// Copyright (c) 2018-2019, NVIDIA CORPORATION.  All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Generates Fortran from the content of a parse tree, using the
// traversal templates in parse-tree-visitor.h.

#include "unparse.h"
#include "characters.h"
#include "parse-tree-visitor.h"
#include "parse-tree.h"
#include "../common/Fortran.h"
#include "../common/idioms.h"
#include "../common/indirection.h"
#include <algorithm>
#include <cinttypes>
#include <cstddef>
#include <set>

namespace Fortran::parser {

class UnparseVisitor {
public:
  UnparseVisitor(std::ostream &out, int indentationAmount, Encoding encoding,
      bool capitalize, bool backslashEscapes, preStatementType *preStatement)
    : out_{out}, indentationAmount_{indentationAmount}, encoding_{encoding},
      capitalizeKeywords_{capitalize}, backslashEscapes_{backslashEscapes},
      preStatement_{preStatement} {}

  // In nearly all cases, this code avoids defining Boolean-valued Pre()
  // callbacks for the parse tree walking framework in favor of two void
  // functions, Before() and Unparse(), which imply true and false return
  // values for Pre() respectively.
  template<typename T> void Before(const T &) {}
  template<typename T> double Unparse(const T &);  // not void, never used

  template<typename T> bool Pre(const T &x) {
    if constexpr (std::is_void_v<decltype(Unparse(x))>) {
      // There is a local definition of Unparse() for this type.  It
      // overrides the parse tree walker's default Walk() over the descendents.
      Before(x);
      Unparse(x);
      Post(x);
      return false;  // Walk() does not visit descendents
    } else {
      Before(x);
      return true;  // there's no Unparse() defined here, Walk() the descendents
    }
  }
  template<typename T> void Post(const T &) {}

  // Emit simple types as-is.
  void Unparse(const std::string &x) { Put(x); }
  void Unparse(int x) { Put(std::to_string(x)); }
  void Unparse(unsigned int x) { Put(std::to_string(x)); }
  void Unparse(long x) { Put(std::to_string(x)); }
  void Unparse(unsigned long x) { Put(std::to_string(x)); }
  void Unparse(long long x) { Put(std::to_string(x)); }
  void Unparse(unsigned long long x) { Put(std::to_string(x)); }
  void Unparse(char x) { Put(x); }

  // Statement labels and ends of lines
  template<typename T> void Before(const Statement<T> &x) {
    if (preStatement_) {
      (*preStatement_)(x.source, out_, indent_);
    }
    Walk(x.label, " ");
  }
  template<typename T> void Post(const Statement<T> &) { Put('\n'); }

  // The special-case formatting functions for these productions are
  // ordered to correspond roughly to their order of appearance in
  // the Fortran 2018 standard (and parse-tree.h).

  void Unparse(const Program &x) {  // R501
    Walk("", x.v, "\n");  // put blank lines between ProgramUnits
  }

  void Unparse(const Name &x) {  // R603
    Put(x.ToString());
  }
  void Unparse(const DefinedOperator::IntrinsicOperator &x) {  // R608
    switch (x) {
    case DefinedOperator::IntrinsicOperator::Power: Put("**"); break;
    case DefinedOperator::IntrinsicOperator::Multiply: Put('*'); break;
    case DefinedOperator::IntrinsicOperator::Divide: Put('/'); break;
    case DefinedOperator::IntrinsicOperator::Add: Put('+'); break;
    case DefinedOperator::IntrinsicOperator::Subtract: Put('-'); break;
    case DefinedOperator::IntrinsicOperator::Concat: Put("//"); break;
    case DefinedOperator::IntrinsicOperator::LT: Put('<'); break;
    case DefinedOperator::IntrinsicOperator::LE: Put("<="); break;
    case DefinedOperator::IntrinsicOperator::EQ: Put("=="); break;
    case DefinedOperator::IntrinsicOperator::NE: Put("/="); break;
    case DefinedOperator::IntrinsicOperator::GE: Put(">="); break;
    case DefinedOperator::IntrinsicOperator::GT: Put('>'); break;
    default: Put('.'), Word(DefinedOperator::EnumToString(x)), Put('.');
    }
  }
  void Post(const Star &) { Put('*'); }  // R701 &c.
  void Post(const TypeParamValue::Deferred &) { Put(':'); }  // R701
  void Unparse(const DeclarationTypeSpec::Type &x) {  // R703
    Word("TYPE("), Walk(x.derived), Put(')');
  }
  void Unparse(const DeclarationTypeSpec::Class &x) {
    Word("CLASS("), Walk(x.derived), Put(')');
  }
  void Post(const DeclarationTypeSpec::ClassStar &) { Word("CLASS(*)"); }
  void Post(const DeclarationTypeSpec::TypeStar &) { Word("TYPE(*)"); }
  void Unparse(const DeclarationTypeSpec::Record &x) {
    Word("RECORD/"), Walk(x.v), Put('/');
  }
  void Before(const IntrinsicTypeSpec::Real &x) {  // R704
    Word("REAL");
  }
  void Before(const IntrinsicTypeSpec::Complex &x) { Word("COMPLEX"); }
  void Post(const IntrinsicTypeSpec::DoublePrecision &) {
    Word("DOUBLE PRECISION");
  }
  void Before(const IntrinsicTypeSpec::Character &x) { Word("CHARACTER"); }
  void Before(const IntrinsicTypeSpec::Logical &x) { Word("LOGICAL"); }
  void Post(const IntrinsicTypeSpec::DoubleComplex &) {
    Word("DOUBLE COMPLEX");
  }
  void Before(const IntrinsicTypeSpec::NCharacter &x) { Word("NCHARACTER"); }
  void Before(const IntegerTypeSpec &x) {  // R705
    Word("INTEGER");
  }
  void Unparse(const KindSelector &x) {  // R706
    std::visit(
        common::visitors{
            [&](const ScalarIntConstantExpr &y) {
              Put('('), Word("KIND="), Walk(y), Put(')');
            },
            [&](const KindSelector::StarSize &y) { Put('*'), Walk(y.v); },
        },
        x.u);
  }
  void Unparse(const SignedIntLiteralConstant &x) {  // R707
    Walk(std::get<std::int64_t>(x.t));
    Walk("_", std::get<std::optional<KindParam>>(x.t));
  }
  void Unparse(const IntLiteralConstant &x) {  // R708
    Walk(std::get<std::uint64_t>(x.t));
    Walk("_", std::get<std::optional<KindParam>>(x.t));
  }
  void Unparse(const Sign &x) {  // R712
    Put(x == Sign::Negative ? '-' : '+');
  }
  void Unparse(const RealLiteralConstant &x) {  // R714, R715
    Put(x.real.source.ToString()), Walk("_", x.kind);
  }
  void Unparse(const ComplexLiteralConstant &x) {  // R718 - R720
    Put('('), Walk(x.t, ","), Put(')');
  }
  void Unparse(const CharSelector::LengthAndKind &x) {  // R721
    Put('('), Word("KIND="), Walk(x.kind);
    Walk(", LEN=", x.length), Put(')');
  }
  void Unparse(const LengthSelector &x) {  // R722
    std::visit(
        common::visitors{
            [&](const TypeParamValue &y) {
              Put('('), Word("LEN="), Walk(y), Put(')');
            },
            [&](const CharLength &y) { Put('*'), Walk(y); },
        },
        x.u);
  }
  void Unparse(const CharLength &x) {  // R723
    std::visit(
        common::visitors{
            [&](const TypeParamValue &y) { Put('('), Walk(y), Put(')'); },
            [&](const std::int64_t &y) { Walk(y); },
        },
        x.u);
  }
  void Unparse(const CharLiteralConstant &x) {  // R724
    if (const auto &k{std::get<std::optional<KindParam>>(x.t)}) {
      if (std::holds_alternative<KindParam::Kanji>(k->u)) {
        Word("NC");
      } else {
        Walk(*k), Put('_');
      }
    }
    Put(QuoteCharacterLiteral(
        std::get<std::string>(x.t), true, backslashEscapes_));
  }
  void Before(const HollerithLiteralConstant &x) {
    std::optional<std::size_t> chars{CountCharacters(x.v.data(), x.v.size(),
        encoding_ == Encoding::EUC_JP ? EUC_JPCharacterBytes
                                      : UTF8CharacterBytes)};
    if (chars.has_value()) {
      Unparse(*chars);
    } else {
      Unparse(x.v.size());
    }
    Put('H');
  }
  void Unparse(const LogicalLiteralConstant &x) {  // R725
    Put(std::get<bool>(x.t) ? ".TRUE." : ".FALSE.");
    Walk("_", std::get<std::optional<KindParam>>(x.t));
  }
  void Unparse(const DerivedTypeStmt &x) {  // R727
    Word("TYPE"), Walk(", ", std::get<std::list<TypeAttrSpec>>(x.t), ", ");
    Put(" :: "), Walk(std::get<Name>(x.t));
    Walk("(", std::get<std::list<Name>>(x.t), ", ", ")");
    Indent();
  }
  void Unparse(const Abstract &x) {  // R728, &c.
    Word("ABSTRACT");
  }
  void Post(const TypeAttrSpec::BindC &) { Word("BIND(C)"); }
  void Unparse(const TypeAttrSpec::Extends &x) {
    Word("EXTENDS("), Walk(x.v), Put(')');
  }
  void Unparse(const EndTypeStmt &x) {  // R730
    Outdent(), Word("END TYPE"), Walk(" ", x.v);
  }
  void Unparse(const SequenceStmt &x) {  // R731
    Word("SEQUENCE");
  }
  void Unparse(const TypeParamDefStmt &x) {  // R732
    Walk(std::get<IntegerTypeSpec>(x.t));
    Put(", "), Walk(std::get<common::TypeParamAttr>(x.t));
    Put(" :: "), Walk(std::get<std::list<TypeParamDecl>>(x.t), ", ");
  }
  void Unparse(const TypeParamDecl &x) {  // R733
    Walk(std::get<Name>(x.t));
    Walk("=", std::get<std::optional<ScalarIntConstantExpr>>(x.t));
  }
  void Unparse(const DataComponentDefStmt &x) {  // R737
    const auto &dts{std::get<DeclarationTypeSpec>(x.t)};
    const auto &attrs{std::get<std::list<ComponentAttrSpec>>(x.t)};
    const auto &decls{std::get<std::list<ComponentDecl>>(x.t)};
    Walk(dts), Walk(", ", attrs, ", ");
    if (!attrs.empty() ||
        (!std::holds_alternative<DeclarationTypeSpec::Record>(dts.u) &&
            std::none_of(
                decls.begin(), decls.end(), [](const ComponentDecl &d) {
                  const auto &init{
                      std::get<std::optional<Initialization>>(d.t)};
                  return init.has_value() &&
                      std::holds_alternative<
                          std::list<common::Indirection<DataStmtValue>>>(
                          init->u);
                }))) {
      Put(" ::");
    }
    Put(' '), Walk(decls, ", ");
  }
  void Unparse(const Allocatable &x) {  // R738
    Word("ALLOCATABLE");
  }
  void Unparse(const Pointer &x) { Word("POINTER"); }
  void Unparse(const Contiguous &x) { Word("CONTIGUOUS"); }
  void Before(const ComponentAttrSpec &x) {
    std::visit(
        common::visitors{
            [&](const CoarraySpec &) { Word("CODIMENSION["); },
            [&](const ComponentArraySpec &) { Word("DIMENSION("); },
            [](const auto &) {},
        },
        x.u);
  }
  void Post(const ComponentAttrSpec &x) {
    std::visit(
        common::visitors{
            [&](const CoarraySpec &) { Put(']'); },
            [&](const ComponentArraySpec &) { Put(')'); },
            [](const auto &) {},
        },
        x.u);
  }
  void Unparse(const ComponentDecl &x) {  // R739
    Walk(std::get<ObjectName>(x.t));
    Walk("(", std::get<std::optional<ComponentArraySpec>>(x.t), ")");
    Walk("[", std::get<std::optional<CoarraySpec>>(x.t), "]");
    Walk("*", std::get<std::optional<CharLength>>(x.t));
    Walk(std::get<std::optional<Initialization>>(x.t));
  }
  void Unparse(const ComponentArraySpec &x) {  // R740
    std::visit(
        common::visitors{
            [&](const std::list<ExplicitShapeSpec> &y) { Walk(y, ","); },
            [&](const DeferredShapeSpecList &y) { Walk(y); },
        },
        x.u);
  }
  void Unparse(const ProcComponentDefStmt &x) {  // R741
    Word("PROCEDURE(");
    Walk(std::get<std::optional<ProcInterface>>(x.t)), Put(')');
    Walk(", ", std::get<std::list<ProcComponentAttrSpec>>(x.t), ", ");
    Put(" :: "), Walk(std::get<std::list<ProcDecl>>(x.t), ", ");
  }
  void Unparse(const NoPass &x) {  // R742
    Word("NOPASS");
  }
  void Unparse(const Pass &x) { Word("PASS"), Walk("(", x.v, ")"); }
  void Unparse(const Initialization &x) {  // R743 & R805
    std::visit(
        common::visitors{
            [&](const ConstantExpr &y) { Put(" = "), Walk(y); },
            [&](const NullInit &y) { Put(" => "), Walk(y); },
            [&](const InitialDataTarget &y) { Put(" => "), Walk(y); },
            [&](const std::list<common::Indirection<DataStmtValue>> &y) {
              Walk("/", y, ", ", "/");
            },
        },
        x.u);
  }
  void Unparse(const PrivateStmt &x) {  // R745
    Word("PRIVATE");
  }
  void Unparse(const TypeBoundProcedureStmt::WithoutInterface &x) {  // R749
    Word("PROCEDURE"), Walk(", ", x.attributes, ", ");
    Put(" :: "), Walk(x.declarations, ", ");
  }
  void Unparse(const TypeBoundProcedureStmt::WithInterface &x) {
    Word("PROCEDURE("), Walk(x.interfaceName), Put("), ");
    Walk(x.attributes);
    Put(" :: "), Walk(x.bindingNames, ", ");
  }
  void Unparse(const TypeBoundProcDecl &x) {  // R750
    Walk(std::get<Name>(x.t));
    Walk(" => ", std::get<std::optional<Name>>(x.t));
  }
  void Unparse(const TypeBoundGenericStmt &x) {  // R751
    Word("GENERIC"), Walk(", ", std::get<std::optional<AccessSpec>>(x.t));
    Put(" :: "), Walk(std::get<common::Indirection<GenericSpec>>(x.t));
    Put(" => "), Walk(std::get<std::list<Name>>(x.t), ", ");
  }
  void Post(const BindAttr::Deferred &) { Word("DEFERRED"); }  // R752
  void Post(const BindAttr::Non_Overridable &) { Word("NON_OVERRIDABLE"); }
  void Unparse(const FinalProcedureStmt &x) {  // R753
    Word("FINAL :: "), Walk(x.v, ", ");
  }
  void Unparse(const DerivedTypeSpec &x) {  // R754
    Walk(std::get<Name>(x.t));
    Walk("(", std::get<std::list<TypeParamSpec>>(x.t), ",", ")");
  }
  void Unparse(const TypeParamSpec &x) {  // R755
    Walk(std::get<std::optional<Keyword>>(x.t), "=");
    Walk(std::get<TypeParamValue>(x.t));
  }
  void Unparse(const StructureConstructor &x) {  // R756
    Walk(std::get<DerivedTypeSpec>(x.t));
    Put('('), Walk(std::get<std::list<ComponentSpec>>(x.t), ", "), Put(')');
  }
  void Unparse(const ComponentSpec &x) {  // R757
    Walk(std::get<std::optional<Keyword>>(x.t), "=");
    Walk(std::get<ComponentDataSource>(x.t));
  }
  void Unparse(const EnumDefStmt &) {  // R760
    Word("ENUM, BIND(C)"), Indent();
  }
  void Unparse(const EnumeratorDefStmt &x) {  // R761
    Word("ENUMERATOR :: "), Walk(x.v, ", ");
  }
  void Unparse(const Enumerator &x) {  // R762
    Walk(std::get<NamedConstant>(x.t));
    Walk(" = ", std::get<std::optional<ScalarIntConstantExpr>>(x.t));
  }
  void Post(const EndEnumStmt &) {  // R763
    Outdent(), Word("END ENUM");
  }
  void Unparse(const BOZLiteralConstant &x) {  // R764 - R767
    Put(x.v);
  }
  void Unparse(const AcValue::Triplet &x) {  // R773
    Walk(std::get<0>(x.t)), Put(':'), Walk(std::get<1>(x.t));
    Walk(":", std::get<std::optional<ScalarIntExpr>>(x.t));
  }
  void Unparse(const ArrayConstructor &x) {  // R769
    Put('['), Walk(x.v), Put(']');
  }
  void Unparse(const AcSpec &x) {  // R770
    Walk(x.type, "::"), Walk(x.values, ", ");
  }
  template<typename A> void Unparse(const LoopBounds<A> &x) {
    Walk(x.name), Put('='), Walk(x.lower), Put(','), Walk(x.upper);
    Walk(",", x.step);
  }
  void Unparse(const AcImpliedDo &x) {  // R774
    Put('('), Walk(std::get<std::list<AcValue>>(x.t), ", ");
    Put(", "), Walk(std::get<AcImpliedDoControl>(x.t)), Put(')');
  }
  void Unparse(const AcImpliedDoControl &x) {  // R775
    Walk(std::get<std::optional<IntegerTypeSpec>>(x.t), "::");
    Walk(std::get<LoopBounds<ScalarIntExpr>>(x.t));
  }

