TypeSystem.h

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//===-- TypeSystem.h ------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#ifndef LLDB_SYMBOL_TYPESYSTEM_H
#define LLDB_SYMBOL_TYPESYSTEM_H
 
#include <functional>
#include <mutex>
#include <optional>
#include <string>
 
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/JSON.h"
 
#include "lldb/Core/PluginInterface.h"
#include "lldb/Expression/Expression.h"
#include "lldb/Symbol/CompilerDecl.h"
#include "lldb/Symbol/CompilerDeclContext.h"
#include "lldb/Symbol/Type.h"
#include "lldb/Utility/Scalar.h"
#include "lldb/lldb-forward.h"
#include "lldb/lldb-private.h"
#include "lldb/lldb-types.h"
 
class PDBASTParser;
 
namespace lldb_private {
 
namespace plugin {
namespace dwarf {
class DWARFDIE;
class DWARFASTParser;
} // namespace dwarf
} // namespace plugin
 
namespace npdb {
  class PdbAstBuilder;
} // namespace npdb
 
/// Interface for representing a type system.
///
/// Implemented by language plugins to define the type system for a given
/// language.
///
/// This interface extensively used opaque pointers to prevent that generic
/// LLDB code has dependencies on language plugins. The type and semantics of
/// these opaque pointers are defined by the TypeSystem implementation inside
/// the respective language plugin. Opaque pointers from one TypeSystem
/// instance should never be passed to a different TypeSystem instance (even
/// when the language plugin for both TypeSystem instances is the same).
///
/// Most of the functions in this class should not be called directly but only
/// called by their respective counterparts in CompilerType, CompilerDecl and
/// CompilerDeclContext.
///
/// \see lldb_private::CompilerType
/// \see lldb_private::CompilerDecl
/// \see lldb_private::CompilerDeclContext
class TypeSystem : public PluginInterface,
                   public std::enable_shared_from_this<TypeSystem> {
public:
  // Constructors and Destructors
  TypeSystem();
  ~TypeSystem() override;
 
  // LLVM RTTI support
  virtual bool isA(const void *ClassID) const = 0;
 
  static lldb::TypeSystemSP CreateInstance(lldb::LanguageType language,
                                           Module *module);
 
  static lldb::TypeSystemSP CreateInstance(lldb::LanguageType language,
                                           Target *target);
 
  /// Free up any resources associated with this TypeSystem.  Done before
  /// removing all the TypeSystems from the TypeSystemMap.
  virtual void Finalize() {}
 
  virtual plugin::dwarf::DWARFASTParser *GetDWARFParser() { return nullptr; }
 
  virtual PDBASTParser *GetPDBParser() { return nullptr; }
  virtual npdb::PdbAstBuilder *GetNativePDBParser() { return nullptr; }
 
  virtual SymbolFile *GetSymbolFile() const { return m_sym_file; }
 
  virtual void SetSymbolFile(SymbolFile *sym_file) { m_sym_file = sym_file; }
 
  // CompilerDecl functions
  virtual ConstString DeclGetName(void *opaque_decl) = 0;
 
  virtual ConstString DeclGetMangledName(void *opaque_decl);
 
  virtual CompilerDeclContext DeclGetDeclContext(void *opaque_decl);
 
  virtual CompilerType DeclGetFunctionReturnType(void *opaque_decl);
 
  virtual size_t DeclGetFunctionNumArguments(void *opaque_decl);
 
  virtual CompilerType DeclGetFunctionArgumentType(void *opaque_decl,
                                                   size_t arg_idx);
 
  virtual std::vector<lldb_private::CompilerContext>
  DeclGetCompilerContext(void *opaque_decl);
 
  virtual Scalar DeclGetConstantValue(void *opaque_decl) { return Scalar(); }
 
  virtual CompilerType GetTypeForDecl(void *opaque_decl) = 0;
 
