ArgsToFrontendOptionsConverter.cpp

//===--- ArgsToFrontendOptionsConverter -----------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#include "ArgsToFrontendOptionsConverter.h"

#include "ArgsToFrontendInputsConverter.h"
#include "ArgsToFrontendOutputsConverter.h"
#include "swift/AST/DiagnosticsFrontend.h"
#include "swift/Basic/Platform.h"
#include "swift/Frontend/Frontend.h"
#include "swift/Option/Options.h"
#include "swift/Option/SanitizerOptions.h"
#include "swift/Parse/Lexer.h"
#include "swift/Strings.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Option/Arg.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Option/Option.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/LineIterator.h"
#include "llvm/Support/Path.h"

using namespace swift;
using namespace llvm::opt;

// This is a separate function so that it shows up in stack traces.
LLVM_ATTRIBUTE_NOINLINE
static void debugFailWithAssertion() {
  // This assertion should always fail, per the user's request, and should
  // not be converted to llvm_unreachable.
  assert(0 && "This is an assertion!");
}

// This is a separate function so that it shows up in stack traces.
LLVM_ATTRIBUTE_NOINLINE
static void debugFailWithCrash() { LLVM_BUILTIN_TRAP; }

bool ArgsToFrontendOptionsConverter::convert(
    SmallVectorImpl<std::unique_ptr<llvm::MemoryBuffer>> *buffers) {
  using namespace options;

  handleDebugCrashGroupArguments();

  if (const Arg *A = Args.getLastArg(OPT_dump_api_path)) {
    Opts.DumpAPIPath = A->getValue();
  }
  if (const Arg *A = Args.getLastArg(OPT_group_info_path)) {
    Opts.GroupInfoPath = A->getValue();
  }
  if (const Arg *A = Args.getLastArg(OPT_index_store_path)) {
    Opts.IndexStorePath = A->getValue();
  }
  if (const Arg *A = Args.getLastArg(OPT_prebuilt_module_cache_path)) {
    Opts.PrebuiltModuleCachePath = A->getValue();
  }
  if (const Arg *A = Args.getLastArg(OPT_backup_module_interface_path)) {
    Opts.BackupModuleInterfaceDir = A->getValue();
  }
  if (const Arg *A = Args.getLastArg(OPT_bridging_header_directory_for_print)) {
    Opts.BridgingHeaderDirForPrint = A->getValue();
  }
  Opts.IndexIgnoreClangModules |= Args.hasArg(OPT_index_ignore_clang_modules);
  Opts.IndexSystemModules |= Args.hasArg(OPT_index_system_modules);
  Opts.IndexIgnoreStdlib |= Args.hasArg(OPT_index_ignore_stdlib);
  Opts.IndexIncludeLocals |= Args.hasArg(OPT_index_include_locals);

  Opts.EmitVerboseSIL |= Args.hasArg(OPT_emit_verbose_sil);
  Opts.EmitSortedSIL |= Args.hasArg(OPT_emit_sorted_sil);
  Opts.PrintFullConvention |=
      Args.hasArg(OPT_experimental_print_full_convention);

  Opts.EnableTesting |= Args.hasArg(OPT_enable_testing);
  Opts.EnablePrivateImports |= Args.hasArg(OPT_enable_private_imports);
  Opts.EnableLibraryEvolution |= Args.hasArg(OPT_enable_library_evolution);
  Opts.FrontendParseableOutput |= Args.hasArg(OPT_frontend_parseable_output);
  Opts.ExplicitInterfaceBuild |= Args.hasArg(OPT_explicit_interface_module_build);

  // FIXME: Remove this flag
  Opts.EnableLibraryEvolution |= Args.hasArg(OPT_enable_resilience);

  Opts.EnableImplicitDynamic |= Args.hasArg(OPT_enable_implicit_dynamic);

  if (Args.hasArg(OPT_track_system_dependencies)) {
    Opts.IntermoduleDependencyTracking =
        IntermoduleDepTrackingMode::IncludeSystem;
  } else if (Args.hasArg(OPT_explicit_interface_module_build)) {
    // Always track at least the non-system dependencies for interface building.
    Opts.IntermoduleDependencyTracking =
        IntermoduleDepTrackingMode::ExcludeSystem;
  }