  void Unparse(const TypeDeclarationStmt &x) {  // R801
    const auto &dts{std::get<DeclarationTypeSpec>(x.t)};
    const auto &attrs{std::get<std::list<AttrSpec>>(x.t)};
    const auto &decls{std::get<std::list<EntityDecl>>(x.t)};
    Walk(dts), Walk(", ", attrs, ", ");

    static const auto isInitializerOldStyle{[](const Initialization &i) {
      return std::holds_alternative<
          std::list<common::Indirection<DataStmtValue>>>(i.u);
    }};
    static const auto hasAssignmentInitializer{[](const EntityDecl &d) {
      // Does a declaration have a new-style =x initializer?
      const auto &init{std::get<std::optional<Initialization>>(d.t)};
      return init.has_value() && !isInitializerOldStyle(*init);
    }};
    static const auto hasSlashDelimitedInitializer{[](const EntityDecl &d) {
      // Does a declaration have an old-style /x/ initializer?
      const auto &init{std::get<std::optional<Initialization>>(d.t)};
      return init.has_value() && isInitializerOldStyle(*init);
    }};
    const auto useDoubledColons{[&]() {
      bool isRecord{std::holds_alternative<DeclarationTypeSpec::Record>(dts.u)};
      if (!attrs.empty()) {
        // Attributes after the type require :: before the entities.
        CHECK(!isRecord);
        return true;
      }
      if (std::any_of(decls.begin(), decls.end(), hasAssignmentInitializer)) {
        // Always use :: with new style standard initializers (=x),
        // since the standard requires them to appear (even in free form,
        // where mandatory spaces already disambiguate INTEGER J=666).
        CHECK(!isRecord);
        return true;
      }
      if (isRecord) {
        // Never put :: in a legacy extension RECORD// statement.
        return false;
      }
      // The :: is optional for this declaration.  Avoid usage that can
      // crash the pgf90 compiler.
      if (std::any_of(
              decls.begin(), decls.end(), hasSlashDelimitedInitializer)) {
        // Don't use :: when a declaration uses legacy DATA-statement-like
        // /x/ initialization.
        return false;
      }
      // Don't use :: with intrinsic types.  Otherwise, use it.
      return !std::holds_alternative<IntrinsicTypeSpec>(dts.u);
    }};

    if (useDoubledColons()) {
      Put(" ::");
    }
    Put(' '), Walk(std::get<std::list<EntityDecl>>(x.t), ", ");
  }
  void Before(const AttrSpec &x) {  // R802
    std::visit(
        common::visitors{
            [&](const CoarraySpec &y) { Word("CODIMENSION["); },
            [&](const ArraySpec &y) { Word("DIMENSION("); },
            [](const auto &) {},
        },
        x.u);
  }
  void Post(const AttrSpec &x) {
    std::visit(
        common::visitors{
            [&](const CoarraySpec &y) { Put(']'); },
            [&](const ArraySpec &y) { Put(')'); },
            [](const auto &) {},
        },
        x.u);
  }
  void Unparse(const EntityDecl &x) {  // R803
    Walk(std::get<ObjectName>(x.t));
    Walk("(", std::get<std::optional<ArraySpec>>(x.t), ")");
    Walk("[", std::get<std::optional<CoarraySpec>>(x.t), "]");
    Walk("*", std::get<std::optional<CharLength>>(x.t));
    Walk(std::get<std::optional<Initialization>>(x.t));
  }
  void Unparse(const NullInit &x) {  // R806
    Word("NULL()");
  }
  void Unparse(const LanguageBindingSpec &x) {  // R808 & R1528
    Word("BIND(C"), Walk(", NAME=", x.v), Put(')');
  }
  void Unparse(const CoarraySpec &x) {  // R809
    std::visit(
        common::visitors{
            [&](const DeferredCoshapeSpecList &y) { Walk(y); },
            [&](const ExplicitCoshapeSpec &y) { Walk(y); },
        },
        x.u);
  }
  void Unparse(const DeferredCoshapeSpecList &x) {  // R810
    for (auto j{x.v}; j > 0; --j) {
      Put(':');
      if (j > 1) {
        Put(',');
      }
    }
  }
  void Unparse(const ExplicitCoshapeSpec &x) {  // R811
    Walk(std::get<std::list<ExplicitShapeSpec>>(x.t), ",", ",");
    Walk(std::get<std::optional<SpecificationExpr>>(x.t), ":"), Put('*');
  }
  void Unparse(const ExplicitShapeSpec &x) {  // R812 - R813 & R816 - R818
    Walk(std::get<std::optional<SpecificationExpr>>(x.t), ":");
    Walk(std::get<SpecificationExpr>(x.t));
  }
  void Unparse(const ArraySpec &x) {  // R815
    std::visit(
        common::visitors{
            [&](const std::list<ExplicitShapeSpec> &y) { Walk(y, ","); },
            [&](const std::list<AssumedShapeSpec> &y) { Walk(y, ","); },
            [&](const DeferredShapeSpecList &y) { Walk(y); },
            [&](const AssumedSizeSpec &y) { Walk(y); },
            [&](const ImpliedShapeSpec &y) { Walk(y); },
            [&](const AssumedRankSpec &y) { Walk(y); },
        },
        x.u);
  }
  void Post(const AssumedShapeSpec &) { Put(':'); }  // R819
  void Unparse(const DeferredShapeSpecList &x) {  // R820
    for (auto j{x.v}; j > 0; --j) {
      Put(':');
      if (j > 1) {
        Put(',');
      }
    }
  }
  void Unparse(const AssumedImpliedSpec &x) {  // R821
    Walk(x.v, ":");
    Put('*');
  }
  void Unparse(const AssumedSizeSpec &x) {  // R822
    Walk(std::get<std::list<ExplicitShapeSpec>>(x.t), ",", ",");
    Walk(std::get<AssumedImpliedSpec>(x.t));
  }
  void Unparse(const ImpliedShapeSpec &x) {  // R823
    Walk(x.v, ",");
  }
  void Post(const AssumedRankSpec &) { Put(".."); }  // R825
  void Post(const Asynchronous &) { Word("ASYNCHRONOUS"); }
  void Post(const External &) { Word("EXTERNAL"); }
  void Post(const Intrinsic &) { Word("INTRINSIC"); }
  void Post(const Optional &) { Word("OPTIONAL"); }
  void Post(const Parameter &) { Word("PARAMETER"); }
  void Post(const Protected &) { Word("PROTECTED"); }
  void Post(const Save &) { Word("SAVE"); }
  void Post(const Target &) { Word("TARGET"); }
  void Post(const Value &) { Word("VALUE"); }
  void Post(const Volatile &) { Word("VOLATILE"); }
  void Unparse(const IntentSpec &x) {  // R826
    Word("INTENT("), Walk(x.v), Put(")");
  }
  void Unparse(const AccessStmt &x) {  // R827
    Walk(std::get<AccessSpec>(x.t));
    Walk(" :: ", std::get<std::list<AccessId>>(x.t), ", ");
  }
  void Unparse(const AllocatableStmt &x) {  // R829
    Word("ALLOCATABLE :: "), Walk(x.v, ", ");
  }
  void Unparse(const ObjectDecl &x) {  // R830 & R860
    Walk(std::get<ObjectName>(x.t));
    Walk("(", std::get<std::optional<ArraySpec>>(x.t), ")");
    Walk("[", std::get<std::optional<CoarraySpec>>(x.t), "]");
  }
  void Unparse(const AsynchronousStmt &x) {  // R831
    Word("ASYNCHRONOUS :: "), Walk(x.v, ", ");
  }
  void Unparse(const BindStmt &x) {  // R832
    Walk(x.t, " :: ");
  }
  void Unparse(const BindEntity &x) {  // R833
    bool isCommon{std::get<BindEntity::Kind>(x.t) == BindEntity::Kind::Common};
    const char *slash{isCommon ? "/" : ""};
    Put(slash), Walk(std::get<Name>(x.t)), Put(slash);
  }
  void Unparse(const CodimensionStmt &x) {  // R834
    Word("CODIMENSION :: "), Walk(x.v, ", ");
  }
  void Unparse(const CodimensionDecl &x) {  // R835
    Walk(std::get<Name>(x.t));
    Put('['), Walk(std::get<CoarraySpec>(x.t)), Put(']');
  }
  void Unparse(const ContiguousStmt &x) {  // R836
    Word("CONTIGUOUS :: "), Walk(x.v, ", ");
  }
  void Unparse(const DataStmt &x) {  // R837
    Word("DATA "), Walk(x.v, ", ");
  }
  void Unparse(const DataStmtSet &x) {  // R838
    Walk(std::get<std::list<DataStmtObject>>(x.t), ", ");
    Put('/'), Walk(std::get<std::list<DataStmtValue>>(x.t), ", "), Put('/');
  }
  void Unparse(const DataImpliedDo &x) {  // R840, R842
    Put('('), Walk(std::get<std::list<DataIDoObject>>(x.t), ", "), Put(',');
    Walk(std::get<std::optional<IntegerTypeSpec>>(x.t), "::");
    Walk(std::get<LoopBounds<ScalarIntConstantExpr>>(x.t)), Put(')');
  }
  void Unparse(const DataStmtValue &x) {  // R843
    Walk(std::get<std::optional<DataStmtRepeat>>(x.t), "*");
    Walk(std::get<DataStmtConstant>(x.t));
  }
  void Unparse(const DimensionStmt &x) {  // R848
    Word("DIMENSION :: "), Walk(x.v, ", ");
  }
  void Unparse(const DimensionStmt::Declaration &x) {
    Walk(std::get<Name>(x.t));
    Put('('), Walk(std::get<ArraySpec>(x.t)), Put(')');
  }
  void Unparse(const IntentStmt &x) {  // R849
    Walk(x.t, " :: ");
  }
  void Unparse(const OptionalStmt &x) {  // R850
    Word("OPTIONAL :: "), Walk(x.v, ", ");
  }
  void Unparse(const ParameterStmt &x) {  // R851
    Word("PARAMETER("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const NamedConstantDef &x) {  // R852
    Walk(x.t, "=");
  }
  void Unparse(const PointerStmt &x) {  // R853
    Word("POINTER :: "), Walk(x.v, ", ");
  }
  void Unparse(const PointerDecl &x) {  // R854
    Walk(std::get<Name>(x.t));
    Walk("(", std::get<std::optional<DeferredShapeSpecList>>(x.t), ")");
  }
  void Unparse(const ProtectedStmt &x) {  // R855
    Word("PROTECTED :: "), Walk(x.v, ", ");
  }
  void Unparse(const SaveStmt &x) {  // R856
    Word("SAVE"), Walk(" :: ", x.v, ", ");
  }
  void Unparse(const SavedEntity &x) {  // R857, R858
    bool isCommon{
        std::get<SavedEntity::Kind>(x.t) == SavedEntity::Kind::Common};
    const char *slash{isCommon ? "/" : ""};
    Put(slash), Walk(std::get<Name>(x.t)), Put(slash);
  }
  void Unparse(const TargetStmt &x) {  // R859
    Word("TARGET :: "), Walk(x.v, ", ");
  }
  void Unparse(const ValueStmt &x) {  // R861
    Word("VALUE :: "), Walk(x.v, ", ");
  }
  void Unparse(const VolatileStmt &x) {  // R862
    Word("VOLATILE :: "), Walk(x.v, ", ");
  }
  void Unparse(const ImplicitStmt &x) {  // R863
    Word("IMPLICIT ");
    std::visit(
        common::visitors{
            [&](const std::list<ImplicitSpec> &y) { Walk(y, ", "); },
            [&](const std::list<ImplicitStmt::ImplicitNoneNameSpec> &y) {
              Word("NONE"), Walk(" (", y, ", ", ")");
            },
        },
        x.u);
  }
  void Unparse(const ImplicitSpec &x) {  // R864
    Walk(std::get<DeclarationTypeSpec>(x.t));
    Put('('), Walk(std::get<std::list<LetterSpec>>(x.t), ", "), Put(')');
  }
  void Unparse(const LetterSpec &x) {  // R865
    Put(*std::get<const char *>(x.t));
    auto second{std::get<std::optional<const char *>>(x.t)};
    if (second.has_value()) {
      Put('-'), Put(**second);
    }
  }
  void Unparse(const ImportStmt &x) {  // R867
    Word("IMPORT");
    switch (x.kind) {
    case common::ImportKind::Default: Walk(" :: ", x.names, ", "); break;
    case common::ImportKind::Only:
      Put(", "), Word("ONLY: ");
      Walk(x.names, ", ");
      break;
    case common::ImportKind::None: Word(", NONE"); break;
    case common::ImportKind::All: Word(", ALL"); break;
    default: CRASH_NO_CASE;
    }
  }
  void Unparse(const NamelistStmt &x) {  // R868
    Word("NAMELIST"), Walk(x.v, ", ");
  }
  void Unparse(const NamelistStmt::Group &x) {
    Put('/'), Walk(std::get<Name>(x.t)), Put('/');
    Walk(std::get<std::list<Name>>(x.t), ", ");
  }
  void Unparse(const EquivalenceStmt &x) {  // R870, R871
    Word("EQUIVALENCE");
    const char *separator{" "};
    for (const std::list<EquivalenceObject> &y : x.v) {
      Put(separator), Put('('), Walk(y), Put(')');
      separator = ", ";
    }
  }
  void Unparse(const CommonStmt &x) {  // R873
    Word("COMMON ");
    Walk(x.blocks);
  }
  void Unparse(const CommonBlockObject &x) {  // R874
    Walk(std::get<Name>(x.t));
    Walk("(", std::get<std::optional<ArraySpec>>(x.t), ")");
  }
  void Unparse(const CommonStmt::Block &x) {
    Walk("/", std::get<std::optional<Name>>(x.t), "/");
    Walk(std::get<std::list<CommonBlockObject>>(x.t));
  }

