[jira] [Updated] (THRIFT-6058) Rust codegen: `list` deserialization generates shadowed variable and missing Box wrapping

["Santiago Medina (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/THRIFT-6058?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Santiago Medina updated THRIFT-6058:
------------------------------------
    Description:     (was: The Rust code generator produces incorrect deserialization code for `list<UnionType>` and `set<UnionType>` fields in structs.

In `t_rs_generator::render_list_sync_read` (line 2016 of `t_rs_generator.cc`), when the list element type is a union, the generated code looks like this:

```rust
match UnionType::read_from_in_protocol(i_prot) {
    Ok(val) => { val.push(val); },
    ...
}
```

**Bugs:**

1. **Variable shadowing**: The match binding `val` shadows the outer list variable `val`. As a result, `val.push(val)` attempts to call `.push()` on the union element (which doesn't exist) instead of the `Vec`.

2. **Missing `Box::new()`**: The list type is `Vec<Box<UnionType>>`, but the element is not wrapped in `Box::new()` before pushing.

**Correct generated code should be:**

```rust
match UnionType::read_from_in_protocol(i_prot) {
    Ok(elem) => { val.push(Box::new(elem)); },
    ...
}
```

The same issue exists in `render_set_sync_read` (line 2051).

**Note:**  
The single-field deserialization path (`render_struct_sync_read`, line 1718) correctly handles boxing using `is_boxed ? "Box::new(val)" : "val"`, but the collection paths do not.

**Reproduction:**

Any `.thrift` file containing a struct with a `list<UnionType>` or `set<UnionType>` field.

**Example:**

```thrift
union MyUnion {
  1: i32 int_value
  2: string string_value
}

struct MyStruct {
  3: optional list<MyUnion> items
}
```)

> Rust codegen: `list<UnionType>` deserialization generates shadowed variable and missing Box wrapping
> ----------------------------------------------------------------------------------------------------
>
>                 Key: THRIFT-6058
>                 URL: https://issues.apache.org/jira/browse/THRIFT-6058
>             Project: Thrift
>          Issue Type: Bug
>            Reporter: Santiago Medina
>            Priority: Major
>




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