  // CompilerDeclContext functions
 
  virtual std::vector<CompilerDecl>
  DeclContextFindDeclByName(void *opaque_decl_ctx, ConstString name,
                            const bool ignore_imported_decls);
 
  virtual ConstString DeclContextGetName(void *opaque_decl_ctx) = 0;
 
  virtual ConstString
  DeclContextGetScopeQualifiedName(void *opaque_decl_ctx) = 0;
 
  virtual bool DeclContextIsClassMethod(void *opaque_decl_ctx) = 0;
 
  virtual bool DeclContextIsContainedInLookup(void *opaque_decl_ctx,
                                              void *other_opaque_decl_ctx) = 0;
 
  virtual lldb::LanguageType DeclContextGetLanguage(void *opaque_decl_ctx) = 0;
 
  /// Returns the direct parent context of specified type
  virtual CompilerDeclContext
  GetCompilerDeclContextForType(const CompilerType &type);
 
  virtual std::vector<lldb_private::CompilerContext>
  DeclContextGetCompilerContext(void *opaque_decl_ctx);
 
  // Tests
#ifndef NDEBUG
  /// Verify the integrity of the type to catch CompilerTypes that mix
  /// and match invalid TypeSystem/Opaque type pairs.
  virtual bool Verify(lldb::opaque_compiler_type_t type) = 0;
#endif
 
  virtual bool IsArrayType(lldb::opaque_compiler_type_t type,
                           CompilerType *element_type, uint64_t *size,
                           bool *is_incomplete) = 0;
 
  virtual bool IsAggregateType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsAnonymousType(lldb::opaque_compiler_type_t type);
 
  virtual bool IsCharType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsCompleteType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsDefined(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsFloatingPointType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsFunctionType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual size_t
  GetNumberOfFunctionArguments(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType
  GetFunctionArgumentAtIndex(lldb::opaque_compiler_type_t type,
                             const size_t index) = 0;
 
  virtual bool IsFunctionPointerType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool
  IsMemberFunctionPointerType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsBlockPointerType(lldb::opaque_compiler_type_t type,
                                  CompilerType *function_pointer_type_ptr) = 0;
 
  virtual bool IsIntegerType(lldb::opaque_compiler_type_t type,
                             bool &is_signed) = 0;
 
  virtual bool IsEnumerationType(lldb::opaque_compiler_type_t type,
                                 bool &is_signed) {
    is_signed = false;
    return false;
  }
 
  virtual bool IsScopedEnumerationType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsPossibleDynamicType(lldb::opaque_compiler_type_t type,
                                     CompilerType *target_type, // Can pass NULL
                                     bool check_cplusplus, bool check_objc) = 0;
 
  virtual bool IsPointerType(lldb::opaque_compiler_type_t type,
                             CompilerType *pointee_type) = 0;
 
  virtual bool IsScalarType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsVoidType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool CanPassInRegisters(const CompilerType &type) = 0;
 
  // TypeSystems can support more than one language
  virtual bool SupportsLanguage(lldb::LanguageType language) = 0;
 
  static bool SupportsLanguageStatic(lldb::LanguageType language);
  // Type Completion
 
  virtual bool GetCompleteType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsForcefullyCompleted(lldb::opaque_compiler_type_t type) {
    return false;
  }
 
  // AST related queries
 
  virtual uint32_t GetPointerByteSize() = 0;
 
  virtual CompilerType GetPointerDiffType(bool is_signed) = 0;
 
  virtual unsigned GetPtrAuthKey(lldb::opaque_compiler_type_t type) = 0;
 
  virtual unsigned
  GetPtrAuthDiscriminator(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool
  GetPtrAuthAddressDiversity(lldb::opaque_compiler_type_t type) = 0;
 
  // Accessors
 
  virtual ConstString GetTypeName(lldb::opaque_compiler_type_t type,
                                  bool BaseOnly) = 0;
 
  virtual ConstString GetDisplayTypeName(lldb::opaque_compiler_type_t type) = 0;
 