  void Unparse(const Substring &x) {  // R908, R909
    Walk(std::get<DataRef>(x.t));
    Put('('), Walk(std::get<SubstringRange>(x.t)), Put(')');
  }
  void Unparse(const CharLiteralConstantSubstring &x) {
    Walk(std::get<CharLiteralConstant>(x.t));
    Put('('), Walk(std::get<SubstringRange>(x.t)), Put(')');
  }
  void Unparse(const SubstringRange &x) {  // R910
    Walk(x.t, ":");
  }
  void Unparse(const PartRef &x) {  // R912
    Walk(x.name);
    Walk("(", x.subscripts, ",", ")");
    Walk(x.imageSelector);
  }
  void Unparse(const StructureComponent &x) {  // R913
    Walk(x.base);
    if (structureComponents_.find(x.component.source) !=
        structureComponents_.end()) {
      Put('.');
    } else {
      Put('%');
    }
    Walk(x.component);
  }
  void Unparse(const ArrayElement &x) {  // R917
    Walk(x.base);
    Put('('), Walk(x.subscripts, ","), Put(')');
  }
  void Unparse(const SubscriptTriplet &x) {  // R921
    Walk(std::get<0>(x.t)), Put(':'), Walk(std::get<1>(x.t));
    Walk(":", std::get<2>(x.t));
  }
  void Unparse(const ImageSelector &x) {  // R924
    Put('['), Walk(std::get<std::list<Cosubscript>>(x.t), ",");
    Walk(",", std::get<std::list<ImageSelectorSpec>>(x.t), ","), Put(']');
  }
  void Before(const ImageSelectorSpec::Stat &) {  // R926
    Word("STAT=");
  }
  void Before(const ImageSelectorSpec::Team &) { Word("TEAM="); }
  void Before(const ImageSelectorSpec::Team_Number &) { Word("TEAM_NUMBER="); }
  void Unparse(const AllocateStmt &x) {  // R927
    Word("ALLOCATE(");
    Walk(std::get<std::optional<TypeSpec>>(x.t), "::");
    Walk(std::get<std::list<Allocation>>(x.t), ", ");
    Walk(", ", std::get<std::list<AllocOpt>>(x.t), ", "), Put(')');
  }
  void Before(const AllocOpt &x) {  // R928, R931
    std::visit(
        common::visitors{
            [&](const AllocOpt::Mold &) { Word("MOLD="); },
            [&](const AllocOpt::Source &) { Word("SOURCE="); },
            [](const StatOrErrmsg &) {},
        },
        x.u);
  }
  void Unparse(const Allocation &x) {  // R932
    Walk(std::get<AllocateObject>(x.t));
    Walk("(", std::get<std::list<AllocateShapeSpec>>(x.t), ",", ")");
    Walk("[", std::get<std::optional<AllocateCoarraySpec>>(x.t), "]");
  }
  void Unparse(const AllocateShapeSpec &x) {  // R934 & R938
    Walk(std::get<std::optional<BoundExpr>>(x.t), ":");
    Walk(std::get<BoundExpr>(x.t));
  }
  void Unparse(const AllocateCoarraySpec &x) {  // R937
    Walk(std::get<std::list<AllocateCoshapeSpec>>(x.t), ",", ",");
    Walk(std::get<std::optional<BoundExpr>>(x.t), ":"), Put('*');
  }
  void Unparse(const NullifyStmt &x) {  // R939
    Word("NULLIFY("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const DeallocateStmt &x) {  // R941
    Word("DEALLOCATE(");
    Walk(std::get<std::list<AllocateObject>>(x.t), ", ");
    Walk(", ", std::get<std::list<StatOrErrmsg>>(x.t), ", "), Put(')');
  }
  void Before(const StatOrErrmsg &x) {  // R942 & R1165
    std::visit(
        common::visitors{
            [&](const StatVariable &) { Word("STAT="); },
            [&](const MsgVariable &) { Word("ERRMSG="); },
        },
        x.u);
  }

  // R1001 - R1022
  void Unparse(const Expr::Parentheses &x) { Put('('), Walk(x.v), Put(')'); }
  void Before(const Expr::UnaryPlus &x) { Put("+"); }
  void Before(const Expr::Negate &x) { Put("-"); }
  void Before(const Expr::NOT &x) { Word(".NOT."); }
  void Unparse(const Expr::PercentLoc &x) {
    Word("%LOC("), Walk(x.v), Put(')');
  }
  void Unparse(const Expr::Power &x) { Walk(x.t, "**"); }
  void Unparse(const Expr::Multiply &x) { Walk(x.t, "*"); }
  void Unparse(const Expr::Divide &x) { Walk(x.t, "/"); }
  void Unparse(const Expr::Add &x) { Walk(x.t, "+"); }
  void Unparse(const Expr::Subtract &x) { Walk(x.t, "-"); }
  void Unparse(const Expr::Concat &x) { Walk(x.t, "//"); }
  void Unparse(const Expr::LT &x) { Walk(x.t, "<"); }
  void Unparse(const Expr::LE &x) { Walk(x.t, "<="); }
  void Unparse(const Expr::EQ &x) { Walk(x.t, "=="); }
  void Unparse(const Expr::NE &x) { Walk(x.t, "/="); }
  void Unparse(const Expr::GE &x) { Walk(x.t, ">="); }
  void Unparse(const Expr::GT &x) { Walk(x.t, ">"); }
  void Unparse(const Expr::AND &x) { Walk(x.t, ".AND."); }
  void Unparse(const Expr::OR &x) { Walk(x.t, ".OR."); }
  void Unparse(const Expr::EQV &x) { Walk(x.t, ".EQV."); }
  void Unparse(const Expr::NEQV &x) { Walk(x.t, ".NEQV."); }
  void Unparse(const Expr::XOR &x) { Walk(x.t, ".XOR."); }
  void Unparse(const Expr::ComplexConstructor &x) {
    Put('('), Walk(x.t, ","), Put(')');
  }
  void Unparse(const Expr::DefinedBinary &x) {
    Walk(std::get<1>(x.t));  // left
    Walk(std::get<DefinedOpName>(x.t));
    Walk(std::get<2>(x.t));  // right
  }
  void Unparse(const DefinedOpName &x) {  // R1003, R1023, R1414, & R1415
    Walk(x.v);
  }
  void Unparse(const AssignmentStmt &x) {  // R1032
    Walk(x.t, " = ");
  }
  void Unparse(const PointerAssignmentStmt &x) {  // R1033, R1034, R1038
    Walk(std::get<DataRef>(x.t));
    std::visit(
        common::visitors{
            [&](const std::list<BoundsRemapping> &y) {
              Put('('), Walk(y), Put(')');
            },
            [&](const std::list<BoundsSpec> &y) { Walk("(", y, ", ", ")"); },
        },
        std::get<PointerAssignmentStmt::Bounds>(x.t).u);
    Put(" => "), Walk(std::get<Expr>(x.t));
  }
  void Post(const BoundsSpec &) {  // R1035
    Put(':');
  }
  void Unparse(const BoundsRemapping &x) {  // R1036
    Walk(x.t, ":");
  }
  void Unparse(const WhereStmt &x) {  // R1041, R1045, R1046
    Word("WHERE ("), Walk(x.t, ") ");
  }
  void Unparse(const WhereConstructStmt &x) {  // R1043
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("WHERE ("), Walk(std::get<LogicalExpr>(x.t)), Put(')');
    Indent();
  }
  void Unparse(const MaskedElsewhereStmt &x) {  // R1047
    Outdent();
    Word("ELSEWHERE ("), Walk(std::get<LogicalExpr>(x.t)), Put(')');
    Walk(" ", std::get<std::optional<Name>>(x.t));
    Indent();
  }
  void Unparse(const ElsewhereStmt &x) {  // R1048
    Outdent(), Word("ELSEWHERE"), Walk(" ", x.v), Indent();
  }
  void Unparse(const EndWhereStmt &x) {  // R1049
    Outdent(), Word("END WHERE"), Walk(" ", x.v);
  }
  void Unparse(const ForallConstructStmt &x) {  // R1051
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("FORALL"), Walk(std::get<common::Indirection<ConcurrentHeader>>(x.t));
    Indent();
  }
  void Unparse(const EndForallStmt &x) {  // R1054
    Outdent(), Word("END FORALL"), Walk(" ", x.v);
  }
  void Before(const ForallStmt &) {  // R1055
    Word("FORALL");
  }

