h

@@ -372,7 +372,7 @@ class ParamIdx {
 static_assert(sizeof(ParamIdx) == sizeof(ParamIdx::SerialType),
               "ParamIdx does not fit its serialization type");
 
-#include "clang/AST/Attrs.inc"
+#include "clang/AST/Attrs.inc" // IWYU pragma: export
 
 inline const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,
                                              const Attr *At) {

clang/include/clang/Sema/Sema.h

@@ -15,161 +15,143 @@
 #define LLVM_CLANG_SEMA_SEMA_H
 
 #include "clang/APINotes/APINotesManager.h"
-#include "clang/AST/ASTConcept.h"
 #include "clang/AST/ASTFwd.h"
 #include "clang/AST/Attr.h"
-#include "clang/AST/Availability.h"
-#include "clang/AST/ComparisonCategories.h"
+#include "clang/AST/AttrIterator.h"
+#include "clang/AST/CharUnits.h"
+#include "clang/AST/DeclBase.h"
+#include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/DeclarationName.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/ExprConcepts.h"
-#include "clang/AST/ExprObjC.h"
 #include "clang/AST/ExternalASTSource.h"
-#include "clang/AST/LocInfoType.h"
-#include "clang/AST/MangleNumberingContext.h"
-#include "clang/AST/NSAPI.h"
-#include "clang/AST/PrettyPrinter.h"
+#include "clang/AST/NestedNameSpecifier.h"
+#include "clang/AST/OperationKinds.h"
 #include "clang/AST/StmtCXX.h"
+#include "clang/AST/Type.h"
 #include "clang/AST/TypeLoc.h"
-#include "clang/AST/TypeOrdering.h"
-#include "clang/Basic/BitmaskEnum.h"
+#include "clang/Basic/AttrSubjectMatchRules.h"
 #include "clang/Basic/Builtins.h"
+#include "clang/Basic/CapturedStmt.h"
 #include "clang/Basic/Cuda.h"
-#include "clang/Basic/DarwinSDKInfo.h"
+#include "clang/Basic/DiagnosticSema.h"
+#include "clang/Basic/ExceptionSpecificationType.h"
 #include "clang/Basic/ExpressionTraits.h"
-#include "clang/Basic/IdentifierTable.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Basic/Lambda.h"
+#include "clang/Basic/LangOptions.h"
 #include "clang/Basic/Module.h"
 #include "clang/Basic/OpenCLOptions.h"
+#include "clang/Basic/OperatorKinds.h"
+#include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Basic/PragmaKinds.h"
+#include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/Specifiers.h"
 #include "clang/Basic/TemplateKinds.h"
+#include "clang/Basic/TokenKinds.h"
 #include "clang/Basic/TypeTraits.h"
 #include "clang/Sema/AnalysisBasedWarnings.h"
 #include "clang/Sema/Attr.h"
 #include "clang/Sema/CleanupInfo.h"
 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/ExternalSemaSource.h"
 #include "clang/Sema/IdentifierResolver.h"
-#include "clang/Sema/ObjCMethodList.h"
 #include "clang/Sema/Ownership.h"
+#include "clang/Sema/ParsedAttr.h"
 #include "clang/Sema/Redeclaration.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/SemaBase.h"
-#include "clang/Sema/SemaConcept.h"
-#include "clang/Sema/SemaDiagnostic.h"
 #include "clang/Sema/TypoCorrection.h"
 #include "clang/Sema/Weak.h"
+#include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/BitmaskEnum.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/FloatingPointMode.h"
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/STLForwardCompat.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/TinyPtrVector.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/ErrorHandling.h"
+#include <cassert>
+#include <climits>
+#include <cstddef>
+#include <cstdint>
 #include <deque>
+#include <functional>
+#include <iterator>
 #include <memory>
 #include <optional>
 #include <string>
 #include <tuple>
+#include <type_traits>
+#include <utility>
 #include <vector>
 
 namespace llvm {
-class APSInt;
-template <typename ValueT, typename ValueInfoT> class DenseSet;
-class SmallBitVector;
 struct InlineAsmIdentifierInfo;
 } // namespace llvm
 