  if (const Arg *A = Args.getLastArg(OPT_bad_file_descriptor_retry_count)) {
    unsigned limit;
    if (StringRef(A->getValue()).getAsInteger(10, limit)) {
      Diags.diagnose(SourceLoc(), diag::error_invalid_arg_value,
                     A->getAsString(Args), A->getValue());
      return true;
    }
    Opts.BadFileDescriptorRetryCount = limit;
  }

  if (auto A = Args.getLastArg(OPT_user_module_version)) {
    StringRef raw(A->getValue());
    while(raw.count('.') > 3) {
      raw = raw.rsplit('.').first;
    }
    if (Opts.UserModuleVersion.tryParse(raw)) {
      Diags.diagnose(SourceLoc(), diag::error_invalid_arg_value,
                     A->getAsString(Args), A->getValue());
    }
  }

  Opts.DisableImplicitModules |= Args.hasArg(OPT_disable_implicit_swift_modules);

  Opts.ImportPrescan |= Args.hasArg(OPT_import_prescan);

  Opts.SerializeDependencyScannerCache |= Args.hasArg(OPT_serialize_dependency_scan_cache);
  Opts.ReuseDependencyScannerCache |= Args.hasArg(OPT_reuse_dependency_scan_cache);
  Opts.EmitDependencyScannerCacheRemarks |= Args.hasArg(OPT_dependency_scan_cache_remarks);
  if (const Arg *A = Args.getLastArg(OPT_dependency_scan_cache_path)) {
    Opts.SerializedDependencyScannerCachePath = A->getValue();
  }

  Opts.DisableCrossModuleIncrementalBuild |=
      Args.hasArg(OPT_disable_incremental_imports);

  // Always track system dependencies when scanning dependencies.
  if (const Arg *ModeArg = Args.getLastArg(OPT_modes_Group)) {
    if (ModeArg->getOption().matches(OPT_scan_dependencies)) {
      Opts.IntermoduleDependencyTracking =
          IntermoduleDepTrackingMode::IncludeSystem;
    }
  }

  Opts.SerializeModuleInterfaceDependencyHashes |=
    Args.hasArg(OPT_serialize_module_interface_dependency_hashes);

  Opts.RemarkOnRebuildFromModuleInterface |=
    Args.hasArg(OPT_Rmodule_interface_rebuild);

  Opts.DowngradeInterfaceVerificationError |=
    Args.hasArg(OPT_downgrade_typecheck_interface_error);
  computePrintStatsOptions();
  computeDebugTimeOptions();
  computeTBDOptions();

  Opts.CheckOnoneSupportCompleteness = Args.hasArg(OPT_check_onone_completeness);

  Opts.ParseStdlib |= Args.hasArg(OPT_parse_stdlib);

  Opts.IgnoreSwiftSourceInfo |= Args.hasArg(OPT_ignore_module_source_info);
  computeHelpOptions();

  if (Args.hasArg(OPT_print_target_info)) {
    Opts.PrintTargetInfo = true;
  }

  if (const Arg *A = Args.getLastArg(OPT_verify_generic_signatures)) {
    Opts.VerifyGenericSignaturesInModule = A->getValue();
  }

  Opts.AllowModuleWithCompilerErrors |= Args.hasArg(OPT_experimental_allow_module_with_compiler_errors);

  computeDumpScopeMapLocations();

  Optional<FrontendInputsAndOutputs> inputsAndOutputs =
      ArgsToFrontendInputsConverter(Diags, Args).convert(buffers);

  // None here means error, not just "no inputs". Propagate unconditionally.
  if (!inputsAndOutputs)
    return true;

  // InputsAndOutputs can only get set up once; if it was set already when we
  // entered this function, we should not set it again (and should assert this
  // is not being done). Further, the computeMainAndSupplementaryOutputFilenames
  // call below needs to only happen when there was a new InputsAndOutputs,
  // since it clobbers the existing one rather than adding to it.
  bool HaveNewInputsAndOutputs = false;
  if (Opts.InputsAndOutputs.hasInputs()) {
    assert(!inputsAndOutputs->hasInputs());
  } else {
    HaveNewInputsAndOutputs = true;
    Opts.InputsAndOutputs = std::move(inputsAndOutputs).getValue();
    if (Opts.AllowModuleWithCompilerErrors)
      Opts.InputsAndOutputs.setShouldRecoverMissingInputs();
  }

