1//! [`Debug`](trait@std::fmt::Debug) implementation.
2
3use proc_macro2::TokenStream;
4use quote::quote;
5
6use crate::{Data, DeriveTrait, Item, SimpleType, SplitGenerics, TraitImpl};
7
8/// Dummy-struct implement [`Trait`](crate::Trait) for
9/// [`Debug`](trait@std::fmt::Debug).
10pub struct Debug;
11
12impl TraitImpl for Debug {
13 fn as_str(&self) -> &'static str {
14 "Debug"
15 }
16
17 fn default_derive_trait(&self) -> DeriveTrait {
18 DeriveTrait::Debug
19 }
20
21 fn build_signature(
22 &self,
23 _any_bound: bool,
24 _item: &Item,
25 _generics: &SplitGenerics<'_>,
26 _traits: &[DeriveTrait],
27 _trait_: &DeriveTrait,
28 body: &TokenStream,
29 ) -> TokenStream {
30 quote! {
31 fn fmt(&self, __f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
32 match self {
33 #body
34 }
35 }
36 }
37 }
38
39 fn build_body(
40 &self,
41 _any_bound: bool,
42 _traits: &[DeriveTrait],
43 trait_: &DeriveTrait,
44 data: &Data,
45 ) -> TokenStream {
46 let self_pattern = &data.self_pattern();
47 let debug_name = data.ident.to_string();
48
49 match data.simple_type() {
50 SimpleType::Struct(_) => {
51 let self_ident = data.iter_self_ident(**trait_);
52 let debug_fields = data
53 .iter_field_ident(**trait_)
54 .map(|field| field.to_string());
55
56 let finish = if data.any_skip_trait(**trait_) {
57 quote! { finish_non_exhaustive }
58 } else {
59 quote! { finish }
60 };
61
62 quote! {
63 #self_pattern => {
64 let mut __builder = ::core::fmt::Formatter::debug_struct(__f, #debug_name);
65 #(::core::fmt::DebugStruct::field(&mut __builder, #debug_fields, #self_ident);)*
66 ::core::fmt::DebugStruct::#finish(&mut __builder)
67 }
68 }
69 }
70 SimpleType::Tuple(_) => {
71 let self_ident = data.iter_self_ident(**trait_);
72
73 quote! {
74 #self_pattern => {
75 let mut __builder = ::core::fmt::Formatter::debug_tuple(__f, #debug_name);
76 #(::core::fmt::DebugTuple::field(&mut __builder, #self_ident);)*
77 ::core::fmt::DebugTuple::finish(&mut __builder)
78 }
79 }
80 }
81 SimpleType::Unit(_) => {
82 quote! { #self_pattern => ::core::fmt::Formatter::write_str(__f, #debug_name), }
83 }
84 SimpleType::Union(_) => unreachable!("unexpected trait for union"),
85 }
86 }
87}
88