  void Unparse(const AssociateStmt &x) {  // R1103
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("ASSOCIATE (");
    Walk(std::get<std::list<Association>>(x.t), ", "), Put(')'), Indent();
  }
  void Unparse(const Association &x) {  // R1104
    Walk(x.t, " => ");
  }
  void Unparse(const EndAssociateStmt &x) {  // R1106
    Outdent(), Word("END ASSOCIATE"), Walk(" ", x.v);
  }
  void Unparse(const BlockStmt &x) {  // R1108
    Walk(x.v, ": "), Word("BLOCK"), Indent();
  }
  void Unparse(const EndBlockStmt &x) {  // R1110
    Outdent(), Word("END BLOCK"), Walk(" ", x.v);
  }
  void Unparse(const ChangeTeamStmt &x) {  // R1112
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("CHANGE TEAM ("), Walk(std::get<TeamVariable>(x.t));
    Walk(", ", std::get<std::list<CoarrayAssociation>>(x.t), ", ");
    Walk(", ", std::get<std::list<StatOrErrmsg>>(x.t), ", "), Put(')');
    Indent();
  }
  void Unparse(const CoarrayAssociation &x) {  // R1113
    Walk(x.t, " => ");
  }
  void Unparse(const EndChangeTeamStmt &x) {  // R1114
    Outdent(), Word("END TEAM (");
    Walk(std::get<std::list<StatOrErrmsg>>(x.t), ", ");
    Put(')'), Walk(" ", std::get<std::optional<Name>>(x.t));
  }
  void Unparse(const CriticalStmt &x) {  // R1117
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("CRITICAL ("), Walk(std::get<std::list<StatOrErrmsg>>(x.t), ", ");
    Put(')'), Indent();
  }
  void Unparse(const EndCriticalStmt &x) {  // R1118
    Outdent(), Word("END CRITICAL"), Walk(" ", x.v);
  }
  void Unparse(const DoConstruct &x) {  // R1119, R1120
    Walk(std::get<Statement<NonLabelDoStmt>>(x.t));
    Indent(), Walk(std::get<Block>(x.t), ""), Outdent();
    Walk(std::get<Statement<EndDoStmt>>(x.t));
  }
  void Unparse(const LabelDoStmt &x) {  // R1121
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("DO "), Walk(std::get<Label>(x.t));
    Walk(" ", std::get<std::optional<LoopControl>>(x.t));
  }
  void Unparse(const NonLabelDoStmt &x) {  // R1122
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("DO "), Walk(std::get<std::optional<LoopControl>>(x.t));
  }
  void Unparse(const LoopControl &x) {  // R1123
    std::visit(
        common::visitors{
            [&](const ScalarLogicalExpr &y) {
              Word("WHILE ("), Walk(y), Put(')');
            },
            [&](const auto &y) { Walk(y); },
        },
        x.u);
  }
  void Unparse(const ConcurrentHeader &x) {  // R1125
    Put('('), Walk(std::get<std::optional<IntegerTypeSpec>>(x.t), "::");
    Walk(std::get<std::list<ConcurrentControl>>(x.t), ", ");
    Walk(", ", std::get<std::optional<ScalarLogicalExpr>>(x.t)), Put(')');
  }
  void Unparse(const ConcurrentControl &x) {  // R1126 - R1128
    Walk(std::get<Name>(x.t)), Put('='), Walk(std::get<1>(x.t));
    Put(':'), Walk(std::get<2>(x.t));
    Walk(":", std::get<std::optional<ScalarIntExpr>>(x.t));
  }
  void Before(const LoopControl::Concurrent &x) {  // R1129
    Word("CONCURRENT");
  }
  void Unparse(const LocalitySpec::Local &x) {
    Word("LOCAL("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const LocalitySpec::LocalInit &x) {
    Word("LOCAL_INIT("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const LocalitySpec::Shared &x) {
    Word("SHARED("), Walk(x.v, ", "), Put(')');
  }
  void Post(const LocalitySpec::DefaultNone &x) { Word("DEFAULT(NONE)"); }
  void Unparse(const EndDoStmt &x) {  // R1132
    Word("END DO"), Walk(" ", x.v);
  }
  void Unparse(const CycleStmt &x) {  // R1133
    Word("CYCLE"), Walk(" ", x.v);
  }
  void Unparse(const IfThenStmt &x) {  // R1135
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("IF ("), Walk(std::get<ScalarLogicalExpr>(x.t));
    Put(") "), Word("THEN"), Indent();
  }
  void Unparse(const ElseIfStmt &x) {  // R1136
    Outdent(), Word("ELSE IF (");
    Walk(std::get<ScalarLogicalExpr>(x.t)), Put(") "), Word("THEN");
    Walk(" ", std::get<std::optional<Name>>(x.t)), Indent();
  }
  void Unparse(const ElseStmt &x) {  // R1137
    Outdent(), Word("ELSE"), Walk(" ", x.v), Indent();
  }
  void Unparse(const EndIfStmt &x) {  // R1138
    Outdent(), Word("END IF"), Walk(" ", x.v);
  }
  void Unparse(const IfStmt &x) {  // R1139
    Word("IF ("), Walk(x.t, ") ");
  }
  void Unparse(const SelectCaseStmt &x) {  // R1141, R1144
    Walk(std::get<std::optional<Name>>(x.t), ": ");
    Word("SELECT CASE (");
    Walk(std::get<Scalar<Expr>>(x.t)), Put(')'), Indent();
  }
  void Unparse(const CaseStmt &x) {  // R1142
    Outdent(), Word("CASE "), Walk(std::get<CaseSelector>(x.t));
    Walk(" ", std::get<std::optional<Name>>(x.t)), Indent();
  }
  void Unparse(const EndSelectStmt &x) {  // R1143 & R1151 & R1155
    Outdent(), Word("END SELECT"), Walk(" ", x.v);
  }
  void Unparse(const CaseSelector &x) {  // R1145
    std::visit(
        common::visitors{
            [&](const std::list<CaseValueRange> &y) {
              Put('('), Walk(y), Put(')');
            },
            [&](const Default &) { Word("DEFAULT"); },
        },
        x.u);
  }
  void Unparse(const CaseValueRange::Range &x) {  // R1146
    Walk(x.lower), Put(':'), Walk(x.upper);
  }
  void Unparse(const SelectRankStmt &x) {  // R1149
    Walk(std::get<0>(x.t), ": ");
    Word("SELECT RANK ("), Walk(std::get<1>(x.t), " => ");
    Walk(std::get<Selector>(x.t)), Put(')'), Indent();
  }
  void Unparse(const SelectRankCaseStmt &x) {  // R1150
    Outdent(), Word("RANK ");
    std::visit(
        common::visitors{
            [&](const ScalarIntConstantExpr &y) {
              Put('('), Walk(y), Put(')');
            },
            [&](const Star &) { Put("(*)"); },
            [&](const Default &) { Word("DEFAULT"); },
        },
        std::get<SelectRankCaseStmt::Rank>(x.t).u);
    Walk(" ", std::get<std::optional<Name>>(x.t)), Indent();
  }
  void Unparse(const SelectTypeStmt &x) {  // R1153
    Walk(std::get<0>(x.t), ": ");
    Word("SELECT TYPE ("), Walk(std::get<1>(x.t), " => ");
    Walk(std::get<Selector>(x.t)), Put(')'), Indent();
  }
  void Unparse(const TypeGuardStmt &x) {  // R1154
    Outdent(), Walk(std::get<TypeGuardStmt::Guard>(x.t));
    Walk(" ", std::get<std::optional<Name>>(x.t)), Indent();
  }
  void Unparse(const TypeGuardStmt::Guard &x) {
    std::visit(
        common::visitors{
            [&](const TypeSpec &y) { Word("TYPE IS ("), Walk(y), Put(')'); },
            [&](const DerivedTypeSpec &y) {
              Word("CLASS IS ("), Walk(y), Put(')');
            },
            [&](const Default &) { Word("CLASS DEFAULT"); },
        },
        x.u);
  }
  void Unparse(const ExitStmt &x) {  // R1156
    Word("EXIT"), Walk(" ", x.v);
  }
  void Before(const GotoStmt &x) {  // R1157
    Word("GO TO ");
  }
  void Unparse(const ComputedGotoStmt &x) {  // R1158
    Word("GO TO ("), Walk(x.t, "), ");
  }
  void Unparse(const ContinueStmt &x) {  // R1159
    Word("CONTINUE");
  }
  void Unparse(const StopStmt &x) {  // R1160, R1161
    if (std::get<StopStmt::Kind>(x.t) == StopStmt::Kind::ErrorStop) {
      Word("ERROR ");
    }
    Word("STOP"), Walk(" ", std::get<std::optional<StopCode>>(x.t));
    Walk(", QUIET=", std::get<std::optional<ScalarLogicalExpr>>(x.t));
  }
  void Unparse(const FailImageStmt &x) {  // R1163
    Word("FAIL IMAGE");
  }
  void Unparse(const SyncAllStmt &x) {  // R1164
    Word("SYNC ALL ("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const SyncImagesStmt &x) {  // R1166
    Word("SYNC IMAGES (");
    Walk(std::get<SyncImagesStmt::ImageSet>(x.t));
    Walk(", ", std::get<std::list<StatOrErrmsg>>(x.t), ", "), Put(')');
  }
  void Unparse(const SyncMemoryStmt &x) {  // R1168
    Word("SYNC MEMORY ("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const SyncTeamStmt &x) {  // R1169
    Word("SYNC TEAM ("), Walk(std::get<TeamVariable>(x.t));
    Walk(", ", std::get<std::list<StatOrErrmsg>>(x.t), ", "), Put(')');
  }
  void Unparse(const EventPostStmt &x) {  // R1170
    Word("EVENT POST ("), Walk(std::get<EventVariable>(x.t));
    Walk(", ", std::get<std::list<StatOrErrmsg>>(x.t), ", "), Put(')');
  }
  void Before(const EventWaitStmt::EventWaitSpec &x) {  // R1173, R1174
    std::visit(
        common::visitors{
            [&](const ScalarIntExpr &x) { Word("UNTIL_COUNT="); },
            [](const StatOrErrmsg &) {},
        },
        x.u);
  }
  void Unparse(const EventWaitStmt &x) {  // R1170
    Word("EVENT WAIT ("), Walk(std::get<EventVariable>(x.t));
    Walk(", ", std::get<std::list<EventWaitStmt::EventWaitSpec>>(x.t), ", ");
    Put(')');
  }
  void Unparse(const FormTeamStmt &x) {  // R1175
    Word("FORM TEAM ("), Walk(std::get<ScalarIntExpr>(x.t));
    Put(','), Walk(std::get<TeamVariable>(x.t));
    Walk(", ", std::get<std::list<FormTeamStmt::FormTeamSpec>>(x.t), ", ");
    Put(')');
  }
  void Before(const FormTeamStmt::FormTeamSpec &x) {  // R1176, R1177
    std::visit(
        common::visitors{
            [&](const ScalarIntExpr &x) { Word("NEW_INDEX="); },
            [](const StatOrErrmsg &) {},
        },
        x.u);
  }
  void Unparse(const LockStmt &x) {  // R1178
    Word("LOCK ("), Walk(std::get<LockVariable>(x.t));
    Walk(", ", std::get<std::list<LockStmt::LockStat>>(x.t), ", ");
    Put(')');
  }
  void Before(const LockStmt::LockStat &x) {  // R1179
    std::visit(
        common::visitors{
            [&](const ScalarLogicalVariable &) { Word("ACQUIRED_LOCK="); },
            [](const StatOrErrmsg &y) {},
        },
        x.u);
  }
  void Unparse(const UnlockStmt &x) {  // R1180
    Word("UNLOCK ("), Walk(std::get<LockVariable>(x.t));
    Walk(", ", std::get<std::list<StatOrErrmsg>>(x.t), ", ");
    Put(')');
  }