  /// Defaults to GetTypeName(type).  Override if your language desires
  /// specialized behavior.
  virtual ConstString GetMangledTypeName(lldb::opaque_compiler_type_t type);
 
  virtual uint32_t
  GetTypeInfo(lldb::opaque_compiler_type_t type,
              CompilerType *pointee_or_element_compiler_type) = 0;
 
  virtual lldb::LanguageType
  GetMinimumLanguage(lldb::opaque_compiler_type_t type) = 0;
 
  virtual lldb::TypeClass GetTypeClass(lldb::opaque_compiler_type_t type) = 0;
 
  // Creating related types
 
  virtual CompilerType
  GetArrayElementType(lldb::opaque_compiler_type_t type,
                      ExecutionContextScope *exe_scope) = 0;
 
  virtual CompilerType GetArrayType(lldb::opaque_compiler_type_t type,
                                    uint64_t size);
 
  virtual CompilerType GetCanonicalType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType
  GetEnumerationIntegerType(lldb::opaque_compiler_type_t type) = 0;
 
  // Returns -1 if this isn't a function of if the function doesn't have a
  // prototype Returns a value >= 0 if there is a prototype.
  virtual int GetFunctionArgumentCount(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType
  GetFunctionArgumentTypeAtIndex(lldb::opaque_compiler_type_t type,
                                 size_t idx) = 0;
 
  virtual CompilerType
  GetFunctionReturnType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual size_t GetNumMemberFunctions(lldb::opaque_compiler_type_t type) = 0;
 
  virtual TypeMemberFunctionImpl
  GetMemberFunctionAtIndex(lldb::opaque_compiler_type_t type, size_t idx) = 0;
 
  virtual CompilerType GetPointeeType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType GetPointerType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType
  GetLValueReferenceType(lldb::opaque_compiler_type_t type);
 
  virtual CompilerType
  GetRValueReferenceType(lldb::opaque_compiler_type_t type);
 
  virtual CompilerType GetAtomicType(lldb::opaque_compiler_type_t type);
 
  virtual CompilerType AddConstModifier(lldb::opaque_compiler_type_t type);
 
  virtual CompilerType AddVolatileModifier(lldb::opaque_compiler_type_t type);
 
  virtual CompilerType AddRestrictModifier(lldb::opaque_compiler_type_t type);
 
  virtual CompilerType AddPtrAuthModifier(lldb::opaque_compiler_type_t type,
                                          uint32_t payload);
 
  /// \param opaque_payload      The m_payload field of Type, which may
  /// carry TypeSystem-specific extra information.
  virtual CompilerType CreateTypedef(lldb::opaque_compiler_type_t type,
                                     const char *name,
                                     const CompilerDeclContext &decl_ctx,
                                     uint32_t opaque_payload);
 
  // Exploring the type
 
  virtual const llvm::fltSemantics &
  GetFloatTypeSemantics(size_t byte_size, lldb::Format format) = 0;
 
  virtual llvm::Expected<uint64_t>
  GetBitSize(lldb::opaque_compiler_type_t type,
             ExecutionContextScope *exe_scope) = 0;
 
  virtual lldb::Encoding GetEncoding(lldb::opaque_compiler_type_t type) = 0;
 
  virtual lldb::Format GetFormat(lldb::opaque_compiler_type_t type) = 0;
 
  virtual llvm::Expected<uint32_t>
  GetNumChildren(lldb::opaque_compiler_type_t type,
                 bool omit_empty_base_classes,
                 const ExecutionContext *exe_ctx) = 0;
 
  virtual CompilerType GetBuiltinTypeByName(ConstString name);
 
  virtual lldb::BasicType
  GetBasicTypeEnumeration(lldb::opaque_compiler_type_t type) = 0;
 
  virtual void ForEachEnumerator(
      lldb::opaque_compiler_type_t type,
      std::function<bool(const CompilerType &integer_type,
                         ConstString name,
                         const llvm::APSInt &value)> const &callback) {}
 