  if (Args.hasArg(OPT_parse_sil) || Opts.InputsAndOutputs.shouldTreatAsSIL()) {
    Opts.InputMode = FrontendOptions::ParseInputMode::SIL;
  } else if (Opts.InputsAndOutputs.shouldTreatAsModuleInterface()) {
    Opts.InputMode = FrontendOptions::ParseInputMode::SwiftModuleInterface;
  } else if (Args.hasArg(OPT_parse_as_library)) {
    Opts.InputMode = FrontendOptions::ParseInputMode::SwiftLibrary;
  } else {
    Opts.InputMode = FrontendOptions::ParseInputMode::Swift;
  }

  if (Opts.RequestedAction == FrontendOptions::ActionType::NoneAction) {
    Opts.RequestedAction = determineRequestedAction(Args);
  }

  if (Opts.RequestedAction == FrontendOptions::ActionType::CompileModuleFromInterface ||
      Opts.RequestedAction == FrontendOptions::ActionType::TypecheckModuleFromInterface) {
    // The situations where we use this action, e.g. explicit module building and
    // generating prebuilt module cache, don't need synchronization. We should avoid
    // using lock files for them.
    Opts.DisableInterfaceFileLock = true;
  } else {
    Opts.DisableInterfaceFileLock |= Args.hasArg(OPT_disable_interface_lockfile);
  }

  if (Opts.RequestedAction == FrontendOptions::ActionType::Immediate &&
      Opts.InputsAndOutputs.hasPrimaryInputs()) {
    Diags.diagnose(SourceLoc(), diag::error_immediate_mode_primary_file);
    return true;
  }

  if (setUpImmediateArgs())
    return true;

  if (computeModuleName())
    return true;

  if (HaveNewInputsAndOutputs &&
      computeMainAndSupplementaryOutputFilenames())
    return true;

  if (checkUnusedSupplementaryOutputPaths())
    return true;

  if (checkBuildFromInterfaceOnlyOptions())
    return true;

  if (FrontendOptions::doesActionGenerateIR(Opts.RequestedAction)) {
    if (Args.hasArg(OPT_experimental_skip_non_inlinable_function_bodies) ||
        Args.hasArg(OPT_experimental_skip_all_function_bodies) ||
        Args.hasArg(
         OPT_experimental_skip_non_inlinable_function_bodies_without_types)) {
      Diags.diagnose(SourceLoc(), diag::cannot_emit_ir_skipping_function_bodies);
      return true;
    }

    if (Args.hasArg(OPT_check_api_availability_only)) {
      Diags.diagnose(SourceLoc(), diag::cannot_emit_ir_checking_api_availability_only);
      return true;
    }
  }

  if (const Arg *A = Args.getLastArg(OPT_module_abi_name))
    Opts.ModuleABIName = A->getValue();

  if (const Arg *A = Args.getLastArg(OPT_module_link_name))
    Opts.ModuleLinkName = A->getValue();

  // This must be called after computing module name, module abi name,
  // and module link name. If computing module aliases is unsuccessful,
  // return early.
  if (!computeModuleAliases())
    return true;

  if (const Arg *A = Args.getLastArg(OPT_access_notes_path))
    Opts.AccessNotesPath = A->getValue();

  if (const Arg *A = Args.getLastArg(OPT_serialize_debugging_options,
                                     OPT_no_serialize_debugging_options)) {
    Opts.SerializeOptionsForDebugging =
        A->getOption().matches(OPT_serialize_debugging_options);
  }

  Opts.DebugPrefixSerializedDebuggingOptions |=
      Args.hasArg(OPT_prefix_serialized_debugging_options);
  Opts.EnableSourceImport |= Args.hasArg(OPT_enable_source_import);
  Opts.ImportUnderlyingModule |= Args.hasArg(OPT_import_underlying_module);
  Opts.EnableIncrementalDependencyVerifier |= Args.hasArg(OPT_verify_incremental_dependencies);
  Opts.UseSharedResourceFolder = !Args.hasArg(OPT_use_static_resource_dir);
  Opts.DisableBuildingInterface = Args.hasArg(OPT_disable_building_interface);
  if (const Arg *A = Args.getLastArg(options::OPT_clang_header_expose_decls)) {
      Opts.ClangHeaderExposedDecls =
          llvm::StringSwitch<llvm::Optional<FrontendOptions::ClangHeaderExposeBehavior>>(A->getValue())
              .Case("all-public", FrontendOptions::ClangHeaderExposeBehavior::AllPublic)
              .Case("has-expose-attr", FrontendOptions::ClangHeaderExposeBehavior::HasExposeAttr)
              .Default(llvm::None);
  }
  Opts.EnableExperimentalCxxInteropInClangHeader =
      Args.hasArg(OPT_enable_experimental_cxx_interop_in_clang_header);
  