  void Unparse(const OpenStmt &x) {  // R1204
    Word("OPEN ("), Walk(x.v, ", "), Put(')');
  }
  bool Pre(const ConnectSpec &x) {  // R1205
    return std::visit(
        common::visitors{
            [&](const FileUnitNumber &) {
              Word("UNIT=");
              return true;
            },
            [&](const FileNameExpr &) {
              Word("FILE=");
              return true;
            },
            [&](const ConnectSpec::CharExpr &y) {
              Walk(y.t, "=");
              return false;
            },
            [&](const MsgVariable &) {
              Word("IOMSG=");
              return true;
            },
            [&](const StatVariable &) {
              Word("IOSTAT=");
              return true;
            },
            [&](const ConnectSpec::Recl &) {
              Word("RECL=");
              return true;
            },
            [&](const ConnectSpec::Newunit &) {
              Word("NEWUNIT=");
              return true;
            },
            [&](const ErrLabel &) {
              Word("ERR=");
              return true;
            },
            [&](const StatusExpr &) {
              Word("STATUS=");
              return true;
            },
        },
        x.u);
  }
  void Unparse(const CloseStmt &x) {  // R1208
    Word("CLOSE ("), Walk(x.v, ", "), Put(')');
  }
  void Before(const CloseStmt::CloseSpec &x) {  // R1209
    std::visit(
        common::visitors{
            [&](const FileUnitNumber &) { Word("UNIT="); },
            [&](const StatVariable &) { Word("IOSTAT="); },
            [&](const MsgVariable &) { Word("IOMSG="); },
            [&](const ErrLabel &) { Word("ERR="); },
            [&](const StatusExpr &) { Word("STATUS="); },
        },
        x.u);
  }
  void Unparse(const ReadStmt &x) {  // R1210
    Word("READ ");
    if (x.iounit) {
      Put('('), Walk(x.iounit);
      if (x.format) {
        Put(", "), Walk(x.format);
      }
      Walk(", ", x.controls, ", ");
      Put(')');
    } else if (x.format) {
      Walk(x.format);
      if (!x.items.empty()) {
        Put(", ");
      }
    } else {
      Put('('), Walk(x.controls, ", "), Put(')');
    }
    Walk(" ", x.items, ", ");
  }
  void Unparse(const WriteStmt &x) {  // R1211
    Word("WRITE (");
    if (x.iounit) {
      Walk(x.iounit);
      if (x.format) {
        Put(", "), Walk(x.format);
      }
      Walk(", ", x.controls, ", ");
    } else {
      Walk(x.controls, ", ");
    }
    Put(')'), Walk(" ", x.items, ", ");
  }
  void Unparse(const PrintStmt &x) {  // R1212
    Word("PRINT "), Walk(std::get<Format>(x.t));
    Walk(", ", std::get<std::list<OutputItem>>(x.t), ", ");
  }
  bool Pre(const IoControlSpec &x) {  // R1213
    return std::visit(
        common::visitors{
            [&](const IoUnit &) {
              Word("UNIT=");
              return true;
            },
            [&](const Format &) {
              Word("FMT=");
              return true;
            },
            [&](const Name &) {
              Word("NML=");
              return true;
            },
            [&](const IoControlSpec::CharExpr &y) {
              Walk(y.t, "=");
              return false;
            },
            [&](const IoControlSpec::Asynchronous &) {
              Word("ASYNCHRONOUS=");
              return true;
            },
            [&](const EndLabel &) {
              Word("END=");
              return true;
            },
            [&](const EorLabel &) {
              Word("EOR=");
              return true;
            },
            [&](const ErrLabel &) {
              Word("ERR=");
              return true;
            },
            [&](const IdVariable &) {
              Word("ID=");
              return true;
            },
            [&](const MsgVariable &) {
              Word("IOMSG=");
              return true;
            },
            [&](const StatVariable &) {
              Word("IOSTAT=");
              return true;
            },
            [&](const IoControlSpec::Pos &) {
              Word("POS=");
              return true;
            },
            [&](const IoControlSpec::Rec &) {
              Word("REC=");
              return true;
            },
            [&](const IoControlSpec::Size &) {
              Word("SIZE=");
              return true;
            },
        },
        x.u);
  }
  void Unparse(const InputImpliedDo &x) {  // R1218
    Put('('), Walk(std::get<std::list<InputItem>>(x.t), ", "), Put(", ");
    Walk(std::get<IoImpliedDoControl>(x.t)), Put(')');
  }
  void Unparse(const OutputImpliedDo &x) {  // R1219
    Put('('), Walk(std::get<std::list<OutputItem>>(x.t), ", "), Put(", ");
    Walk(std::get<IoImpliedDoControl>(x.t)), Put(')');
  }
  void Unparse(const WaitStmt &x) {  // R1222
    Word("WAIT ("), Walk(x.v, ", "), Put(')');
  }
  void Before(const WaitSpec &x) {  // R1223
    std::visit(
        common::visitors{
            [&](const FileUnitNumber &) { Word("UNIT="); },
            [&](const EndLabel &) { Word("END="); },
            [&](const EorLabel &) { Word("EOR="); },
            [&](const ErrLabel &) { Word("ERR="); },
            [&](const IdExpr &) { Word("ID="); },
            [&](const MsgVariable &) { Word("IOMSG="); },
            [&](const StatVariable &) { Word("IOSTAT="); },
        },
        x.u);
  }
  void Unparse(const BackspaceStmt &x) {  // R1224
    Word("BACKSPACE ("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const EndfileStmt &x) {  // R1225
    Word("ENDFILE ("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const RewindStmt &x) {  // R1226
    Word("REWIND ("), Walk(x.v, ", "), Put(')');
  }
  void Before(const PositionOrFlushSpec &x) {  // R1227 & R1229
    std::visit(
        common::visitors{
            [&](const FileUnitNumber &) { Word("UNIT="); },
            [&](const MsgVariable &) { Word("IOMSG="); },
            [&](const StatVariable &) { Word("IOSTAT="); },
            [&](const ErrLabel &) { Word("ERR="); },
        },
        x.u);
  }
  void Unparse(const FlushStmt &x) {  // R1228
    Word("FLUSH ("), Walk(x.v, ", "), Put(')');
  }
  void Unparse(const InquireStmt &x) {  // R1230
    Word("INQUIRE (");
    std::visit(
        common::visitors{
            [&](const InquireStmt::Iolength &y) {
              Word("IOLENGTH="), Walk(y.t, ") ");
            },
            [&](const std::list<InquireSpec> &y) { Walk(y, ", "), Put(')'); },
        },
        x.u);
  }
  bool Pre(const InquireSpec &x) {  // R1231
    return std::visit(
        common::visitors{
            [&](const FileUnitNumber &) {
              Word("UNIT=");
              return true;
            },
            [&](const FileNameExpr &) {
              Word("FILE=");
              return true;
            },
            [&](const InquireSpec::CharVar &y) {
              Walk(y.t, "=");
              return false;
            },
            [&](const InquireSpec::IntVar &y) {
              Walk(y.t, "=");
              return false;
            },
            [&](const InquireSpec::LogVar &y) {
              Walk(y.t, "=");
              return false;
            },
            [&](const IdExpr &) {
              Word("ID=");
              return true;
            },
            [&](const ErrLabel &) {
              Word("ERR=");
              return true;
            },
        },
        x.u);
  }

  void Before(const FormatStmt &) {  // R1301
    Word("FORMAT");
  }
  void Unparse(const format::FormatSpecification &x) {  // R1302, R1303, R1305
    Put('('), Walk("", x.items, ",", x.unlimitedItems.empty() ? "" : ",");
    Walk("*(", x.unlimitedItems, ",", ")"), Put(')');
  }
  void Unparse(const format::FormatItem &x) {  // R1304, R1306, R1321
    if (x.repeatCount.has_value()) {
      Walk(*x.repeatCount);
    }
    std::visit(
        common::visitors{
            [&](const std::string &y) {
              Put(QuoteCharacterLiteral(y, true, backslashEscapes_));
            },
            [&](const std::list<format::FormatItem> &y) {
              Walk("(", y, ",", ")");
            },
            [&](const auto &y) { Walk(y); },
        },
        x.u);
  }
  void Unparse(
      const format::IntrinsicTypeDataEditDesc &x) {  // R1307(1/2) - R1311
    switch (x.kind) {
#define FMT(x) \
  case format::IntrinsicTypeDataEditDesc::Kind::x: Put(#x); break
      FMT(I);
      FMT(B);
      FMT(O);
      FMT(Z);
      FMT(F);
      FMT(E);
      FMT(EN);
      FMT(ES);
      FMT(EX);
      FMT(G);
      FMT(L);
      FMT(A);
      FMT(D);
#undef FMT
    default: CRASH_NO_CASE;
    }
    Walk(x.width), Walk(".", x.digits), Walk("E", x.exponentWidth);
  }
  void Unparse(const format::DerivedTypeDataEditDesc &x) {  // R1307(2/2), R1312
    Word("DT");
    if (!x.type.empty()) {
      Put('"'), Put(x.type), Put('"');
    }
    Walk("(", x.parameters, ",", ")");
  }
  void Unparse(const format::ControlEditDesc &x) {  // R1313, R1315-R1320
    switch (x.kind) {
    case format::ControlEditDesc::Kind::T:
      Word("T");
      Walk(x.count);
      break;
    case format::ControlEditDesc::Kind::TL:
      Word("TL");
      Walk(x.count);
      break;
    case format::ControlEditDesc::Kind::TR:
      Word("TR");
      Walk(x.count);
      break;
    case format::ControlEditDesc::Kind::X:
      if (x.count != 1) {
        Walk(x.count);
      }
      Word("X");
      break;
    case format::ControlEditDesc::Kind::Slash:
      if (x.count != 1) {
        Walk(x.count);
      }
      Put('/');
      break;
    case format::ControlEditDesc::Kind::Colon: Put(':'); break;
    case format::ControlEditDesc::Kind::P:
      Walk(x.count);
      Word("P");
      break;
#define FMT(x) \
  case format::ControlEditDesc::Kind::x: Put(#x); break
      FMT(SS);
      FMT(SP);
      FMT(S);
      FMT(BN);
      FMT(BZ);
      FMT(RU);
      FMT(RD);
      FMT(RZ);
      FMT(RN);
      FMT(RC);
      FMT(RP);
      FMT(DC);
      FMT(DP);
#undef FMT
    default: CRASH_NO_CASE;
    }
  }

  void Before(const MainProgram &x) {  // R1401
    if (!std::get<std::optional<Statement<ProgramStmt>>>(x.t)) {
      Indent();
    }
  }
  void Before(const ProgramStmt &x) {  // R1402
    Word("PROGRAM "), Indent();
  }
  void Unparse(const EndProgramStmt &x) {  // R1403
    EndSubprogram("PROGRAM", x.v);
  }
  void Before(const ModuleStmt &) {  // R1405
    Word("MODULE "), Indent();
  }
  void Unparse(const EndModuleStmt &x) {  // R1406
    EndSubprogram("MODULE", x.v);
  }
  void Unparse(const UseStmt &x) {  // R1409
    Word("USE"), Walk(", ", x.nature), Put(" :: "), Walk(x.moduleName);
    std::visit(
        common::visitors{
            [&](const std::list<Rename> &y) { Walk(", ", y, ", "); },
            [&](const std::list<Only> &y) { Walk(", ONLY: ", y, ", "); },
        },
        x.u);
  }
  void Unparse(const Rename &x) {  // R1411
    std::visit(
        common::visitors{
            [&](const Rename::Names &y) { Walk(y.t, " => "); },
            [&](const Rename::Operators &y) {
              Word("OPERATOR("), Walk(y.t, ") => OPERATOR("), Put(")");
            },
        },
        x.u);
  }
  void Unparse(const SubmoduleStmt &x) {  // R1417
    Word("SUBMODULE ("), WalkTupleElements(x.t, ")"), Indent();
  }
  void Unparse(const ParentIdentifier &x) {  // R1418
    Walk(std::get<Name>(x.t)), Walk(":", std::get<std::optional<Name>>(x.t));
  }
  void Unparse(const EndSubmoduleStmt &x) {  // R1419
    EndSubprogram("SUBMODULE", x.v);
  }
  void Unparse(const BlockDataStmt &x) {  // R1421
    Word("BLOCK DATA"), Walk(" ", x.v), Indent();
  }
  void Unparse(const EndBlockDataStmt &x) {  // R1422
    EndSubprogram("BLOCK DATA", x.v);
  }

