chore: Add views over AST lists

packages/cxx-gen-ast/src/gen_ast_dump_cc.ts

@@ -42,8 +42,8 @@ export function gen_ast_dump_cc({ ast, output }: { ast: AST; output: string }) {
       emit(`    ++indent_;`);
       emit(`    out_ << std::format("{:{}}", "", indent_ * 2);`);
       emit(`    out_ << std::format("{}\\n", "${fieldName}");`);
-      emit(`    for (auto it = ast->${member.name}; it; it = it->next) {`);
-      emit(`      accept(it->value);`);
+      emit(`    for (auto node: ListView{ast->${member.name}}) {`);
+      emit(`      accept(node);`);
       emit(`    }`);
       emit(`    --indent_;`);
       emit(`  }`);

packages/cxx-gen-ast/src/gen_ast_encoder_cc.ts

@@ -114,9 +114,9 @@ export function gen_ast_encoder_cc({
           const className = makeClassName(m.type);
           emit(`  std::vector<flatbuffers::Offset<io::${className}>>`);
           emit(`    ${m.name}Offsets;`);
-          emit(`  for (auto it = ast->${m.name}; it; it = it->next) {`);
-          emit(`     if (!it->value) continue;`);
-          emit(`     ${m.name}Offsets.emplace_back(accept(it->value).o);`);
+          emit(`  for (auto node : ListView{ast->${m.name}}) {`);
+          emit(`     if (!node) continue;`);
+          emit(`     ${m.name}Offsets.emplace_back(accept(node).o);`);
           emit(`  }`);
           emit();
           emit(`  auto ${m.name}OffsetsVector = fbb_.CreateVector(`);
@@ -130,10 +130,10 @@ export function gen_ast_encoder_cc({
           emit(`  std::vector<std::underlying_type_t<io::${className}>>`);
           emit(`    ${m.name}Types;`);
           emit();
-          emit(`  for (auto it = ast->${m.name}; it; it = it->next) {`);
-          emit(`    if (!it->value) continue;`);
+          emit(`  for (auto node : ListView{ast->${m.name}}) {`);
+          emit(`    if (!node) continue;`);
           emit(`    const auto [offset, type] = accept${className}(`);
-          emit(`      it->value);`);
+          emit(`      node);`);
           emit(`    ${m.name}Offsets.push_back(offset);`);
           emit(`    ${m.name}Types.push_back(type);`);
           emit(`  }`);

packages/cxx-gen-ast/src/gen_ast_h.ts

@@ -90,7 +90,7 @@ export function gen_ast_h({ ast, output }: { ast: AST; output: string }) {
       }
 
       emit(
-        `  void accept(ASTVisitor* visitor) override { visitor->visit(this); }`,
+        `  void accept(ASTVisitor* visitor) override { visitor->visit(this); }`
       );
       emit();
       emit(`  auto firstSourceLocation() -> SourceLocation override;`);
@@ -110,7 +110,7 @@ export function gen_ast_h({ ast, output }: { ast: AST; output: string }) {
     emit(`  switch (ast->kind()) {`);
     nodes.forEach(({ name }) => {
       emit(
-        `  case ${name}::Kind: return std::invoke(std::forward<Visitor>(visitor), static_cast<${name}*>(ast));`,
+        `  case ${name}::Kind: return std::invoke(std::forward<Visitor>(visitor), static_cast<${name}*>(ast));`
       );
     });
     emit(`    default: cxx_runtime_error("unexpected ${variantName}");`);
@@ -130,35 +130,76 @@ export function gen_ast_h({ ast, output }: { ast: AST; output: string }) {
 #include <cxx/const_value.h>
 #include <cxx/symbols_fwd.h>
 #include <optional>
+#include <ranges>
 
 namespace cxx {
 
 template <typename T>
 class List final : public Managed {
 public:
-    T value;
-    List* next;
+  T value;
+  List* next;
 
-    explicit List(const T& value, List* next = nullptr)
-        : value(value), next(next) {}
+  explicit List(const T& value, List* next = nullptr)
+      : value(value), next(next) {}
+};
+
+template <typename T>
+class ListIterator {
+ public:
+  using value_type = T;
+  using difference_type = std::ptrdiff_t;
+
+  ListIterator() = default;
+  explicit ListIterator(List<T>* list) : list_(list) {}
+
+  auto operator<=>(const ListIterator&) const = default;
+
+  auto operator*() const -> const T& { return list_->value; }
+
+  auto operator++() -> ListIterator& {
+    list_ = list_->next;
+    return *this;
+  }
+
+  auto operator++(int) -> ListIterator {
+    auto it = *this;
+    ++*this;
+    return it;
+  }
+
+ private:
+  List<T>* list_{};
+};
+
+template <typename T>
+class ListView : std::ranges::view_interface<ListView<T>> {
+ public:
+  explicit ListView(List<T>* list) : list_(list) {}
+
+  auto begin() const { return ListIterator<T>(list_); }
+  auto end() const { return ListIterator<T>(); }
+
+ private:
+  List<T>* list_;
 };
 
 class AST : public Managed {
 public:
-    explicit AST(ASTKind kind): kind_(kind) {}
+  explicit AST(ASTKind kind): kind_(kind) {}
 