  Opts.StrictImplicitModuleContext = Args.hasArg(OPT_strict_implicit_module_context,
                                                 OPT_no_strict_implicit_module_context,
                                                 false);

  computeImportObjCHeaderOptions();
  computeImplicitImportModuleNames(OPT_import_module, /*isTestable=*/false);
  computeImplicitImportModuleNames(OPT_testable_import_module, /*isTestable=*/true);
  computeLLVMArgs();

  Opts.EmitSymbolGraph |= Args.hasArg(OPT_emit_symbol_graph);
  
  if (const Arg *A = Args.getLastArg(OPT_emit_symbol_graph_dir)) {
    Opts.SymbolGraphOutputDir = A->getValue();
  }
  
  Opts.SkipInheritedDocs = Args.hasArg(OPT_skip_inherited_docs);
  Opts.IncludeSPISymbolsInSymbolGraph = Args.hasArg(OPT_include_spi_symbols);

  Opts.Static = Args.hasArg(OPT_static);

  Opts.HermeticSealAtLink = Args.hasArg(OPT_experimental_hermetic_seal_at_link);

  for (auto A : Args.getAllArgValues(options::OPT_serialized_path_obfuscate)) {
    auto SplitMap = StringRef(A).split('=');
    Opts.serializedPathObfuscator.addMapping(SplitMap.first, SplitMap.second);
  }
  Opts.emptyABIDescriptor = Args.hasArg(OPT_empty_abi_descriptor);
  return false;
}

void ArgsToFrontendOptionsConverter::handleDebugCrashGroupArguments() {
  using namespace options;

  if (const Arg *A = Args.getLastArg(OPT_debug_crash_Group)) {
    Option Opt = A->getOption();
    if (Opt.matches(OPT_debug_assert_immediately)) {
      debugFailWithAssertion();
    } else if (Opt.matches(OPT_debug_crash_immediately)) {
      debugFailWithCrash();
    } else if (Opt.matches(OPT_debug_assert_after_parse)) {
      // Set in FrontendOptions
      Opts.CrashMode = FrontendOptions::DebugCrashMode::AssertAfterParse;
    } else if (Opt.matches(OPT_debug_crash_after_parse)) {
      // Set in FrontendOptions
      Opts.CrashMode = FrontendOptions::DebugCrashMode::CrashAfterParse;
    } else {
      llvm_unreachable("Unknown debug_crash_Group option!");
    }
  }
}

void ArgsToFrontendOptionsConverter::computePrintStatsOptions() {
  using namespace options;
  Opts.PrintStats |= Args.hasArg(OPT_print_stats);
  Opts.PrintClangStats |= Args.hasArg(OPT_print_clang_stats);
#if defined(NDEBUG) && !defined(LLVM_ENABLE_STATS)
  if (Opts.PrintStats || Opts.PrintClangStats)
    Diags.diagnose(SourceLoc(), diag::stats_disabled);
#endif
}

void ArgsToFrontendOptionsConverter::computeDebugTimeOptions() {
  using namespace options;
  if (const Arg *A = Args.getLastArg(OPT_stats_output_dir)) {
    Opts.StatsOutputDir = A->getValue();
    if (Args.getLastArg(OPT_trace_stats_events)) {
      Opts.TraceStats = true;
    }
    if (Args.getLastArg(OPT_profile_stats_events)) {
      Opts.ProfileEvents = true;
    }
    if (Args.getLastArg(OPT_profile_stats_entities)) {
      Opts.ProfileEntities = true;
    }
  }
}

void ArgsToFrontendOptionsConverter::computeTBDOptions() {
  using namespace options;
  if (const Arg *A = Args.getLastArg(OPT_validate_tbd_against_ir_EQ)) {
    using Mode = FrontendOptions::TBDValidationMode;
    StringRef value = A->getValue();
    if (value == "none") {
      Opts.ValidateTBDAgainstIR = Mode::None;
    } else if (value == "missing") {
      Opts.ValidateTBDAgainstIR = Mode::MissingFromTBD;
    } else if (value == "all") {
      Opts.ValidateTBDAgainstIR = Mode::All;
    } else {
      Diags.diagnose(SourceLoc(), diag::error_unsupported_option_argument,
                     A->getOption().getPrefixedName(), value);
    }
  }
}