  void Unparse(const InterfaceStmt &x) {  // R1503
    std::visit(
        common::visitors{
            [&](const std::optional<GenericSpec> &y) {
              Word("INTERFACE"), Walk(" ", y);
            },
            [&](const Abstract &) { Word("ABSTRACT INTERFACE"); },
        },
        x.u);
    Indent();
  }
  void Unparse(const EndInterfaceStmt &x) {  // R1504
    Outdent(), Word("END INTERFACE"), Walk(" ", x.v);
  }
  void Unparse(const ProcedureStmt &x) {  // R1506
    if (std::get<ProcedureStmt::Kind>(x.t) ==
        ProcedureStmt::Kind::ModuleProcedure) {
      Word("MODULE ");
    }
    Word("PROCEDURE :: ");
    Walk(std::get<std::list<Name>>(x.t), ", ");
  }
  void Before(const GenericSpec &x) {  // R1508, R1509
    std::visit(
        common::visitors{
            [&](const DefinedOperator &x) { Word("OPERATOR("); },
            [&](const GenericSpec::Assignment &) { Word("ASSIGNMENT(=)"); },
            [&](const GenericSpec::ReadFormatted &) {
              Word("READ(FORMATTED)");
            },
            [&](const GenericSpec::ReadUnformatted &) {
              Word("READ(UNFORMATTED)");
            },
            [&](const GenericSpec::WriteFormatted &) {
              Word("WRITE(FORMATTED)");
            },
            [&](const GenericSpec::WriteUnformatted &) {
              Word("WRITE(UNFORMATTED)");
            },
            [](const auto &) {},
        },
        x.u);
  }
  void Post(const GenericSpec &x) {
    std::visit(
        common::visitors{
            [&](const DefinedOperator &x) { Put(')'); },
            [](const auto &) {},
        },
        x.u);
  }
  void Unparse(const GenericStmt &x) {  // R1510
    Word("GENERIC"), Walk(", ", std::get<std::optional<AccessSpec>>(x.t));
    Put(" :: "), Walk(std::get<GenericSpec>(x.t)), Put(" => ");
    Walk(std::get<std::list<Name>>(x.t), ", ");
  }
  void Unparse(const ExternalStmt &x) {  // R1511
    Word("EXTERNAL :: "), Walk(x.v, ", ");
  }
  void Unparse(const ProcedureDeclarationStmt &x) {  // R1512
    Word("PROCEDURE ("), Walk(std::get<std::optional<ProcInterface>>(x.t));
    Put(')'), Walk(", ", std::get<std::list<ProcAttrSpec>>(x.t), ", ");
    Put(" :: "), Walk(std::get<std::list<ProcDecl>>(x.t), ", ");
  }
  void Unparse(const ProcInterface &x) {  // R1513
    std::visit(
        common::visitors{
            [&](const DeclarationTypeSpec &d) {
              std::visit(
                  common::visitors{
                      [&](const IntrinsicTypeSpec &t) {
                        // Emit TYPE(REAL) to ensure no conflict with a symbol
                        // REAL
                        Word("TYPE("), Walk(t), Word(")");
                      },
                      [&](const auto &t) { Walk(t); },
                  },
                  d.u);
            },
            [&](const Name &n) { Walk(n); },
        },
        x.u);
  }
  void Unparse(const ProcDecl &x) {  // R1515
    Walk(std::get<Name>(x.t));
    Walk(" => ", std::get<std::optional<ProcPointerInit>>(x.t));
  }
  void Unparse(const IntrinsicStmt &x) {  // R1519
    Word("INTRINSIC :: "), Walk(x.v, ", ");
  }
  void Unparse(const FunctionReference &x) {  // R1520
    Walk(std::get<ProcedureDesignator>(x.v.t));
    Put('('), Walk(std::get<std::list<ActualArgSpec>>(x.v.t), ", "), Put(')');
  }
  void Unparse(const CallStmt &x) {  // R1521
    const auto &pd{std::get<ProcedureDesignator>(x.v.t)};
    const auto &args{std::get<std::list<ActualArgSpec>>(x.v.t)};
    Word("CALL "), Walk(pd);
    if (args.empty()) {
      if (std::holds_alternative<ProcComponentRef>(pd.u)) {
        Put("()");  // pgf90 crashes on CALL to tbp without parentheses
      }
    } else {
      Walk("(", args, ", ", ")");
    }
  }
  void Unparse(const ActualArgSpec &x) {  // R1523
    Walk(std::get<std::optional<Keyword>>(x.t), "=");
    Walk(std::get<ActualArg>(x.t));
  }
  void Unparse(const ActualArg::PercentRef &x) {  // R1524
    Word("%REF("), Walk(x.v), Put(')');
  }
  void Unparse(const ActualArg::PercentVal &x) {
    Word("%VAL("), Walk(x.v), Put(')');
  }
  void Before(const AltReturnSpec &) {  // R1525
    Put('*');
  }
  void Post(const PrefixSpec::Elemental) { Word("ELEMENTAL"); }  // R1527
  void Post(const PrefixSpec::Impure) { Word("IMPURE"); }
  void Post(const PrefixSpec::Module) { Word("MODULE"); }
  void Post(const PrefixSpec::Non_Recursive) { Word("NON_RECURSIVE"); }
  void Post(const PrefixSpec::Pure) { Word("PURE"); }
  void Post(const PrefixSpec::Recursive) { Word("RECURSIVE"); }
  void Unparse(const FunctionStmt &x) {  // R1530
    Walk("", std::get<std::list<PrefixSpec>>(x.t), " ", " ");
    Word("FUNCTION "), Walk(std::get<Name>(x.t)), Put("(");
    Walk(std::get<std::list<Name>>(x.t), ", "), Put(')');
    Walk(" ", std::get<std::optional<Suffix>>(x.t)), Indent();
  }
  void Unparse(const Suffix &x) {  // R1532
    if (x.resultName) {
      Word("RESULT("), Walk(x.resultName), Put(')');
      Walk(" ", x.binding);
    } else {
      Walk(x.binding);
    }
  }
  void Unparse(const EndFunctionStmt &x) {  // R1533
    EndSubprogram("FUNCTION", x.v);
  }
  void Unparse(const SubroutineStmt &x) {  // R1535
    Walk("", std::get<std::list<PrefixSpec>>(x.t), " ", " ");
    Word("SUBROUTINE "), Walk(std::get<Name>(x.t));
    const auto &args{std::get<std::list<DummyArg>>(x.t)};
    const auto &bind{std::get<std::optional<LanguageBindingSpec>>(x.t)};
    if (args.empty()) {
      Walk(" () ", bind);
    } else {
      Walk(" (", args, ", ", ")");
      Walk(" ", bind);
    }
    Indent();
  }
  void Unparse(const EndSubroutineStmt &x) {  // R1537
    EndSubprogram("SUBROUTINE", x.v);
  }
  void Before(const MpSubprogramStmt &) {  // R1539
    Word("MODULE PROCEDURE "), Indent();
  }
  void Unparse(const EndMpSubprogramStmt &x) {  // R1540
    EndSubprogram("PROCEDURE", x.v);
  }
  void Unparse(const EntryStmt &x) {  // R1541
    Word("ENTRY "), Walk(std::get<Name>(x.t)), Put("(");
    Walk(std::get<std::list<DummyArg>>(x.t), ", "), Put(")");
    Walk(" ", std::get<std::optional<Suffix>>(x.t));
  }
  void Unparse(const ReturnStmt &x) {  // R1542
    Word("RETURN"), Walk(" ", x.v);
  }
  void Unparse(const ContainsStmt &x) {  // R1543
    Outdent();
    Word("CONTAINS");
    Indent();
  }
  void Unparse(const StmtFunctionStmt &x) {  // R1544
    Walk(std::get<Name>(x.t)), Put('(');
    Walk(std::get<std::list<Name>>(x.t), ", "), Put(") = ");
    Walk(std::get<Scalar<Expr>>(x.t));
  }