-    virtual ~AST();
+  virtual ~AST();
 
-    [[nodiscard]] auto kind() const -> ASTKind { return kind_; }
+  [[nodiscard]] auto kind() const -> ASTKind { return kind_; }
 
-    virtual void accept(ASTVisitor* visitor) = 0;
+  virtual void accept(ASTVisitor* visitor) = 0;
 
-    virtual auto firstSourceLocation() -> SourceLocation = 0;
-    virtual auto lastSourceLocation() -> SourceLocation = 0;
+  virtual auto firstSourceLocation() -> SourceLocation = 0;
+  virtual auto lastSourceLocation() -> SourceLocation = 0;
 
-    [[nodiscard]] auto sourceLocationRange() -> SourceLocationRange {
-        return SourceLocationRange(firstSourceLocation(), lastSourceLocation());
-    }
+  [[nodiscard]] auto sourceLocationRange() -> SourceLocationRange {
+      return SourceLocationRange(firstSourceLocation(), lastSourceLocation());
+  }
 
 private:
     ASTKind kind_;
@@ -173,8 +214,8 @@ template <typename T>
 
 template <typename T>
 [[nodiscard]] inline auto firstSourceLocation(List<T>* nodes) -> SourceLocation {
-    for (auto it = nodes; it; it = it->next) {
-        if (auto loc = firstSourceLocation(it->value)) return loc;
+    for (auto node : ListView{nodes}) {
+        if (auto loc = firstSourceLocation(node)) return loc;
     }
     return {};
 }

packages/cxx-gen-ast/src/new_ast_op_cc.ts

@@ -69,8 +69,8 @@ export function new_ast_op_cc({
         }
         case "node-list": {
           emit();
-          emit(`  for (auto it = ast->${m.name}; it; it = it->next) {`);
-          emit(`    auto value = operator()(it->value);`);
+          emit(`  for (auto node : ListView{ast->${m.name}}) {`);
+          emit(`    auto value = operator()(node);`);
           emit(`  }`);
           emit();
           break;
@@ -90,7 +90,7 @@ export function new_ast_op_cc({
       const resultTy = `${chopAST(base)}Result`;
       emit();
       emit(
-        `auto ${opName}::${className}Visitor::operator()(${name}* ast) -> ${resultTy} {`,
+        `auto ${opName}::${className}Visitor::operator()(${name}* ast) -> ${resultTy} {`
       );
       members.forEach((m) => {
         switch (m.kind) {
@@ -100,8 +100,8 @@ export function new_ast_op_cc({
           }
           case "node-list": {
             emit();
-            emit(`  for (auto it = ast->${m.name}; it; it = it->next) {`);
-            emit(`    auto value = accept(it->value);`);
+            emit(`  for (auto node : ListView{ast->${m.name}}) {`);
+            emit(`    auto value = accept(node);`);
             emit(`  }`);
             emit();
             break;

packages/cxx-gen-ast/src/new_ast_rewriter_cc.ts

@@ -63,7 +63,7 @@ export function new_ast_rewriter_cc({
             emit(`  copy->${m.name} = ${visitor}(ast->${m.name});`);
           } else {
             emit(
-              `  copy->${m.name} = ast_cast<${m.type}>(${visitor}(ast->${m.name}));`,
+              `  copy->${m.name} = ast_cast<${m.type}>(${visitor}(ast->${m.name}));`
             );
           }
           break;
@@ -72,8 +72,8 @@ export function new_ast_rewriter_cc({
           emit();
           emit(`  if (auto it = ast->${m.name}) {`);
           emit(`    auto out = &copy->${m.name};`);
-          emit(`    for (auto it = ast->${m.name}; it; it = it->next) {`);
-          emit(`        auto value = ${visitor}(it->value);`);
+          emit(`    for (auto node : ListView{ast->${m.name}}) {`);
+          emit(`        auto value = ${visitor}(node);`);
           if (isBase(m.type)) {
             emit(`*out = new (arena()) List(value);`);
           } else {
@@ -126,7 +126,7 @@ export function new_ast_rewriter_cc({
     nodes.forEach(({ name, members }) => {
       emit();
       emit(
-        `auto ${opName}::${className}Visitor::operator()(${name}* ast) -> ${base}* {`,
+        `auto ${opName}::${className}Visitor::operator()(${name}* ast) -> ${base}* {`
       );
       emit(`  auto copy = new (arena()) ${name}{};`);
       emit();