void ArgsToFrontendOptionsConverter::computeHelpOptions() {
  using namespace options;
  if (const Arg *A = Args.getLastArg(OPT_help, OPT_help_hidden)) {
    if (A->getOption().matches(OPT_help)) {
      Opts.PrintHelp = true;
    } else if (A->getOption().matches(OPT_help_hidden)) {
      Opts.PrintHelpHidden = true;
    } else {
      llvm_unreachable("Unknown help option parsed");
    }
  }
}

void ArgsToFrontendOptionsConverter::computeDumpScopeMapLocations() {
  using namespace options;
  const Arg *A = Args.getLastArg(OPT_modes_Group);
  if (!A || !A->getOption().matches(OPT_dump_scope_maps))
    return;
  StringRef value = A->getValue();
  if (value == "expanded") {
    // Note: fully expanded the scope map.
    return;
  }
  // Parse a comma-separated list of line:column for lookups to
  // perform (and dump the result of).
  SmallVector<StringRef, 4> locations;
  value.split(locations, ',');

  bool invalid = false;
  for (auto location : locations) {
    auto lineColumnStr = location.split(':');
    unsigned line, column;
    if (lineColumnStr.first.getAsInteger(10, line) ||
        lineColumnStr.second.getAsInteger(10, column)) {
      Diags.diagnose(SourceLoc(), diag::error_invalid_source_location_str,
                     location);
      invalid = true;
      continue;
    }
    Opts.DumpScopeMapLocations.push_back({line, column});
  }

  if (!invalid && Opts.DumpScopeMapLocations.empty())
    Diags.diagnose(SourceLoc(), diag::error_no_source_location_scope_map);
}

FrontendOptions::ActionType
ArgsToFrontendOptionsConverter::determineRequestedAction(const ArgList &args) {
  using namespace options;
  const Arg *A = args.getLastArg(OPT_modes_Group);
  if (!A) {
    // We don't have a mode, so determine a default.
    if (args.hasArg(OPT_emit_module, OPT_emit_module_path)) {
      // We've been told to emit a module, but have no other mode indicators.
      // As a result, put the frontend into EmitModuleOnly mode.
      // (Setting up module output will be handled below.)
      return FrontendOptions::ActionType::EmitModuleOnly;
    }

    if (args.hasArg(OPT_version))
      return FrontendOptions::ActionType::PrintVersion;

    return FrontendOptions::ActionType::NoneAction;
  }
  Option Opt = A->getOption();
  if (Opt.matches(OPT_emit_object))
    return FrontendOptions::ActionType::EmitObject;
  if (Opt.matches(OPT_emit_assembly))
    return FrontendOptions::ActionType::EmitAssembly;
  if (Opt.matches(OPT_emit_irgen))
    return FrontendOptions::ActionType::EmitIRGen;
  if (Opt.matches(OPT_emit_ir))
    return FrontendOptions::ActionType::EmitIR;
  if (Opt.matches(OPT_emit_bc))
    return FrontendOptions::ActionType::EmitBC;
  if (Opt.matches(OPT_emit_sil))
    return FrontendOptions::ActionType::EmitSIL;
  if (Opt.matches(OPT_emit_silgen))
    return FrontendOptions::ActionType::EmitSILGen;
  if (Opt.matches(OPT_emit_sib))
    return FrontendOptions::ActionType::EmitSIB;
  if (Opt.matches(OPT_emit_sibgen))
    return FrontendOptions::ActionType::EmitSIBGen;
  if (Opt.matches(OPT_emit_pch))
    return FrontendOptions::ActionType::EmitPCH;
  if (Opt.matches(OPT_emit_imported_modules))
    return FrontendOptions::ActionType::EmitImportedModules;
  if (Opt.matches(OPT_scan_dependencies))
    return FrontendOptions::ActionType::ScanDependencies;
  if (Opt.matches(OPT_parse))
    return FrontendOptions::ActionType::Parse;
  if (Opt.matches(OPT_resolve_imports))
    return FrontendOptions::ActionType::ResolveImports;
  if (Opt.matches(OPT_typecheck))
    return FrontendOptions::ActionType::Typecheck;
  if (Opt.matches(OPT_dump_parse))
    return FrontendOptions::ActionType::DumpParse;
  if (Opt.matches(OPT_dump_ast))
    return FrontendOptions::ActionType::DumpAST;
  if (Opt.matches(OPT_emit_syntax))
    return FrontendOptions::ActionType::EmitSyntax;
  if (Opt.matches(OPT_merge_modules))
    return FrontendOptions::ActionType::MergeModules;
  if (Opt.matches(OPT_dump_scope_maps))
    return FrontendOptions::ActionType::DumpScopeMaps;
  if (Opt.matches(OPT_dump_type_refinement_contexts))
    return FrontendOptions::ActionType::DumpTypeRefinementContexts;
  if (Opt.matches(OPT_dump_interface_hash))
    return FrontendOptions::ActionType::DumpInterfaceHash;
  if (Opt.matches(OPT_dump_type_info))
    return FrontendOptions::ActionType::DumpTypeInfo;
  if (Opt.matches(OPT_print_ast))
    return FrontendOptions::ActionType::PrintAST;
  if (Opt.matches(OPT_print_ast_decl))
    return FrontendOptions::ActionType::PrintASTDecl;
  if (Opt.matches(OPT_emit_pcm))
    return FrontendOptions::ActionType::EmitPCM;
  if (Opt.matches(OPT_dump_pcm))
    return FrontendOptions::ActionType::DumpPCM;