  virtual uint32_t GetNumFields(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType GetFieldAtIndex(lldb::opaque_compiler_type_t type,
                                       size_t idx, std::string &name,
                                       uint64_t *bit_offset_ptr,
                                       uint32_t *bitfield_bit_size_ptr,
                                       bool *is_bitfield_ptr) = 0;
 
  virtual uint32_t
  GetNumDirectBaseClasses(lldb::opaque_compiler_type_t type) = 0;
 
  virtual uint32_t
  GetNumVirtualBaseClasses(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType
  GetDirectBaseClassAtIndex(lldb::opaque_compiler_type_t type, size_t idx,
                            uint32_t *bit_offset_ptr) = 0;
 
  virtual CompilerType
  GetVirtualBaseClassAtIndex(lldb::opaque_compiler_type_t type, size_t idx,
                             uint32_t *bit_offset_ptr) = 0;
 
  virtual CompilerDecl GetStaticFieldWithName(lldb::opaque_compiler_type_t type,
                                              llvm::StringRef name) {
    return CompilerDecl();
  }
 
  virtual llvm::Expected<CompilerType>
  GetDereferencedType(lldb::opaque_compiler_type_t type,
                      ExecutionContext *exe_ctx, std::string &deref_name,
                      uint32_t &deref_byte_size, int32_t &deref_byte_offset,
                      ValueObject *valobj, uint64_t &language_flags) = 0;
 
  virtual llvm::Expected<CompilerType> GetChildCompilerTypeAtIndex(
      lldb::opaque_compiler_type_t type, ExecutionContext *exe_ctx, size_t idx,
      bool transparent_pointers, bool omit_empty_base_classes,
      bool ignore_array_bounds, std::string &child_name,
      uint32_t &child_byte_size, int32_t &child_byte_offset,
      uint32_t &child_bitfield_bit_size, uint32_t &child_bitfield_bit_offset,
      bool &child_is_base_class, bool &child_is_deref_of_parent,
      ValueObject *valobj, uint64_t &language_flags) = 0;
 
  // Lookup a child given a name. This function will match base class names and
  // member member names in "clang_type" only, not descendants.
  virtual llvm::Expected<uint32_t>
  GetIndexOfChildWithName(lldb::opaque_compiler_type_t type,
                          llvm::StringRef name,
                          bool omit_empty_base_classes) = 0;
 
  virtual size_t GetIndexOfChildMemberWithName(
      lldb::opaque_compiler_type_t type, llvm::StringRef name,
      bool omit_empty_base_classes, std::vector<uint32_t> &child_indexes) = 0;
 
  virtual CompilerType
  GetDirectNestedTypeWithName(lldb::opaque_compiler_type_t type,
                              llvm::StringRef name) {
    return CompilerType();
  }
 
  virtual bool IsTemplateType(lldb::opaque_compiler_type_t type);
 
  virtual size_t GetNumTemplateArguments(lldb::opaque_compiler_type_t type,
                                         bool expand_pack);
 
  virtual lldb::TemplateArgumentKind
  GetTemplateArgumentKind(lldb::opaque_compiler_type_t type, size_t idx,
                          bool expand_pack);
  virtual CompilerType
  GetTypeTemplateArgument(lldb::opaque_compiler_type_t type, size_t idx,
                          bool expand_pack);
  virtual std::optional<CompilerType::IntegralTemplateArgument>
  GetIntegralTemplateArgument(lldb::opaque_compiler_type_t type, size_t idx,
                              bool expand_pack);
 
  // DIL
 
  /// Checks if the type is eligible for integral promotion.
  virtual bool IsPromotableIntegerType(lldb::opaque_compiler_type_t type);
 
  /// Perform integral promotion on a given type.
  /// This promotes eligible types (boolean, integers, unscoped enumerations)
  /// to a larger integer type according to type system rules.
  /// \returns Promoted type.
  virtual llvm::Expected<CompilerType>
  DoIntegralPromotion(CompilerType from, ExecutionContextScope *exe_scope);
 
