From de7f4b14f5a8b359eb410bcb38b1e582f51b88d8 Mon Sep 17 00:00:00 2001
From: Roberto Raggi <roberto.raggi@gmail.com>
Date: Wed, 16 Jul 2025 19:43:05 +0200
Subject: [PATCH] Disallow nested structs and enums in C mode

Fixes #565

Signed-off-by: Roberto Raggi <roberto.raggi@gmail.com>
---
 src/parser/cxx/parser.cc            | 23 ++++++++++------
 src/parser/cxx/parser.h             |  2 ++
 src/parser/cxx/scope.cc             |  4 +++
 src/parser/cxx/scope.h              |  1 +
 src/parser/cxx/symbol_printer.cc    |  5 +++-
 tests/unit_tests/sema/struct_c_01.c | 41 +++++++++++++++++++++++++++++
 6 files changed, 67 insertions(+), 9 deletions(-)
 create mode 100644 tests/unit_tests/sema/struct_c_01.c

diff --git a/src/parser/cxx/parser.cc b/src/parser/cxx/parser.cc
index 069635b1..3ac09605 100644
--- a/src/parser/cxx/parser.cc
+++ b/src/parser/cxx/parser.cc
@@ -5206,11 +5206,6 @@ auto Parser::parse_elaborated_enum_specifier(SpecifierAST*& yyast,
   SourceLocation enumLoc;
   if (!match(TokenKind::T_ENUM, enumLoc)) return false;
 
-  auto globalScopeGuard = Binder::ScopeGuard{&binder_};
-  if (is_parsing_c()) {
-    setScope(globalScope_);
-  }
-
   NestedNameSpecifierAST* nestedNameSpecifier = nullptr;
   parse_optional_nested_name_specifier(
       nestedNameSpecifier, NestedNameSpecifierContext::kDeclarative);
@@ -5251,8 +5246,9 @@ auto Parser::parse_elaborated_type_specifier(SpecifierAST*& yyast,
   if (!parse_class_key(classLoc)) return false;
 
   auto globalScopeGuard = Binder::ScopeGuard{&binder_};
+
   if (is_parsing_c()) {
-    setScope(globalScope_);
+    setScope(getCurrentNonClassScope());
   }
 
   List<AttributeSpecifierAST*>* attributes = nullptr;
@@ -6408,8 +6404,9 @@ auto Parser::parse_enum_specifier(SpecifierAST*& yyast, DeclSpecs& specs)
   if (!parse_enum_key(enumLoc, classLoc)) return false;
 
   auto globalScopeGuard = Binder::ScopeGuard{&binder_};
+
   if (is_parsing_c()) {
-    setScope(globalScope_);
+    setScope(getCurrentNonClassScope());
   }
 
   List<AttributeSpecifierAST*>* attributes = nullptr;
@@ -7700,8 +7697,9 @@ auto Parser::parse_class_specifier(ClassSpecifierAST*& yyast, DeclSpecs& specs)
   if (!parse_class_key(classLoc)) return false;
 
   auto globalScopeGuard = Binder::ScopeGuard{&binder_};
+
   if (is_parsing_c()) {
-    setScope(globalScope_);
+    setScope(getCurrentNonClassScope());
   }
 
   List<AttributeSpecifierAST*>* attributeList = nullptr;
@@ -9634,6 +9632,15 @@ void Parser::completePendingFunctionDefinitions() {
   }
 }
 
+auto Parser::getCurrentNonClassScope() const -> Scope* {
+  for (auto current = scope(); current; current = current->parent()) {
+    if (current->isClassOrNamespaceScope()) continue;
+    return current;
+  }
+
+  return globalScope_;
+}
+
 auto Parser::scope() const -> Scope* { return binder_.scope(); }
 
 void Parser::setScope(Scope* scope) { binder_.setScope(scope); }
diff --git a/src/parser/cxx/parser.h b/src/parser/cxx/parser.h
index 01a43d34..8c64b6d7 100644
--- a/src/parser/cxx/parser.h
+++ b/src/parser/cxx/parser.h
@@ -780,6 +780,8 @@ class Parser final {
   void completePendingFunctionDefinitions();
   void completeFunctionDefinition(FunctionDefinitionAST* ast);
 