  if (Opt.matches(OPT_repl) || Opt.matches(OPT_deprecated_integrated_repl))
    return FrontendOptions::ActionType::REPL;
  if (Opt.matches(OPT_interpret))
    return FrontendOptions::ActionType::Immediate;
  if (Opt.matches(OPT_compile_module_from_interface))
    return FrontendOptions::ActionType::CompileModuleFromInterface;
  if (Opt.matches(OPT_typecheck_module_from_interface))
    return FrontendOptions::ActionType::TypecheckModuleFromInterface;
  if (Opt.matches(OPT_emit_supported_features))
    return FrontendOptions::ActionType::PrintFeature;
  llvm_unreachable("Unhandled mode option");
}

bool ArgsToFrontendOptionsConverter::setUpImmediateArgs() {
  using namespace options;
  bool treatAsSIL =
      Args.hasArg(OPT_parse_sil) || Opts.InputsAndOutputs.shouldTreatAsSIL();

  if (Opts.InputsAndOutputs.verifyInputs(
          Diags, treatAsSIL,
          Opts.RequestedAction == FrontendOptions::ActionType::REPL,
          !FrontendOptions::doesActionRequireInputs(Opts.RequestedAction))) {
    return true;
  }
  if (Opts.RequestedAction == FrontendOptions::ActionType::Immediate) {
    Opts.ImmediateArgv.push_back(
        Opts.InputsAndOutputs.getFilenameOfFirstInput()); // argv[0]
    if (const Arg *A = Args.getLastArg(OPT__DASH_DASH)) {
      for (unsigned i = 0, e = A->getNumValues(); i != e; ++i) {
        Opts.ImmediateArgv.push_back(A->getValue(i));
      }
    }
  }

  return false;
}

bool ArgsToFrontendOptionsConverter::computeModuleAliases() {
  auto list = Args.getAllArgValues(options::OPT_module_alias);
  return ModuleAliasesConverter::computeModuleAliases(list, Opts, Diags);
}

bool ArgsToFrontendOptionsConverter::computeModuleName() {
  // Module name must be computed before computing module
  // aliases. Instead of asserting, clearing ModuleAliasMap
  // here since it can be called redundantly in batch-mode
  Opts.ModuleAliasMap.clear();

  const Arg *A = Args.getLastArg(options::OPT_module_name);
  if (A) {
    Opts.ModuleName = A->getValue();
  } else if (Opts.ModuleName.empty()) {
    // The user did not specify a module name, so determine a default fallback
    // based on other options.