 namespace clang {
 class ADLResult;
+class APValue;
+struct ASTConstraintSatisfaction;
 class ASTConsumer;
 class ASTContext;
+class ASTDeclReader;
 class ASTMutationListener;
 class ASTReader;
 class ASTWriter;
-class ArrayType;
-class ParsedAttr;
-class BindingDecl;
-class BlockDecl;
-class CapturedDecl;
 class CXXBasePath;
 class CXXBasePaths;
-class CXXBindTemporaryExpr;
-typedef SmallVector<CXXBaseSpecifier *, 4> CXXCastPath;
-class CXXConstructorDecl;
-class CXXConversionDecl;
-class CXXDeleteExpr;
-class CXXDestructorDecl;
 class CXXFieldCollector;
-class CXXMemberCallExpr;
-class CXXMethodDecl;
-class CXXScopeSpec;
-class CXXTemporary;
-class CXXTryStmt;
-class CallExpr;
-class ClassTemplateDecl;
-class ClassTemplatePartialSpecializationDecl;
-class ClassTemplateSpecializationDecl;
-class VarTemplatePartialSpecializationDecl;
 class CodeCompleteConsumer;
-class CodeCompletionAllocator;
-class CodeCompletionTUInfo;
-class CodeCompletionResult;
-class CoroutineBodyStmt;
-class Decl;
-class DeclAccessPair;
-class DeclContext;
-class DeclRefExpr;
-class DeclaratorDecl;
+enum class ComparisonCategoryType : unsigned char;
+class ConstraintSatisfaction;
+class DarwinSDKInfo;
+class DeclGroupRef;
 class DeducedTemplateArgument;
+struct DeductionFailureInfo;
 class DependentDiagnostic;
-class DesignatedInitExpr;
 class Designation;
-class EnableIfAttr;
-class EnumConstantDecl;
-class Expr;
-class ExtVectorType;
-class FormatAttr;
-class FriendDecl;
-class FunctionDecl;
-class FunctionProtoType;
-class FunctionTemplateDecl;
+class IdentifierInfo;
 class ImplicitConversionSequence;
 typedef MutableArrayRef<ImplicitConversionSequence> ConversionSequenceList;
-class InitListExpr;
 class InitializationKind;
 class InitializationSequence;
 class InitializedEntity;
-class IntegerLiteral;
-class LabelStmt;
-class LambdaExpr;
-class LangOptions;
+enum class LangAS : unsigned int;
 class LocalInstantiationScope;
 class LookupResult;
-class MacroInfo;
+class MangleNumberingContext;
 typedef ArrayRef<std::pair<IdentifierInfo *, SourceLocation>> ModuleIdPath;
 class ModuleLoader;
 class MultiLevelTemplateArgumentList;
-class NamedDecl;
-class ObjCImplementationDecl;
+struct NormalizedConstraint;
 class ObjCInterfaceDecl;
 class ObjCMethodDecl;
-class ObjCProtocolDecl;
 struct OverloadCandidate;
 enum class OverloadCandidateParamOrder : char;
 enum OverloadCandidateRewriteKind : unsigned;
 class OverloadCandidateSet;
-class OverloadExpr;
-class ParenListExpr;
-class ParmVarDecl;
 class Preprocessor;
-class PseudoDestructorTypeStorage;
-class PseudoObjectExpr;
-class QualType;
 class SemaAMDGPU;
 class SemaARM;
 class SemaAVR;
@@ -196,41 +178,19 @@ class SemaSystemZ;
 class SemaWasm;
 class SemaX86;
 class StandardConversionSequence;
-class Stmt;
-class StringLiteral;
-class SwitchStmt;
 class TemplateArgument;
-class TemplateArgumentList;
 class TemplateArgumentLoc;
-class TemplateDecl;
 class TemplateInstantiationCallback;
-class TemplateParameterList;
 class TemplatePartialOrderingContext;
-class TemplateTemplateParmDecl;
+class TemplateSpecCandidateSet;
 class Token;
-class TypeAliasDecl;
-class TypedefDecl;
-class TypedefNameDecl;
-class TypeLoc;
+class TypeConstraint;
 class TypoCorrectionConsumer;
-class UnqualifiedId;
-class UnresolvedLookupExpr;
-class UnresolvedMemberExpr;
 class UnresolvedSetImpl;
 class UnresolvedSetIterator;
-class UsingDecl;
-class UsingShadowDecl;
-class ValueDecl;
-class VarDecl;
-class VarTemplateSpecializationDecl;
-class VisibilityAttr;
 class VisibleDeclConsumer;
-class IndirectFieldDecl;
-struct DeductionFailureInfo;
-class TemplateSpecCandidateSet;
 
 namespace sema {
-class AccessedEntity;
 class BlockScopeInfo;
 class Capture;
 class CapturedRegionScopeInfo;
@@ -240,8 +200,6 @@ class DelayedDiagnostic;
 class DelayedDiagnosticPool;
 class FunctionScopeInfo;
 class LambdaScopeInfo;
-class PossiblyUnreachableDiag;
-class RISCVIntrinsicManager;
 class SemaPPCallbacks;
 class TemplateDeductionInfo;
 } // namespace sema

clang/include/clang/Sema/SemaAMDGPU.h

@@ -13,14 +13,13 @@
 #ifndef LLVM_CLANG_SEMA_SEMAAMDGPU_H
 #define LLVM_CLANG_SEMA_SEMAAMDGPU_H
 