  // Directives, extensions, and deprecated constructs
  void Unparse(const CompilerDirective &x) {
    std::visit(
        common::visitors{
            [&](const std::list<CompilerDirective::IgnoreTKR> &tkr) {
              Word("!DIR$ IGNORE_TKR");  // emitted even if tkr list is empty
              Walk(" ", tkr, ", ");
            },
            [&](const std::list<Name> &names) { Walk("!DIR$ ", names, " "); },
        },
        x.u);
    Put('\n');
  }
  void Unparse(const CompilerDirective::IgnoreTKR &x) {
    const auto &list{std::get<std::list<const char *>>(x.t)};
    if (!list.empty()) {
      Put("(");
      for (const char *tkr : list) {
        Put(*tkr);
      }
      Put(") ");
    }
    Walk(std::get<Name>(x.t));
  }
  // OpenMP Clauses & Directives
  void Unparse(const OmpObject &x) {
    bool isCommon{std::get<OmpObject::Kind>(x.t) == OmpObject::Kind::Common};
    const char *slash{isCommon ? "/" : ""};
    Put(slash), Walk(std::get<Designator>(x.t)), Put(slash);
  }
  void Unparse(const OmpMapType::Always &x) { Word("ALWAYS,"); }
  void Unparse(const OmpMapClause &x) {
    Word("MAP(");
    Walk(std::get<std::optional<OmpMapType>>(x.t), ":");
    Walk(std::get<OmpObjectList>(x.t));
    Put(") ");
  }
  void Unparse(const OmpScheduleModifier &x) {
    Walk(std::get<OmpScheduleModifier::Modifier1>(x.t));
    Walk(",", std::get<std::optional<OmpScheduleModifier::Modifier2>>(x.t));
  }
  void Unparse(const OmpScheduleClause &x) {
    Word("SCHEDULE(");
    Walk(std::get<std::optional<OmpScheduleModifier>>(x.t));
    Walk(std::get<OmpScheduleClause::ScheduleType>(x.t));
    Walk(",", std::get<std::optional<ScalarIntExpr>>(x.t));
    Put(")");
  }
  void Unparse(const OmpAlignedClause &x) {
    Word("ALIGNED("), Walk(std::get<std::list<Name>>(x.t), ",");
    Walk(std::get<std::optional<ScalarIntConstantExpr>>(x.t));
    Put(") ");
  }
  void Unparse(const OmpIfClause &x) {
    Word("IF("),
        Walk(std::get<std::optional<OmpIfClause::DirectiveNameModifier>>(x.t),
            ":");
    Walk(std::get<ScalarLogicalExpr>(x.t));
    Put(") ");
  }
  void Unparse(const OmpLinearClause::WithoutModifier &x) {
    Word("LINEAR("), Walk(x.names, ", ");
    Walk(":", x.step);
    Put(")");
  }
  void Unparse(const OmpLinearClause::WithModifier &x) {
    Word("LINEAR("), Walk(x.modifier), Put("("), Walk(x.names, ","), Put(")");
    Walk(":", x.step);
    Put(")");
  }
  void Unparse(const OmpReductionClause &x) {
    Word("REDUCTION(");
    Walk(std::get<OmpReductionOperator>(x.t));
    Put(":");
    Walk(std::get<std::list<Designator>>(x.t), ",");
    Put(")");
  }
  void Unparse(const OmpDependSinkVecLength &x) {
    Walk(std::get<common::Indirection<DefinedOperator>>(x.t));
    Walk(std::get<ScalarIntConstantExpr>(x.t));
  }
  void Unparse(const OmpDependSinkVec &x) {
    Walk(std::get<Name>(x.t));
    Walk(std::get<std::optional<OmpDependSinkVecLength>>(x.t));
  }
  void Unparse(const OmpDependClause::InOut &x) {
    Put("(");
    Walk(std::get<OmpDependenceType>(x.t));
    Put(":");
    Walk(std::get<std::list<Designator>>(x.t), ",");
    Put(")");
  }
  bool Pre(const OmpDependClause &x) {
    return std::visit(
        common::visitors{
            [&](const OmpDependClause::Source &y) {
              Word("DEPEND(SOURCE)");
              return false;
            },
            [&](const OmpDependClause::Sink &y) {
              Word("DEPEND(SINK:");
              Walk(y.v);
              Put(")");
              return false;
            },
            [&](const OmpDependClause::InOut &y) {
              Word("DEPEND");
              return true;
            },
        },
        x.u);
  }
  bool Pre(const OmpDefaultClause &x) {
    Word("DEFAULT(");
    return true;
  }
  void Post(const OmpDefaultClause &x) { Put(")"); }
  bool Pre(const OmpProcBindClause &x) {
    Word("PROC_BIND(");
    return true;
  }
  void Post(const OmpProcBindClause &x) { Put(")"); }
  void Before(const OmpClause::Defaultmap &x) {
    Word("DEFAULTMAP(TOFROM:SCALAR)");
  }
  void Before(const OmpClause::Inbranch &x) { Word("INBRANCH"); }
  void Before(const OmpClause::Mergeable &x) { Word("MERGEABLE"); }
  void Before(const OmpClause::Nogroup &x) { Word("NOGROUP"); }
  void Before(const OmpClause::Notinbranch &x) { Word("NOTINBRANCH"); }
  void Before(const OmpClause::Untied &x) { Word("UNTIED"); }
  void Unparse(const OmpNowait &) { Word("NOWAIT"); }
  void Unparse(const OmpClause::Collapse &x) {
    Word("COLLAPSE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Copyin &x) {
    Word("COPYIN(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Copyprivate &x) {
    Word("COPYPRIVATE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Device &x) {
    Word("DEVICE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::DistSchedule &x) {
    Word("DIST_SCHEDULE(STATIC,");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Final &x) {
    Word("FINAL(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Firstprivate &x) {
    Word("FIRSTPRIVATE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::From &x) {
    Word("FROM(");
    Walk(x.v, ",");
    Put(")");
  }
  void Unparse(const OmpClause::Grainsize &x) {
    Word("GRAINSIZE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Lastprivate &x) {
    Word("LASTPRIVATE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::NumTasks &x) {
    Word("NUM_TASKS(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::NumTeams &x) {
    Word("NUM_TEAMS(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::NumThreads &x) {
    Word("NUM_THREADS(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Ordered &x) {
    Word("ORDERED");
    Walk("(", x.v, ")");
  }
  void Unparse(const OmpClause::Priority &x) {
    Word("PRIORITY(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Private &x) {
    Word("PRIVATE(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Safelen &x) {
    Word("SAFELEN(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Simdlen &x) {
    Word("SIMDLEN(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::ThreadLimit &x) {
    Word("THREADLIMIT(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::Shared &x) {
    Word("SHARED(");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpClause::To &x) {
    Word("TO(");
    Walk(x.v, ",");
    Put(")");
  }
  void Unparse(const OmpClause::Uniform &x) {
    Word("UNIFORM(");
    Walk(x.v, ",");
    Put(")");
  }
  void Unparse(const OmpClause::UseDevicePtr &x) {
    Word("USE_DEVICE_PTR(");
    Walk(x.v, ",");
    Put(")");
  }
  void Unparse(const OmpLoopDirective &x) {
    std::visit(
        common::visitors{
            [&](const OmpLoopDirective::DistributeParallelDoSimd &) {
              Word("DISTRIBUTE PARALLEL DO SIMD ");
            },
            [&](const OmpLoopDirective::DistributeParallelDo &) {
              Word("DISTRIBUTE PARALLEL DO ");
            },
            [&](const OmpLoopDirective::DistributeSimd &) {
              Word("DISTRIBUTE SIMD ");
            },
            [&](const OmpLoopDirective::Distribute &) { Word("DISTRIBUTE "); },
            [&](const OmpLoopDirective::ParallelDoSimd &) {
              Word("PARALLEL DO SIMD ");
            },
            [&](const OmpLoopDirective::ParallelDo &) { Word("PARALLEL DO "); },
            [&](const OmpLoopDirective::Do &) { Word("DO "); },
            [&](const OmpLoopDirective::DoSimd &) { Word("Do SIMD "); },
            [&](const OmpLoopDirective::Simd &) { Word("SIMD "); },
            [&](const OmpLoopDirective::TargetParallelDoSimd &) {
              Word("TARGET PARALLEL DO SIMD ");
            },
            [&](const OmpLoopDirective::TargetParallelDo &) {
              Word("TARGET PARALLEL DO ");
            },
            [&](const OmpLoopDirective::TargetTeamsDistributeParallelDoSimd &) {
              Word("TARGET TEAMS DISTRIBUTE PARALLEL DO SIMD ");
            },
            [&](const OmpLoopDirective::TargetTeamsDistributeParallelDo &) {
              Word("TARGET TEAMS DISTRIBUTE PARALLEL DO ");
            },
            [&](const OmpLoopDirective::TargetTeamsDistributeSimd &) {
              Word("TARGET TEAMS DISTRIBUTE SIMD ");
            },
            [&](const OmpLoopDirective::TargetTeamsDistribute &) {
              Word("TARGET TEAMS DISTRIBUTE ");
            },
            [&](const OmpLoopDirective::TargetSimd &) { Word("TARGET SIMD "); },
            [&](const OmpLoopDirective::TaskloopSimd &) {
              Word("TASKLOOP SIMD ");
            },
            [&](const OmpLoopDirective::Taskloop &) { Word("TASKLOOP "); },
            [&](const OmpLoopDirective::TeamsDistributeParallelDoSimd &) {
              Word("TEAMS DISTRIBUTE PARALLEL DO SIMD ");
            },
            [&](const OmpLoopDirective::TeamsDistributeParallelDo &) {
              Word("TEAMS DISTRIBUTE PARALLEL DO ");
            },
            [&](const OmpLoopDirective::TeamsDistributeSimd &) {
              Word("TEAMS DISTRIBUTE SIMD ");
            },
            [&](const OmpLoopDirective::TeamsDistribute &) {
              Word("TEAMS DISTRIBUTE ");
            },
        },
        x.u);
  }
  void Unparse(const OmpObjectList &x) { Walk(x.v, ","); }
  void Unparse(const OmpStandaloneDirective &x) {
    std::visit(
        common::visitors{
            [&](const OmpStandaloneDirective::TargetEnterData &) {
              Word("TARGET ENTER DATA ");
            },
            [&](const OmpStandaloneDirective::TargetExitData &) {
              Word("TARGET EXIT DATA ");
            },
            [&](const OmpStandaloneDirective::TargetUpdate &) {
              Word("TARGET UPDATE ");
            },
        },
        x.u);
  }
  void Unparse(const OmpBlockDirective &x) {
    std::visit(
        common::visitors{
            [&](const OmpBlockDirective::Master &y) { Word("MASTER"); },
            [&](const OmpBlockDirective::Ordered &) { Word("ORDERED "); },
            [&](const OmpBlockDirective::ParallelWorkshare &) {
              Word("PARALLEL WORKSHARE ");
            },
            [&](const OmpBlockDirective::Parallel &) { Word("PARALLEL "); },
            [&](const OmpBlockDirective::TargetData &) {
              Word("TARGET DATA ");
            },
            [&](const OmpBlockDirective::TargetParallel &) {
              Word("TARGET PARALLEL ");
            },
            [&](const OmpBlockDirective::TargetTeams &) {
              Word("TARGET TEAMS ");
            },
            [&](const OmpBlockDirective::Target &) { Word("TARGET "); },
            [&](const OmpBlockDirective::Taskgroup &) { Word("TASKGROUP "); },
            [&](const OmpBlockDirective::Task &) { Word("TASK "); },
            [&](const OmpBlockDirective::Teams &) { Word("TEAMS "); },
        },
        x.u);
  }
  void Unparse(const OmpAtomic &x) {
    BeginOpenMP();
    Word("!$OMP ATOMIC");
    Walk(std::get<std::optional<OmpAtomic::SeqCst>>(x.t), " SEQ_CST");
    Put("\n");
    EndOpenMP();
    Walk(std::get<Statement<AssignmentStmt>>(x.t));
    BeginOpenMP();
    Walk(std::get<std::optional<OmpEndAtomic>>(x.t), "!$OMP END ATOMIC\n");
    EndOpenMP();
  }
  void Unparse(const OmpAtomicCapture &x) {
    BeginOpenMP();
    Word("!$OMP ATOMIC");
    Walk(std::get<std::optional<OmpAtomicCapture::SeqCst1>>(x.t), " SEQ_CST,");
    Word(" CAPTURE");
    Walk(std::get<std::optional<OmpAtomicCapture::SeqCst2>>(x.t), " ,SEQ_CST");
    Put("\n");
    EndOpenMP();
    Walk(std::get<OmpAtomicCapture::Stmt1>(x.t));
    Put("\n");
    Walk(std::get<OmpAtomicCapture::Stmt2>(x.t));
    BeginOpenMP();
    Word("!$OMP END ATOMIC\n");
    EndOpenMP();
  }
  void Unparse(const OmpAtomicRead &x) {
    BeginOpenMP();
    Word("!$OMP ATOMIC");
    Walk(std::get<std::optional<OmpAtomicRead::SeqCst1>>(x.t), " SEQ_CST,");
    Word(" READ");
    Walk(std::get<std::optional<OmpAtomicRead::SeqCst2>>(x.t), " ,SEQ_CST");
    Put("\n");
    EndOpenMP();
    Walk(std::get<Statement<AssignmentStmt>>(x.t));
    BeginOpenMP();
    Walk(std::get<std::optional<OmpEndAtomic>>(x.t), "!$OMP END ATOMIC\n");
    EndOpenMP();
  }
  void Unparse(const OmpAtomicUpdate &x) {
    BeginOpenMP();
    Word("!$OMP ATOMIC");
    Walk(std::get<std::optional<OmpAtomicUpdate::SeqCst1>>(x.t), " SEQ_CST,");
    Word(" UPDATE");
    Walk(std::get<std::optional<OmpAtomicUpdate::SeqCst2>>(x.t), " ,SEQ_CST");
    Put("\n");
    EndOpenMP();
    Walk(std::get<Statement<AssignmentStmt>>(x.t));
    BeginOpenMP();
    Walk(std::get<std::optional<OmpEndAtomic>>(x.t), "!$OMP END ATOMIC\n");
    EndOpenMP();
  }
  void Unparse(const OmpAtomicWrite &x) {
    BeginOpenMP();
    Word("!$OMP ATOMIC");
    Walk(std::get<std::optional<OmpAtomicWrite::SeqCst1>>(x.t), " SEQ_CST,");
    Word(" WRITE");
    Walk(std::get<std::optional<OmpAtomicWrite::SeqCst2>>(x.t), " ,SEQ_CST");
    Put("\n");
    EndOpenMP();
    Walk(std::get<Statement<AssignmentStmt>>(x.t));
    BeginOpenMP();
    Walk(std::get<std::optional<OmpEndAtomic>>(x.t), "!$OMP END ATOMIC\n");
    EndOpenMP();
  }
  void Unparse(const OmpEndCritical &x) {
    Walk(" (", x.v, ")");
    EndOpenMP();
  }
  void Unparse(const OpenMPCriticalConstruct &x) {
    BeginOpenMP();
    Word("!$OMP CRITICAL");
    Walk(" (", std::get<std::optional<Name>>(x.t), ")");
    Walk(" HINT(", std::get<std::optional<OpenMPCriticalConstruct::Hint>>(x.t),
        ")");
    Put("\n");
    EndOpenMP();
    Walk(std::get<Block>(x.t), "");
    BeginOpenMP();
    Word("!$OMP END CRITICAL");
    Walk(std::get<OmpEndCritical>(x.t));
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPDeclareTargetConstruct::WithClause &x) {
    Walk(x.maptype), Put("("), Walk(x.names), Put(")");
  }
  void Unparse(const OpenMPDeclareTargetConstruct::WithExtendedList &x) {
    Put("("), Walk(x.names), Put(")");
  }
  void Unparse(const OmpReductionInitializerClause &x) {
    Word(" INITIALIZER(OMP_PRIV = ");
    Walk(x.v);
    Put(")");
  }
  void Unparse(const OmpReductionCombiner::FunctionCombiner &x) {
    const auto &pd = std::get<ProcedureDesignator>(x.v.t);
    const auto &args = std::get<std::list<ActualArgSpec>>(x.v.t);
    Walk(pd);
    if (args.empty()) {
      if (std::holds_alternative<ProcComponentRef>(pd.u)) {
        Put("()");
      }
    } else {
      Walk("(", args, ", ", ")");
    }
  }
  void Unparse(const OpenMPDeclareReductionConstruct &x) {
    Put("(");
    Walk(std::get<OmpReductionOperator>(x.t)), Put(" : ");
    Walk(std::get<std::list<DeclarationTypeSpec>>(x.t), ","), Put(" : ");
    Walk(std::get<OmpReductionCombiner>(x.t));
    Put(")");
    Walk(std::get<std::optional<OmpReductionInitializerClause>>(x.t));
  }
  bool Pre(const OpenMPDeclarativeConstruct &x) {
    BeginOpenMP();
    Word("!$OMP ");
    return std::visit(
        common::visitors{
            [&](const OpenMPDeclareReductionConstruct &y) {
              Word("DECLARE REDUCTION ");
              return true;
            },
            [&](const OpenMPDeclareSimdConstruct &y) {
              Word("DECLARE SIMD ");
              Walk("(", std::get<std::optional<Name>>(y.t), ")");
              Walk(std::get<OmpClauseList>(y.t));
              Put("\n");
              EndOpenMP();
              return false;
            },
            [&](const OpenMPDeclareTargetConstruct &y) {
              Word("DECLARE TARGET ");
              return true;
            },
            [&](const OpenMPDeclarativeConstruct::Threadprivate &y) {
              Word("THREADPRIVATE (");
              return true;
            },
        },
        x.u);
  }
  void Post(const OpenMPDeclarativeConstruct &x) {
    Put("\n");
    EndOpenMP();
  }
  void Post(const OpenMPDeclarativeConstruct::Threadprivate &x) {
    Put(")\n");
    EndOpenMP();
  }
  void Unparse(const OmpEndDoSimd &x) {
    BeginOpenMP();
    Word("DO SIMD ");
    Walk(x.v);
    EndOpenMP();
  }
  void Unparse(const OmpEndDo &x) {
    BeginOpenMP();
    Word("DO ");
    Walk(x.v);
    EndOpenMP();
  }
  bool Pre(const OpenMPBarrierConstruct &x) {
    BeginOpenMP();
    Word("!$OMP BARRIER");
    Put("\n");
    EndOpenMP();
    return false;
  }
  void Unparse(const OpenMPSingleConstruct &x) {
    BeginOpenMP();
    Word("!$OMP SINGLE");
    Walk(std::get<OmpClauseList>(x.t));
    EndOpenMP();
    Put("\n");
    Walk(std::get<Block>(x.t), "");
    BeginOpenMP();
    Word("!$OMP END SINGLE ");
    Walk(std::get<OmpEndSingle>(x.t));
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OmpSection &x) {
    BeginOpenMP();
    Word("!$OMP SECTION");
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPSectionsConstruct &x) {
    BeginOpenMP();
    Word("!$OMP SECTIONS");
    Walk(std::get<OmpClauseList>(x.t));
    Put("\n");
    EndOpenMP();
    Walk(std::get<Block>(x.t), "");
    BeginOpenMP();
    Word("!$OMP END SECTIONS");
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPParallelSectionsConstruct &x) {
    BeginOpenMP();
    Word("!$OMP PARALLEL SECTIONS");
    Walk(std::get<OmpClauseList>(x.t));
    Put("\n");
    EndOpenMP();
    Walk(std::get<Block>(x.t), "");
    BeginOpenMP();
    Word("!$OMP END PARALLEL SECTIONS");
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPWorkshareConstruct &x) {
    BeginOpenMP();
    Word("!$OMP WORKSHARE");
    Put("\n");
    EndOpenMP();
    Walk(std::get<Block>(x.t), "");
    BeginOpenMP();
    Word("!$OMP END WORKSHARE ");
    Walk(std::get<std::optional<OmpNowait>>(x.t));
    Put("\n");
    EndOpenMP();
  }
  bool Pre(const OpenMPTaskyieldConstruct &x) {
    BeginOpenMP();
    Word("!$OMP TASKYIELD");
    Put("\n");
    EndOpenMP();
    return false;
  }
  bool Pre(const OpenMPTaskwaitConstruct &x) {
    BeginOpenMP();
    Word("!$OMP TASKWAIT");
    Put("\n");
    EndOpenMP();
    return false;
  }
  void Unparse(const OpenMPCancellationPointConstruct &x) {
    BeginOpenMP();
    Word("!$OMP CANCELLATION POINT ");
    Walk(x.v);
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPCancelConstruct &x) {
    BeginOpenMP();
    Word("!$OMP CANCEL ");
    Walk(std::get<OmpCancelType>(x.t));
    Walk(std::get<std::optional<OpenMPCancelConstruct::If>>(x.t));
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPFlushConstruct &x) {
    BeginOpenMP();
    Word("!$OMP FLUSH");
    if ((x.v).has_value()) {
      Put("(");
      Walk(x.v);
      Put(")");
    }
    Put("\n");
    EndOpenMP();
  }
  bool Pre(const OpenMPEndLoopDirective &x) {
    BeginOpenMP();
    Word("!$OMP END ");
    return true;
  }
  void Post(const OpenMPEndLoopDirective &x) {
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OmpClauseList &x) { Walk(" ", x.v, " "); }
  void Unparse(const OpenMPStandaloneConstruct &x) {
    BeginOpenMP();
    Word("!$OMP ");
    Walk(std::get<OmpStandaloneDirective>(x.t));
    Walk(std::get<OmpClauseList>(x.t));
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPBlockConstruct &x) {
    BeginOpenMP();
    Word("!$OMP ");
    Walk(std::get<OmpBlockDirective>(x.t));
    Walk(std::get<OmpClauseList>(x.t));
    Put("\n");
    EndOpenMP();
    Walk(std::get<Block>(x.t), "");
    BeginOpenMP();
    Word("!$OMP END ");
    Walk(std::get<OmpEndBlockDirective>(x.t));
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const OpenMPLoopConstruct &x) {
    BeginOpenMP();
    Word("!$OMP ");
    Walk(std::get<OmpLoopDirective>(x.t));
    Walk(std::get<OmpClauseList>(x.t));
    Put("\n");
    EndOpenMP();
  }
  void Unparse(const BasedPointerStmt &x) {
    Word("POINTER ("), Walk(std::get<0>(x.t)), Put(", ");
    Walk(std::get<1>(x.t));
    Walk("(", std::get<std::optional<ArraySpec>>(x.t), ")"), Put(')');
  }
  void Post(const StructureField &x) {
    if (const auto *def{std::get_if<Statement<DataComponentDefStmt>>(&x.u)}) {
      for (const auto &decl :
          std::get<std::list<ComponentDecl>>(def->statement.t)) {
        structureComponents_.insert(std::get<Name>(decl.t).source);
      }
    }
  }
  void Unparse(const StructureStmt &x) {
    Word("STRUCTURE ");
    if (std::get<bool>(x.t)) {  // slashes around name
      Put('/'), Walk(std::get<Name>(x.t)), Put('/');
      Walk(" ", std::get<std::list<EntityDecl>>(x.t), ", ");
    } else {
      CHECK(std::get<std::list<EntityDecl>>(x.t).empty());
      Walk(std::get<Name>(x.t));
    }
    Indent();
  }
  void Post(const Union::UnionStmt &) { Word("UNION"), Indent(); }
  void Post(const Union::EndUnionStmt &) { Outdent(), Word("END UNION"); }
  void Post(const Map::MapStmt &) { Word("MAP"), Indent(); }
  void Post(const Map::EndMapStmt &) { Outdent(), Word("END MAP"); }
  void Post(const StructureDef::EndStructureStmt &) {
    Outdent(), Word("END STRUCTURE");
  }
  void Unparse(const OldParameterStmt &x) {
    Word("PARAMETER "), Walk(x.v, ", ");
  }
  void Unparse(const ArithmeticIfStmt &x) {
    Word("IF ("), Walk(std::get<Expr>(x.t)), Put(") ");
    Walk(std::get<1>(x.t)), Put(", ");
    Walk(std::get<2>(x.t)), Put(", ");
    Walk(std::get<3>(x.t));
  }
  void Unparse(const AssignStmt &x) {
    Word("ASSIGN "), Walk(std::get<Label>(x.t));
    Word(" TO "), Walk(std::get<Name>(x.t));
  }
  void Unparse(const AssignedGotoStmt &x) {
    Word("GO TO "), Walk(std::get<Name>(x.t));
    Walk(", (", std::get<std::list<Label>>(x.t), ", ", ")");
  }
  void Unparse(const PauseStmt &x) { Word("PAUSE"), Walk(" ", x.v); }