  // Dumping types
 
#ifndef NDEBUG
  /// Convenience LLVM-style dump method for use in the debugger only.
  LLVM_DUMP_METHOD virtual void
  dump(lldb::opaque_compiler_type_t type) const = 0;
#endif
 
  virtual bool DumpTypeValue(lldb::opaque_compiler_type_t type, Stream &s,
                             lldb::Format format, const DataExtractor &data,
                             lldb::offset_t data_offset, size_t data_byte_size,
                             uint32_t bitfield_bit_size,
                             uint32_t bitfield_bit_offset,
                             ExecutionContextScope *exe_scope) = 0;
 
  /// Dump the type to stdout.
  virtual void DumpTypeDescription(
      lldb::opaque_compiler_type_t type,
      lldb::DescriptionLevel level = lldb::eDescriptionLevelFull) = 0;
 
  /// Print a description of the type to a stream. The exact implementation
  /// varies, but the expectation is that eDescriptionLevelFull returns a
  /// source-like representation of the type, whereas eDescriptionLevelVerbose
  /// does a dump of the underlying AST if applicable.
  virtual void DumpTypeDescription(
      lldb::opaque_compiler_type_t type, Stream &s,
      lldb::DescriptionLevel level = lldb::eDescriptionLevelFull) = 0;
 
  /// Dump a textual representation of the internal TypeSystem state to the
  /// given stream.
  ///
  /// This should not modify the state of the TypeSystem if possible.
  ///
  /// \param[out] output Stream to dup the AST into.
  /// \param[in] filter If empty, dump whole AST. If non-empty, will only
  /// dump decls whose names contain \c filter.
  /// \param[in] show_color If true, prints the AST color-highlighted.
  virtual void Dump(llvm::raw_ostream &output, llvm::StringRef filter,
                    bool show_color) = 0;
 
  /// This is used by swift.
  virtual bool IsRuntimeGeneratedType(lldb::opaque_compiler_type_t type) = 0;
 
  // TODO: Determine if these methods should move to TypeSystemClang.
 
  virtual bool IsPointerOrReferenceType(lldb::opaque_compiler_type_t type,
                                        CompilerType *pointee_type) = 0;
 
  virtual unsigned GetTypeQualifiers(lldb::opaque_compiler_type_t type) = 0;
 
  virtual std::optional<size_t>
  GetTypeBitAlign(lldb::opaque_compiler_type_t type,
                  ExecutionContextScope *exe_scope) = 0;
 
  virtual CompilerType GetBasicTypeFromAST(lldb::BasicType basic_type) = 0;
 
  virtual CompilerType CreateGenericFunctionPrototype() {
    return CompilerType();
  }
 
  virtual CompilerType
  GetBuiltinTypeForEncodingAndBitSize(lldb::Encoding encoding,
                                      size_t bit_size) = 0;
 
  virtual bool IsBeingDefined(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsConst(lldb::opaque_compiler_type_t type) = 0;
 
  virtual uint32_t IsHomogeneousAggregate(lldb::opaque_compiler_type_t type,
                                          CompilerType *base_type_ptr) = 0;
 
  virtual bool IsPolymorphicClass(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsTypedefType(lldb::opaque_compiler_type_t type) = 0;
 
  // If the current object represents a typedef type, get the underlying type
  virtual CompilerType GetTypedefedType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsVectorType(lldb::opaque_compiler_type_t type,
                            CompilerType *element_type, uint64_t *size) = 0;
 
  virtual CompilerType
  GetFullyUnqualifiedType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual CompilerType
  GetNonReferenceType(lldb::opaque_compiler_type_t type) = 0;
 
  virtual bool IsReferenceType(lldb::opaque_compiler_type_t type,
                               CompilerType *pointee_type, bool *is_rvalue) = 0;
 
  virtual bool
  ShouldTreatScalarValueAsAddress(lldb::opaque_compiler_type_t type) {
    return IsPointerOrReferenceType(type, nullptr);
  }
 