-#include "clang/AST/Attr.h"
-#include "clang/AST/DeclBase.h"
-#include "clang/AST/Expr.h"
-#include "clang/Basic/AttributeCommonInfo.h"
-#include "clang/Sema/ParsedAttr.h"
+#include "clang/AST/ASTFwd.h"
 #include "clang/Sema/SemaBase.h"
 
 namespace clang {
+class AttributeCommonInfo;
+class ParsedAttr;
+
 class SemaAMDGPU : public SemaBase {
 public:
   SemaAMDGPU(Sema &S);

clang/include/clang/Sema/SemaARM.h

@@ -13,15 +13,18 @@
 #ifndef LLVM_CLANG_SEMA_SEMAARM_H
 #define LLVM_CLANG_SEMA_SEMAARM_H
 
-#include "clang/AST/DeclBase.h"
-#include "clang/AST/Expr.h"
-#include "clang/Basic/TargetInfo.h"
+#include "clang/AST/ASTFwd.h"
 #include "clang/Sema/SemaBase.h"
-#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
 #include <tuple>
 
+namespace llvm {
+template <typename T, unsigned N> class SmallVector;
+} // namespace llvm
+
 namespace clang {
 class ParsedAttr;
+class TargetInfo;
 
 class SemaARM : public SemaBase {
 public:
@@ -60,10 +63,10 @@ class SemaARM : public SemaBase {
                             unsigned ExpectedFieldNum, bool AllowName);
   bool BuiltinARMMemoryTaggingCall(unsigned BuiltinID, CallExpr *TheCall);
 
-  bool MveAliasValid(unsigned BuiltinID, StringRef AliasName);
-  bool CdeAliasValid(unsigned BuiltinID, StringRef AliasName);
-  bool SveAliasValid(unsigned BuiltinID, StringRef AliasName);
-  bool SmeAliasValid(unsigned BuiltinID, StringRef AliasName);
+  bool MveAliasValid(unsigned BuiltinID, llvm::StringRef AliasName);
+  bool CdeAliasValid(unsigned BuiltinID, llvm::StringRef AliasName);
+  bool SveAliasValid(unsigned BuiltinID, llvm::StringRef AliasName);
+  bool SmeAliasValid(unsigned BuiltinID, llvm::StringRef AliasName);
   void handleBuiltinAliasAttr(Decl *D, const ParsedAttr &AL);
   void handleNewAttr(Decl *D, const ParsedAttr &AL);
   void handleCmseNSEntryAttr(Decl *D, const ParsedAttr &AL);

clang/include/clang/Sema/SemaAVR.h

@@ -13,10 +13,10 @@
 #ifndef LLVM_CLANG_SEMA_SEMAAVR_H
 #define LLVM_CLANG_SEMA_SEMAAVR_H
 
+#include "clang/AST/ASTFwd.h"
 #include "clang/Sema/SemaBase.h"
 
 namespace clang {
-class Decl;
 class ParsedAttr;
 
 class SemaAVR : public SemaBase {

clang/include/clang/Sema/SemaBPF.h

@@ -13,9 +13,7 @@
 #ifndef LLVM_CLANG_SEMA_SEMABPF_H
 #define LLVM_CLANG_SEMA_SEMABPF_H
 
-#include "clang/AST/Decl.h"
-#include "clang/AST/DeclBase.h"
-#include "clang/AST/Expr.h"
+#include "clang/AST/ASTFwd.h"
 #include "clang/Sema/SemaBase.h"
 
 namespace clang {

clang/include/clang/Sema/SemaCUDA.h

@@ -13,24 +13,34 @@
 #ifndef LLVM_CLANG_SEMA_SEMACUDA_H
 #define LLVM_CLANG_SEMA_SEMACUDA_H
 
-#include "clang/AST/Decl.h"
-#include "clang/AST/DeclCXX.h"
+#include "clang/AST/ASTFwd.h"
+#include "clang/AST/DeclAccessPair.h"
 #include "clang/AST/Redeclarable.h"
 #include "clang/Basic/Cuda.h"
+#include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Sema/Lookup.h"
 #include "clang/Sema/Ownership.h"
-#include "clang/Sema/ParsedAttr.h"
-#include "clang/Sema/Scope.h"
-#include "clang/Sema/ScopeInfo.h"
 #include "clang/Sema/SemaBase.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/SmallVector.h"
 #include <string>
+#include <utility>
 
 namespace clang {
+namespace sema {
+class Capture;
+} // namespace sema
 
+class ASTReader;
+class ASTWriter;
 enum class CUDAFunctionTarget;
+enum class CXXSpecialMemberKind;
+class ParsedAttributesView;
+class Scope;
 
 class SemaCUDA : public SemaBase {
 public: