derive_more_impl/
deref_mut.rs

1use crate::utils::{add_extra_where_clauses, SingleFieldData, State};
2use proc_macro2::TokenStream;
3use quote::quote;
4use syn::{parse::Result, DeriveInput};
5
6/// Provides the hook to expand `#[derive(DerefMut)]` into an implementation of `DerefMut`
7pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
8    let state =
9        State::with_field_ignore_and_forward(input, trait_name, "deref_mut".into())?;
10    let SingleFieldData {
11        input_type,
12        trait_path,
13        casted_trait,
14        ty_generics,
15        field_type,
16        member,
17        info,
18        ..
19    } = state.assert_single_enabled_field();
20    let (body, generics) = if info.forward {
21        (
22            quote! { #casted_trait::deref_mut(&mut #member) },
23            add_extra_where_clauses(
24                &input.generics,
25                quote! {
26                    where #field_type: #trait_path
27                },
28            ),
29        )
30    } else {
31        (quote! { &mut #member }, input.generics.clone())
32    };
33    let (impl_generics, _, where_clause) = generics.split_for_impl();
34
35    Ok(quote! {
36        #[automatically_derived]
37        impl #impl_generics #trait_path for #input_type #ty_generics #where_clause {
38            #[inline]
39            fn deref_mut(&mut self) -> &mut Self::Target {
40                #body
41            }
42        }
43    })
44}
derive_more_impl/deref_mut.rs

derive_more_impl/
deref_mut.rs