+  [[nodiscard]] auto getCurrentNonClassScope() const -> Scope*;
+
   [[nodiscard]] auto scope() const -> Scope*;
   void setScope(Scope* scope);
   void setScope(ScopedSymbol* symbol);
diff --git a/src/parser/cxx/scope.cc b/src/parser/cxx/scope.cc
index c243dead..e22b6834 100644
--- a/src/parser/cxx/scope.cc
+++ b/src/parser/cxx/scope.cc
@@ -74,6 +74,10 @@ auto Scope::isTemplateParametersScope() const -> bool {
   return owner_ && owner_->isTemplateParameters();
 }
 
+auto Scope::isFunctionParametersScope() const -> bool {
+  return owner_ && owner_->isFunctionParameters();
+}
+
 auto Scope::enclosingNamespaceScope() const -> Scope* {
   for (auto scope = parent_; scope; scope = scope->parent()) {
     if (scope->isNamespaceScope()) {
diff --git a/src/parser/cxx/scope.h b/src/parser/cxx/scope.h
index 91715052..bb65462a 100644
--- a/src/parser/cxx/scope.h
+++ b/src/parser/cxx/scope.h
@@ -46,6 +46,7 @@ class Scope {
   [[nodiscard]] auto isBlockScope() const -> bool;
   [[nodiscard]] auto isEnumScope() const -> bool;
   [[nodiscard]] auto isTemplateParametersScope() const -> bool;
+  [[nodiscard]] auto isFunctionParametersScope() const -> bool;
 
   [[nodiscard]] auto enclosingNamespaceScope() const -> Scope*;
   [[nodiscard]] auto enclosingNonTemplateParametersScope() const -> Scope*;
diff --git a/src/parser/cxx/symbol_printer.cc b/src/parser/cxx/symbol_printer.cc
index a9eda6a1..ae438057 100644
--- a/src/parser/cxx/symbol_printer.cc
+++ b/src/parser/cxx/symbol_printer.cc
@@ -70,7 +70,10 @@ struct DumpSymbols {
 
   void operator()(NamespaceSymbol* symbol) {
     indent();
-    out << std::format("namespace {}\n", to_string(symbol->name()));
+    out << "namespace";
+    if (symbol->name())
+      out << std::format(" {}", to_string(symbol->name()));
+    out << "\n";
     dumpScope(symbol->scope());
   }
 
diff --git a/tests/unit_tests/sema/struct_c_01.c b/tests/unit_tests/sema/struct_c_01.c
new file mode 100644
index 00000000..8118599b
--- /dev/null
+++ b/tests/unit_tests/sema/struct_c_01.c
@@ -0,0 +1,41 @@
+// RUN: %cxx -fcheck -dump-symbols -xc %s | %filecheck %s --match-full-lines
+
+enum E {
+  v,
+};
+
+struct A {
+  enum E e;
+  int x;
+};
+
+int main() {
+  enum K {
+    w,
+  };
+
+  struct B {
+    enum K k;
+    enum E e;
+    int y;
+  };
+
+  struct M;
+}
+
+// clang-format off
+//      CHECK:namespace
+// CHECK-NEXT:  enum E : int
+// CHECK-NEXT:  enumerator E v
+// CHECK-NEXT:  class A
+// CHECK-NEXT:    field E e
+// CHECK-NEXT:    field int x
+// CHECK-NEXT:  function int main()
+// CHECK-NEXT:    block
+// CHECK-NEXT:      enum K : int
+// CHECK-NEXT:      enumerator K w
+// CHECK-NEXT:      class B
+// CHECK-NEXT:        field K k
+// CHECK-NEXT:        field E e
+// CHECK-NEXT:        field int y
+// CHECK-NEXT:      class M