1use crate::add_helpers::{struct_exprs, tuple_exprs};
2use crate::utils::{
3 add_extra_type_param_bound_op_output, field_idents, named_to_vec, numbered_vars,
4 unnamed_to_vec,
5};
6use proc_macro2::TokenStream;
7use quote::{format_ident, quote, ToTokens};
8use std::iter;
9use syn::{Data, DataEnum, DeriveInput, Field, Fields, Ident};
10
11pub fn expand(input: &DeriveInput, trait_name: &str) -> TokenStream {
12 let trait_name = trait_name.trim_end_matches("Self");
13 let trait_ident = format_ident!("{trait_name}");
14 let method_name = trait_name.to_lowercase();
15 let method_ident = format_ident!("{method_name}");
16 let input_type = &input.ident;
17
18 let generics = add_extra_type_param_bound_op_output(&input.generics, &trait_ident);
19 let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
20
21 let (output_type, block) = match input.data {
22 Data::Struct(ref data_struct) => match data_struct.fields {
23 Fields::Unnamed(ref fields) => (
24 quote! { #input_type #ty_generics },
25 tuple_content(input_type, &unnamed_to_vec(fields), &method_ident),
26 ),
27 Fields::Named(ref fields) => (
28 quote! { #input_type #ty_generics },
29 struct_content(input_type, &named_to_vec(fields), &method_ident),
30 ),
31 _ => panic!("Unit structs cannot use derive({trait_name})"),
32 },
33 Data::Enum(ref data_enum) => (
34 quote! {
35 derive_more::core::result::Result<#input_type #ty_generics, derive_more::BinaryError>
36 },
37 enum_content(input_type, data_enum, &method_ident),
38 ),
39
40 _ => panic!("Only structs and enums can use derive({trait_name})"),
41 };
42
43 quote! {
44 #[automatically_derived]
45 impl #impl_generics derive_more::core::ops::#trait_ident
46 for #input_type #ty_generics #where_clause {
47 type Output = #output_type;
48
49 #[inline]
50 #[track_caller]
51 fn #method_ident(self, rhs: #input_type #ty_generics) -> #output_type {
52 #block
53 }
54 }
55 }
56}
57
58fn tuple_content<T: ToTokens>(
59 input_type: &T,
60 fields: &[&Field],
61 method_ident: &Ident,
62) -> TokenStream {
63 let exprs: Vec = tuple_exprs(fields, method_ident);
64 quote! { #input_type(#(#exprs),*) }
65}
66
67fn struct_content(
68 input_type: &Ident,
69 fields: &[&Field],
70 method_ident: &Ident,
71) -> TokenStream {
72 // It's safe to unwrap because struct fields always have an identifier
73 let exprs: Vec = struct_exprs(fields, method_ident);
74 let field_names: Vec<&Ident> = field_idents(fields);
75
76 quote! { #input_type{#(#field_names: #exprs),*} }
77}
78
79#[allow(clippy::cognitive_complexity)]
80fn enum_content(
81 input_type: &Ident,
82 data_enum: &DataEnum,
83 method_ident: &Ident,
84) -> TokenStream {
85 let mut matches = vec![];
86 let mut method_iter = iter::repeat(method_ident);
87
88 for variant in &data_enum.variants {
89 let subtype = &variant.ident;
90 let subtype = quote! { #input_type::#subtype };
91
92 match variant.fields {
93 Fields::Unnamed(ref fields) => {
94 // The pattern that is outputted should look like this:
95 // (Subtype(left_vars), TypePath(right_vars)) => Ok(TypePath(exprs))
96 let size = unnamed_to_vec(fields).len();
97 let l_vars = &numbered_vars(size, "l_");
98 let r_vars = &numbered_vars(size, "r_");
99 let method_iter = method_iter.by_ref();
100 let matcher = quote! {
101 (#subtype(#(#l_vars),*),
102 #subtype(#(#r_vars),*)) => {
103 derive_more::core::result::Result::Ok(
104 #subtype(#(#l_vars.#method_iter(#r_vars)),*)
105 )
106 }
107 };
108 matches.push(matcher);
109 }
110 Fields::Named(ref fields) => {
111 // The pattern that is outputted should look like this:
112 // (Subtype{a: __l_a, ...}, Subtype{a: __r_a, ...} => {
113 // Ok(Subtype{a: __l_a.add(__r_a), ...})
114 // }
115 let field_vec = named_to_vec(fields);
116 let size = field_vec.len();
117 let field_names = &field_idents(&field_vec);
118 let l_vars = &numbered_vars(size, "l_");
119 let r_vars = &numbered_vars(size, "r_");
120 let method_iter = method_iter.by_ref();
121 let matcher = quote! {
122 (#subtype{#(#field_names: #l_vars),*},
123 #subtype{#(#field_names: #r_vars),*}) => {
124 derive_more::core::result::Result::Ok(#subtype{
125 #(#field_names: #l_vars.#method_iter(#r_vars)),*
126 })
127 }
128 };
129 matches.push(matcher);
130 }
131 Fields::Unit => {
132 let operation_name = method_ident.to_string();
133 matches.push(quote! {
134 (#subtype, #subtype) => derive_more::core::result::Result::Err(
135 derive_more::BinaryError::Unit(
136 derive_more::UnitError::new(#operation_name)
137 )
138 )
139 });
140 }
141 }
142 }
143
144 if data_enum.variants.len() > 1 {
145 // In the strange case where there's only one enum variant this is would be an unreachable
146 // match.
147 let operation_name = method_ident.to_string();
148 matches.push(quote! {
149 _ => derive_more::core::result::Result::Err(derive_more::BinaryError::Mismatch(
150 derive_more::WrongVariantError::new(#operation_name)
151 ))
152 });
153 }
154 quote! {
155 match (self, rhs) {
156 #(#matches),*
157 }
158 }
159}
160