Function macro_tools::phantom::add_to_item

pub fn add_to_item(input: &ItemStruct) -> ItemStruct

Adds a PhantomData field to a struct to manage generic parameter usage.

This function clones a given syn::ItemStruct, calculates the appropriate PhantomData usage based on the struct’s generic parameters, and adds a corresponding PhantomData field. This field helps in handling ownership and lifetime indications for generic parameters, ensuring that they are correctly accounted for in type checking, even if they are not directly used in the struct’s fields.

Parameters

• input: A reference to the syn::ItemStruct which describes the structure to which the PhantomData field will be added.

Returns

Returns a new syn::ItemStruct with the PhantomData field added to its list of fields.

Examples

use syn::{ parse_quote, ItemStruct };

let input_struct : ItemStruct = parse_quote!
{
  pub struct MyStruct< T, U >
  {
    data : T,
  }
};

let modified_struct = macro_tools::phantom::add_to_item( &input_struct );
println!( "{:#?}", modified_struct );

// Output will include a _phantom field of type `PhantomData< ( T, U ) >`