    // Note: this code path will only be taken when running the frontend
    // directly; the driver should always pass -module-name when invoking the
    // frontend.
    if (computeFallbackModuleName())
      return true;
  }

  if (Lexer::isIdentifier(Opts.ModuleName) &&
      (Opts.ModuleName != STDLIB_NAME || Opts.ParseStdlib)) {
    return false;
  }
  if (!FrontendOptions::needsProperModuleName(Opts.RequestedAction) ||
      Opts.isCompilingExactlyOneSwiftFile()) {
    Opts.ModuleName = "main";
    return false;
  }
  auto DID = (Opts.ModuleName == STDLIB_NAME) ? diag::error_stdlib_module_name
                                              : diag::error_bad_module_name;
  Diags.diagnose(SourceLoc(), DID, Opts.ModuleName, A == nullptr);
  Opts.ModuleName = "__bad__";
  return false; // FIXME: Must continue to run to pass the tests, but should not
  // have to.
}

bool ArgsToFrontendOptionsConverter::computeFallbackModuleName() {
  if (Opts.RequestedAction == FrontendOptions::ActionType::REPL) {
    // Default to a module named "REPL" if we're in REPL mode.
    Opts.ModuleName = "REPL";
    return false;
  }
  // In order to pass some tests, must leave ModuleName empty.
  if (!Opts.InputsAndOutputs.hasInputs()) {
    Opts.ModuleName = std::string();
    // FIXME: This is a bug that should not happen, but does in tests.
    // The compiler should bail out earlier, where "no frontend action was
    // selected".
    return false;
  }
  Optional<std::vector<std::string>> outputFilenames =
      OutputFilesComputer::getOutputFilenamesFromCommandLineOrFilelist(
        Args, Diags, options::OPT_o, options::OPT_output_filelist);

  std::string nameToStem =
      outputFilenames && outputFilenames->size() == 1 &&
              outputFilenames->front() != "-" &&
              !llvm::sys::fs::is_directory(outputFilenames->front())
          ? outputFilenames->front()
          : Opts.InputsAndOutputs.getFilenameOfFirstInput();

  Opts.ModuleName = llvm::sys::path::stem(nameToStem).str();
  return false;
}

bool ArgsToFrontendOptionsConverter::
    computeMainAndSupplementaryOutputFilenames() {
  std::vector<std::string> mainOutputs;
  std::vector<std::string> mainOutputForIndexUnits;
  std::vector<SupplementaryOutputPaths> supplementaryOutputs;
  const bool hadError = ArgsToFrontendOutputsConverter(
                            Args, Opts.ModuleName, Opts.InputsAndOutputs, Diags)
                            .convert(mainOutputs, mainOutputForIndexUnits,
                                     supplementaryOutputs);
  if (hadError)
    return true;
  Opts.InputsAndOutputs.setMainAndSupplementaryOutputs(mainOutputs,
                                                       supplementaryOutputs,
                                                       mainOutputForIndexUnits);
  return false;
}

bool ArgsToFrontendOptionsConverter::checkBuildFromInterfaceOnlyOptions()
    const {
  if (Opts.RequestedAction != FrontendOptions::ActionType::CompileModuleFromInterface &&
      Opts.ExplicitInterfaceBuild) {
    Diags.diagnose(SourceLoc(),
                   diag::error_cannot_explicit_interface_build_in_mode);
    return true;
  }
  return false;
}

bool ArgsToFrontendOptionsConverter::checkUnusedSupplementaryOutputPaths()
    const {
  if (!FrontendOptions::canActionEmitDependencies(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasDependenciesPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_dependencies);
    return true;
  }
  if (!FrontendOptions::canActionEmitReferenceDependencies(Opts.RequestedAction)
      && Opts.InputsAndOutputs.hasReferenceDependenciesPath()) {
    Diags.diagnose(SourceLoc(),
                   diag::error_mode_cannot_emit_reference_dependencies);
    return true;
  }
  if (!FrontendOptions::canActionEmitClangHeader(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasClangHeaderOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_header);
    return true;
  }
  if (!FrontendOptions::canActionEmitLoadedModuleTrace(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasLoadedModuleTracePath()) {
    Diags.diagnose(SourceLoc(),
                   diag::error_mode_cannot_emit_loaded_module_trace);
    return true;
  }
  if (!FrontendOptions::canActionEmitModule(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasModuleOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_module);
    return true;
  }
  if (!FrontendOptions::canActionEmitModuleDoc(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasModuleDocOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_module_doc);
    return true;
  }
  if (!FrontendOptions::canActionEmitABIDescriptor(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasABIDescriptorOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_abi_descriptor);
    return true;
  }
  if (!FrontendOptions::canActionEmitConstValues(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasConstValuesOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_const_values);
    return true;
  }
  if (!FrontendOptions::canActionEmitModuleSemanticInfo(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasModuleSemanticInfoOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_module_semantic_info);
    return true;
  }
  // If we cannot emit module doc, we cannot emit source information file either.
  if (!FrontendOptions::canActionEmitModuleDoc(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasModuleSourceInfoOutputPath()) {
     Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_module_source_info);
     return true;
   }
  if (!FrontendOptions::canActionEmitInterface(Opts.RequestedAction) &&
      (Opts.InputsAndOutputs.hasModuleInterfaceOutputPath() ||
       Opts.InputsAndOutputs.hasPrivateModuleInterfaceOutputPath())) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_interface);
    return true;
  }
  if (!FrontendOptions::canActionEmitModuleSummary(Opts.RequestedAction) &&
      Opts.InputsAndOutputs.hasModuleSummaryOutputPath()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_module_summary);
    return true;
  }
  if (!FrontendOptions::canActionEmitModule(Opts.RequestedAction) &&
      !Opts.SymbolGraphOutputDir.empty()) {
    Diags.diagnose(SourceLoc(), diag::error_mode_cannot_emit_symbol_graph);
    return true;
  }
  return false;
}

