derive_more_impl/
unwrap.rs

1use crate::utils::{AttrParams, DeriveType, State};
2use convert_case::{Case, Casing};
3use proc_macro2::TokenStream;
4use quote::{format_ident, quote};
5use syn::{DeriveInput, Fields, Ident, Result, Type};
6
7pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
8    let state = State::with_attr_params(
9        input,
10        trait_name,
11        "unwrap".into(),
12        AttrParams {
13            enum_: vec!["ignore", "owned", "ref", "ref_mut"],
14            variant: vec!["ignore", "owned", "ref", "ref_mut"],
15            struct_: vec!["ignore"],
16            field: vec!["ignore"],
17        },
18    )?;
19    assert!(
20        state.derive_type == DeriveType::Enum,
21        "Unwrap can only be derived for enums",
22    );
23
24    let enum_name = &input.ident;
25    let (imp_generics, type_generics, where_clause) = input.generics.split_for_impl();
26
27    let variant_data = state.enabled_variant_data();
28
29    let mut funcs = vec![];
30    for (variant_state, info) in
31        Iterator::zip(variant_data.variant_states.iter(), variant_data.infos)
32    {
33        let variant = variant_state.variant.unwrap();
34        let fn_name = format_ident!(
35            "unwrap_{ident}",
36            ident = variant.ident.to_string().to_case(Case::Snake),
37            span = variant.ident.span(),
38        );
39        let ref_fn_name = format_ident!(
40            "unwrap_{ident}_ref",
41            ident = variant.ident.to_string().to_case(Case::Snake),
42            span = variant.ident.span(),
43        );
44        let mut_fn_name = format_ident!(
45            "unwrap_{ident}_mut",
46            ident = variant.ident.to_string().to_case(Case::Snake),
47            span = variant.ident.span(),
48        );
49        let variant_ident = &variant.ident;
50        let (data_pattern, ret_value, data_types) = get_field_info(&variant.fields);
51        let pattern = quote! { #enum_name :: #variant_ident #data_pattern };
52
53        let (failed_block, failed_block_ref, failed_block_mut) = (
54            failed_block(&state, enum_name, &fn_name),
55            failed_block(&state, enum_name, &ref_fn_name),
56            failed_block(&state, enum_name, &mut_fn_name),
57        );
58
59        let doc_owned = format!(
60            "Unwraps this value to the `{enum_name}::{variant_ident}` variant.\n",
61        );
62        let doc_ref = format!(
63            "Unwraps this reference to the `{enum_name}::{variant_ident}` variant.\n",
64        );
65        let doc_mut = format!(
66            "Unwraps this mutable reference to the `{enum_name}::{variant_ident}` variant.\n",
67        );
68        let doc_else = "Panics if this value is of any other type.";
69
70        let func = quote! {
71            #[inline]
72            #[track_caller]
73            #[doc = #doc_owned]
74            #[doc = #doc_else]
75            pub fn #fn_name(self) -> (#(#data_types),*) {
76                match self {
77                    #pattern => #ret_value,
78                    val @ _ => #failed_block,
79                }
80            }
81        };
82
83        let ref_func = quote! {
84            #[inline]
85            #[track_caller]
86            #[doc = #doc_ref]
87            #[doc = #doc_else]
88            pub fn #ref_fn_name(&self) -> (#(&#data_types),*) {
89                match self {
90                    #pattern => #ret_value,
91                    val @ _ => #failed_block_ref,
92                }
93            }
94        };
95
96        let mut_func = quote! {
97            #[inline]
98            #[track_caller]
99            #[doc = #doc_mut]
100            #[doc = #doc_else]
101            pub fn #mut_fn_name(&mut self) -> (#(&mut #data_types),*) {
102                match self {
103                    #pattern => #ret_value,
104                    val @ _ => #failed_block_mut,
105                }
106            }
107        };
108
109        if info.owned && state.default_info.owned {
110            funcs.push(func);
111        }
112        if info.ref_ && state.default_info.ref_ {
113            funcs.push(ref_func);
114        }
115        if info.ref_mut && state.default_info.ref_mut {
116            funcs.push(mut_func);
117        }
118    }
119
120    let imp = quote! {
121        #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
122        #[automatically_derived]
123        impl #imp_generics #enum_name #type_generics #where_clause {
124            #(#funcs)*
125        }
126    };
127
128    Ok(imp)
129}
130
131fn get_field_info(fields: &Fields) -> (TokenStream, TokenStream, Vec<&Type>) {
132    match fields {
133        Fields::Named(_) => panic!("cannot unwrap anonymous records"),
134        Fields::Unnamed(ref fields) => {
135            let (idents, types) = fields
136                .unnamed
137                .iter()
138                .enumerate()
139                .map(|(n, it)| (format_ident!("field_{n}"), &it.ty))
140                .unzip::<_, _, Vec<_>, Vec<_>>();
141            (quote! { (#(#idents),*) }, quote! { (#(#idents),*) }, types)
142        }
143        Fields::Unit => (quote! {}, quote! { () }, vec![]),
144    }
145}
146
147fn failed_block(state: &State, enum_name: &Ident, fn_name: &Ident) -> TokenStream {
148    let arms = state
149        .variant_states
150        .iter()
151        .map(|it| it.variant.unwrap())
152        .map(|variant| {
153            let data_pattern = match variant.fields {
154                Fields::Named(_) => quote! { {..} },
155                Fields::Unnamed(_) => quote! { (..) },
156                Fields::Unit => quote! {},
157            };
158            let variant_ident = &variant.ident;
159            let panic_msg = format!(
160                "called `{enum_name}::{fn_name}()` on a `{enum_name}::{variant_ident}` value"
161            );
162            quote! { #enum_name :: #variant_ident #data_pattern => panic!(#panic_msg) }
163        });
164
165    quote! {
166        match val {
167            #(#arms),*
168        }
169    }
170}
derive_more_impl/unwrap.rs

derive_more_impl/
unwrap.rs