  virtual UserExpression *GetUserExpression(
      llvm::StringRef expr, llvm::StringRef prefix, SourceLanguage language,
      Expression::ResultType desired_type,
      const EvaluateExpressionOptions &options, ValueObject *ctx_obj) {
    return nullptr;
  }
 
  virtual FunctionCaller *GetFunctionCaller(const CompilerType &return_type,
                                            const Address &function_address,
                                            const ValueList &arg_value_list,
                                            const char *name) {
    return nullptr;
  }
 
  virtual std::unique_ptr<UtilityFunction>
  CreateUtilityFunction(std::string text, std::string name);
 
  virtual PersistentExpressionState *GetPersistentExpressionState() {
    return nullptr;
  }
 
  virtual CompilerType GetTypeForFormatters(void *type);
 
  virtual LazyBool ShouldPrintAsOneLiner(void *type, ValueObject *valobj);
 
  // Type systems can have types that are placeholder types, which are meant to
  // indicate the presence of a type, but offer no actual information about
  // said types, and leave the burden of actually figuring type information out
  // to dynamic type resolution. For instance a language with a generics
  // system, can use placeholder types to indicate "type argument goes here",
  // without promising uniqueness of the placeholder, nor attaching any
  // actually idenfiable information to said placeholder. This API allows type
  // systems to tell LLDB when such a type has been encountered In response,
  // the debugger can react by not using this type as a cache entry in any
  // type-specific way For instance, LLDB will currently not cache any
  // formatters that are discovered on such a type as attributable to the
  // meaningless type itself, instead preferring to use the dynamic type
  virtual bool IsMeaninglessWithoutDynamicResolution(void *type);
 
  virtual std::optional<llvm::json::Value> ReportStatistics();
 
  bool GetHasForcefullyCompletedTypes() const {
    return m_has_forcefully_completed_types;
  }
protected:
  SymbolFile *m_sym_file = nullptr;
  /// Used for reporting statistics.
  bool m_has_forcefully_completed_types = false;
};
 
class TypeSystemMap {
public:
  TypeSystemMap();
  ~TypeSystemMap();
 
  // Clear calls Finalize on all the TypeSystems managed by this map, and then
  // empties the map.
  void Clear();
 
  // Iterate through all of the type systems that are created. Return true from
  // callback to keep iterating, false to stop iterating.
  void ForEach(std::function<bool(lldb::TypeSystemSP)> const &callback);
 
  llvm::Expected<lldb::TypeSystemSP>
  GetTypeSystemForLanguage(lldb::LanguageType language, Module *module,
                           bool can_create);
 
  llvm::Expected<lldb::TypeSystemSP>
  GetTypeSystemForLanguage(lldb::LanguageType language, Target *target,
                           bool can_create);
 
  /// Check all type systems in the map to see if any have forcefully completed
  /// types;
  bool GetHasForcefullyCompletedTypes() const;
protected:
  typedef llvm::DenseMap<uint16_t, lldb::TypeSystemSP> collection;
  mutable std::mutex m_mutex; ///< A mutex to keep this object happy in
                              /// multi-threaded environments.
  collection m_map;
  bool m_clear_in_progress = false;
 
private:
  typedef llvm::function_ref<lldb::TypeSystemSP()> CreateCallback;
  /// Finds the type system for the given language. If no type system could be
  /// found for a language and a CreateCallback was provided, the value
  /// returned by the callback will be treated as the TypeSystem for the
  /// language.
  ///
  /// \param language The language for which the type system should be found.
  /// \param create_callback A callback that will be called if no previously
  ///                        created TypeSystem that fits the given language
  ///                        could found. Can be omitted if a non-existent
  ///                        type system should be treated as an error
  ///                        instead.
  /// \return The found type system or an error.
  llvm::Expected<lldb::TypeSystemSP> GetTypeSystemForLanguage(
      lldb::LanguageType language,
      std::optional<CreateCallback> create_callback = std::nullopt);
  };
 
  } // namespace lldb_private
 
#endif // LLDB_SYMBOL_TYPESYSTEM_H