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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Incorrect substitutions for rules using `Ptr` parameters","articleBody":"Using the following rules for `std::vector`:\n```cpp\n// src.cpp\ntemplate \u003ctypename T1\u003e using t1 = std::vector\u003cT1\u003e;\n\ntemplate \u003ctypename T1\u003e std::vector\u003cT1\u003e f1(const std::vector\u003cT1\u003e \u0026a0) {\n  return std::vector\u003cT1\u003e(a0);\n}\n\ntemplate \u003ctypename T1\u003e std::vector\u003cT1\u003e f2(std::vector\u003cT1\u003e \u0026\u0026a0) {\n  return std::vector\u003cT1\u003e(std::move(a0));\n}\n\ntemplate \u003ctypename T1\u003e\nstd::vector\u003cT1\u003e \u0026f3(std::vector\u003cT1\u003e \u0026a0, std::vector\u003cT1\u003e \u0026\u0026a1) {\n  return a0.operator=(std::move(a1));\n}\n```\n```rust\n// tgt_refcount.rs\nfn t1\u003cT1\u003e() -\u003e Vec\u003cT1\u003e {\n    Vec::new()\n}\n\nfn f1\u003cT1: Clone\u003e(a0: Ptr\u003cVec\u003cT1\u003e\u003e) -\u003e Vec\u003cT1\u003e {\n    a0.to_strong().borrow().clone()\n}\n\nfn f2\u003cT1\u003e(a0: Ptr\u003cVec\u003cT1\u003e\u003e) -\u003e Vec\u003cT1\u003e {\n    std::mem::take(\u0026mut *a0.to_strong().borrow_mut())\n}\n\nfn f3\u003cT1: ByteRepr\u003e(a0: Ptr\u003cVec\u003cT1\u003e\u003e, a1: Ptr\u003cVec\u003cT1\u003e\u003e) -\u003e Ptr\u003cVec\u003cT1\u003e\u003e {\n    let moved = a1.with_mut(|v| std::mem::take(v));\n    a0.with_mut(|dst| *dst = moved);\n    a0\n}\n```\n\nThe following translation is generated:\n```cpp\nint main() {\n  std::vector\u003cint\u003e vec1;\n  std::vector\u003cint\u003e vec2(std::move(vec1));\n  std::vector\u003cint\u003e vec3(vec2);\n  vec3 = std::move(vec2);\n\n  return 0;\n}\n```\n```rust\nfn main_0() -\u003e i32 {\n    let vec1: Value\u003cVec\u003ci32\u003e\u003e = Rc::new(RefCell::new(Vec::new()));\n    let vec2: Value\u003cVec\u003ci32\u003e\u003e = Rc::new(RefCell::new(std::mem::take(\n        \u0026mut *(*vec1.borrow_mut()).to_strong().borrow_mut(), // (*vec1.borrow_mut()) should be (vec1.as_pointer() as Ptr\u003c...\u003e)\n    )));\n    let vec3: Value\u003cVec\u003ci32\u003e\u003e =\n        Rc::new(RefCell::new(vec2.as_pointer().to_strong().borrow().clone())); // vec2.as_pointer should be (vec2.as_pointer() as Ptr\u003c...\u003e)\n    {\n        let moved = (*vec2.borrow_mut()).with_mut(|v| std::mem::take(v)); // (*vec2.borrow_mut()) should be (vec2.as_pointer() as Ptr\u003c...\u003e)\n        (vec3.as_pointer() as Ptr\u003cVec\u003ci32\u003e\u003e).with_mut(|dst| *dst = moved);\n        (vec3.as_pointer() as Ptr\u003cVec\u003ci32\u003e\u003e)\n    };\n    return 0;\n}\n```\n\nThe generated `ir_refcount.json` appears to be correct. All `Ptr` parameters are marked as `is_refcount_pointer`:\n```json\n// f1\n\"params\": {\n  \"a0\": {\n    \"type\": \"Ptr\u003cVec\u003cT1\u003e\u003e\",\n    \"is_refcount_pointer\": true\n  }\n},\n\n// f2\n\"params\": {\n  \"a0\": {\n    \"type\": \"Ptr\u003cVec\u003cT1\u003e\u003e\",\n    \"is_refcount_pointer\": true\n    }\n},\n\n// f3\n\"params\": {\n  \"a0\": {\n    \"type\": \"Ptr\u003cVec\u003cT1\u003e\u003e\",\n    \"is_refcount_pointer\": true\n  },\n  \"a1\": {\n    \"type\": \"Ptr\u003cVec\u003cT1\u003e\u003e\",\n    \"is_refcount_pointer\": true\n  }\n},\n```","author":{"url":"https://github.com/joaotgouveia","@type":"Person","name":"joaotgouveia"},"datePublished":"2026-07-01T12:04:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/220/cpp2rust/issues/220"}