void ArgsToFrontendOptionsConverter::computeImportObjCHeaderOptions() {
  using namespace options;
  if (const Arg *A = Args.getLastArgNoClaim(OPT_import_objc_header)) {
    Opts.ImplicitObjCHeaderPath = A->getValue();
    Opts.SerializeBridgingHeader |= !Opts.InputsAndOutputs.hasPrimaryInputs();
  }
}
void ArgsToFrontendOptionsConverter::
computeImplicitImportModuleNames(OptSpecifier id, bool isTestable) {
  using namespace options;
  for (const Arg *A : Args.filtered(id)) {
    auto *moduleStr = A->getValue();
    if (!Lexer::isIdentifier(moduleStr)) {
      Diags.diagnose(SourceLoc(), diag::error_bad_module_name, moduleStr,
                     /*suggestModuleNameFlag*/ false);
      continue;
    }
    Opts.ImplicitImportModuleNames.emplace_back(moduleStr, isTestable);
  }
}
void ArgsToFrontendOptionsConverter::computeLLVMArgs() {
  using namespace options;
  for (const Arg *A : Args.filtered(OPT_Xllvm)) {
    Opts.LLVMArgs.push_back(A->getValue());
  }
}

bool ModuleAliasesConverter::computeModuleAliases(std::vector<std::string> args,
                                                  FrontendOptions &options,
                                                  DiagnosticEngine &diags) {
  if (!args.empty()) {
    // ModuleAliasMap should initially be empty as setting
    // it should be called only once
    options.ModuleAliasMap.clear();
    
    auto validate = [&options, &diags](StringRef value, bool allowModuleName) -> bool
    {
      if (!allowModuleName) {
        if (value == options.ModuleName ||
            value == options.ModuleABIName ||
            value == options.ModuleLinkName ||
            value == STDLIB_NAME) {
          diags.diagnose(SourceLoc(), diag::error_module_alias_forbidden_name, value);
          return false;
        }
      }
      if (!Lexer::isIdentifier(value)) {
        diags.diagnose(SourceLoc(), diag::error_bad_module_name, value, false);
        return false;
      }
      return true;
    };
    
    for (auto item: args) {
      auto str = StringRef(item);
      // splits to an alias and the underlying name
      auto pair = str.split('=');
      auto lhs = pair.first;
      auto rhs = pair.second;
      
      if (rhs.empty()) { // '=' is missing
        diags.diagnose(SourceLoc(), diag::error_module_alias_invalid_format, str);
        return false;
      }
      if (!validate(lhs, false) || !validate(rhs, true)) {
        return false;
      }
      
      // First, add the underlying name as a key to prevent it from being
      // used as an alias
      if (!options.ModuleAliasMap.insert({rhs, StringRef()}).second) {
        diags.diagnose(SourceLoc(), diag::error_module_alias_duplicate, rhs);
        return false;
      }
      // Next, add the alias as a key and the underlying name as a value to the map
      auto underlyingName = options.ModuleAliasMap.find(rhs)->first();
      if (!options.ModuleAliasMap.insert({lhs, underlyingName}).second) {
        diags.diagnose(SourceLoc(), diag::error_module_alias_duplicate, lhs);
        return false;
      }
    }
  }
  return true;
}