Add codegen support for destructible lambdas

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -592,6 +592,14 @@ void Converter::EmitScopedDestructor(const clang::VarDecl *decl) {
     return;
   }
   auto type = decl->getType();
+  if (auto lambda = AsLambdaClass(type);
+      lambda && LambdaNeedsDestruction(lambda)) {
+    StrCat(token::kSemiColon,
+           std::format("let _dtor_{0} = ScopedDestructorUnsafe::new(&raw mut "
+                       "{0}, |__f| __f.destroy())",
+                       GetNamedDeclAsString(decl)));
+    return;
+  }
   if (type->isReferenceType() || type->isArrayType() ||
       !TypeNeedsDestruction(type)) {
     return;
@@ -3865,6 +3873,11 @@ bool Converter::VisitLambdaExpr(clang::LambdaExpr *expr) {
   StrCat(token::kComma);
   ConvertLambdaClosure(decl);
   ConvertLambdaCopyAndMove(decl);
+  if (LambdaNeedsDestruction(decl)) {
+    StrCat(token::kComma, "destroy", token::kAssign);
+    PushBrace destroy(*this);
+    StrCat(DestroyMembers(decl));
+  }
   computed_expr_type_ = ComputedExprType::FreshValue;
   return false;
 }

cpp2rust/converter/converter_lib.cpp

@@ -1088,6 +1088,12 @@ bool IsLambdaCopyOrMoveConstructor(const clang::CXXConstructorDecl *ctor) {
          !decl->captures().empty();
 }
 
+bool LambdaNeedsDestruction(const clang::CXXRecordDecl *decl) {
+  return llvm::any_of(decl->fields(), [](const clang::FieldDecl *field) {
+    return TypeNeedsDestruction(field->getType());
+  });
+}
+
 clang::Expr *AsLambdaUncapturedConstant(const clang::FunctionDecl *fn,
                                         clang::DeclRefExpr *expr) {
   if (!AsLambdaOperatorCall(fn)) {

cpp2rust/converter/converter_lib.h

@@ -206,6 +206,8 @@ const clang::LambdaCapture *AsLambdaCapture(const clang::FieldDecl *field);
 
 bool IsLambdaCopyOrMoveConstructor(const clang::CXXConstructorDecl *ctor);
 
+bool LambdaNeedsDestruction(const clang::CXXRecordDecl *decl);
+
 clang::Expr *AsLambdaUncapturedConstant(const clang::FunctionDecl *fn,
                                         clang::DeclRefExpr *expr);
 

cpp2rust/converter/models/converter_refcount.cpp

@@ -873,6 +873,14 @@ void ConverterRefCount::EmitScopedDestructor(const clang::VarDecl *decl) {
     return;
   }
   auto type = decl->getType();
+  if (auto lambda = AsLambdaClass(type);
+      lambda && LambdaNeedsDestruction(lambda)) {
+    StrCat(token::kSemiColon,
+           std::format("let _dtor_{0} = ScopedDestructor::new(&{0}, |__p| "
+                       "__p.with(|__f| __f.destroy()))",
+                       GetNamedDeclAsString(decl)));
+    return;
+  }
   if (type->isReferenceType() || type->isArrayType() ||
       !TypeNeedsDestruction(type)) {
     return;
@@ -3423,6 +3431,12 @@ ConverterRefCount::DestroyMembers(const clang::CXXRecordDecl *decl) {
   std::string out;
   for (auto *field : std::ranges::reverse_view(fields)) {
     auto name = GetNamedDeclAsString(field);
+    if (decl->isLambda()) {
+      assert(!field->getType()->isArrayType());
+      out +=
+          std::format("self.{0}.as_pointer().{1}();\n", name, kDestructorName);
+      continue;
+    }
     if (field->getType()->isArrayType()) {
       auto *elem =
           field->getType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();