#define WALK_NESTED_ENUM(CLASS, ENUM) \
  void Unparse(const CLASS::ENUM &x) { Word(CLASS::EnumToString(x)); }
  WALK_NESTED_ENUM(AccessSpec, Kind)  // R807
  WALK_NESTED_ENUM(common, TypeParamAttr)  // R734
  WALK_NESTED_ENUM(IntentSpec, Intent)  // R826
  WALK_NESTED_ENUM(ImplicitStmt, ImplicitNoneNameSpec)  // R866
  WALK_NESTED_ENUM(ConnectSpec::CharExpr, Kind)  // R1205
  WALK_NESTED_ENUM(IoControlSpec::CharExpr, Kind)
  WALK_NESTED_ENUM(InquireSpec::CharVar, Kind)
  WALK_NESTED_ENUM(InquireSpec::IntVar, Kind)
  WALK_NESTED_ENUM(InquireSpec::LogVar, Kind)
  WALK_NESTED_ENUM(ProcedureStmt, Kind)  // R1506
  WALK_NESTED_ENUM(UseStmt, ModuleNature)  // R1410
  WALK_NESTED_ENUM(OmpProcBindClause, Type)  // OMP PROC_BIND
  WALK_NESTED_ENUM(OmpDefaultClause, Type)  // OMP DEFAULT
  WALK_NESTED_ENUM(OmpScheduleModifierType, ModType)  // OMP schedule-modifier
  WALK_NESTED_ENUM(OmpLinearModifier, Type)  // OMP linear-modifier
  WALK_NESTED_ENUM(OmpDependenceType, Type)  // OMP dependence-type
  WALK_NESTED_ENUM(OmpMapType, Type)  // OMP map-type
  WALK_NESTED_ENUM(OmpScheduleClause, ScheduleType)  // OMP schedule-type
  WALK_NESTED_ENUM(
      OmpIfClause, DirectiveNameModifier)  // OMP directive-modifier
  WALK_NESTED_ENUM(OmpDeclareTargetMapType, Type)  // OMP DeclareTarget map-type
  WALK_NESTED_ENUM(OmpCancelType, Type)  // OMP cancel-type
#undef WALK_NESTED_ENUM

  void Done() const { CHECK(indent_ == 0); }

private:
  void Put(char);
  void Put(const char *);
  void Put(const std::string &);
  void PutKeywordLetter(char);
  void Word(const char *);
  void Word(const std::string &);
  void Indent() { indent_ += indentationAmount_; }
  void Outdent() {
    CHECK(indent_ >= indentationAmount_);
    indent_ -= indentationAmount_;
  }
  void BeginOpenMP() { openmpDirective_ = true; }
  void EndOpenMP() { openmpDirective_ = false; }

  // Call back to the traversal framework.
  template<typename T> void Walk(const T &x) {
    Fortran::parser::Walk(x, *this);
  }

  // Traverse a std::optional<> value.  Emit a prefix and/or a suffix string
  // only when it contains a value.
  template<typename A>
  void Walk(
      const char *prefix, const std::optional<A> &x, const char *suffix = "") {
    if (x.has_value()) {
      Word(prefix), Walk(*x), Word(suffix);
    }
  }
  template<typename A>
  void Walk(const std::optional<A> &x, const char *suffix = "") {
    return Walk("", x, suffix);
  }

  // Traverse a std::list<>.  Separate the elements with an optional string.
  // Emit a prefix and/or a suffix string only when the list is not empty.
  template<typename A>
  void Walk(const char *prefix, const std::list<A> &list,
      const char *comma = ", ", const char *suffix = "") {
    if (!list.empty()) {
      const char *str{prefix};
      for (const auto &x : list) {
        Word(str), Walk(x);
        str = comma;
      }
      Word(suffix);
    }
  }
  template<typename A>
  void Walk(const std::list<A> &list, const char *comma = ", ",
      const char *suffix = "") {
    return Walk("", list, comma, suffix);
  }

  // Traverse a std::tuple<>, with an optional separator.
  template<std::size_t J = 0, typename T>
  void WalkTupleElements(const T &tuple, const char *separator) {
    if constexpr (J < std::tuple_size_v<T>) {
      if (J > 0) {
        Word(separator);
      }
      Walk(std::get<J>(tuple));
      WalkTupleElements<J + 1>(tuple, separator);
    }
  }
  template<typename... A>
  void Walk(const std::tuple<A...> &tuple, const char *separator = "") {
    WalkTupleElements(tuple, separator);
  }

  void EndSubprogram(const char *kind, const std::optional<Name> &name) {
    Outdent(), Word("END "), Word(kind), Walk(" ", name);
    structureComponents_.clear();
  }

  std::ostream &out_;
  int indent_{0};
  const int indentationAmount_{1};
  int column_{1};
  const int maxColumns_{80};
  std::set<CharBlock> structureComponents_;
  Encoding encoding_{Encoding::UTF8};
  bool capitalizeKeywords_{true};
  bool openmpDirective_{false};
  bool backslashEscapes_{false};
  preStatementType *preStatement_{nullptr};
};

void UnparseVisitor::Put(char ch) {
  int sav = indent_;
  if (openmpDirective_) {
    indent_ = 0;
  }
  if (column_ <= 1) {
    if (ch == '\n') {
      return;
    }
    for (int j{0}; j < indent_; ++j) {
      out_ << ' ';
    }
    column_ = indent_ + 2;
  } else if (ch == '\n') {
    column_ = 1;
  } else if (++column_ >= maxColumns_) {
    out_ << "&\n";
    for (int j{0}; j < indent_; ++j) {
      out_ << ' ';
    }
    if (openmpDirective_) {
      out_ << "!$OMP&";
      column_ = 8;
    } else {
      out_ << '&';
      column_ = indent_ + 3;
    }
  }
  out_ << ch;
  if (openmpDirective_) {
    indent_ = sav;
  }
}

void UnparseVisitor::Put(const char *str) {
  for (; *str != '\0'; ++str) {
    Put(*str);
  }
}

void UnparseVisitor::Put(const std::string &str) {
  for (char ch : str) {
    Put(ch);
  }
}

void UnparseVisitor::PutKeywordLetter(char ch) {
  if (capitalizeKeywords_) {
    Put(ToUpperCaseLetter(ch));
  } else {
    Put(ToLowerCaseLetter(ch));
  }
}

void UnparseVisitor::Word(const char *str) {
  for (; *str != '\0'; ++str) {
    PutKeywordLetter(*str);
  }
}

void UnparseVisitor::Word(const std::string &str) { Word(str.c_str()); }

void Unparse(std::ostream &out, const Program &program, Encoding encoding,
    bool capitalizeKeywords, bool backslashEscapes,
    preStatementType *preStatement) {
  UnparseVisitor visitor{
      out, 1, encoding, capitalizeKeywords, backslashEscapes, preStatement};
  Walk(program, visitor);
  visitor.Done();
}
}