dede 0.1.1

macro: derive Deref and DerefMut
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167

//! # dede
//! DErive DEref
//! 
//! there were already some macros for deriving `Deref`
//! but wasn't flexible enough
//! 
//! this macro supports structs with generic types and tuple structs
//! 
//! ```rust
//! use dede::*;
//! 
//! #[derive(Deref, DerefMut)]
//! pub struct Foo {
//! 	#[deref]
//! 	bar: usize
//! }
//! ```



use quote::{ToTokens, quote};
use syn::{Data, DeriveInput, Fields, ImplItem, Meta, Token, punctuated::Punctuated, Type};
use proc_macro2::TokenStream as TokenStream2;

#[proc_macro_derive(Deref, attributes(deref))]
pub fn derive_deref(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
	let input = syn::parse::<DeriveInput>(item).expect("`Deref` macro can only be used for struct");
	if let Data::Struct(data_struct) = input.data {
		let mut field_option: Option<(TokenStream2, &Type)> = None;
		match &data_struct.fields {
			Fields::Named(fields_named) => {
				'a: for field in fields_named.named.iter() {
					for attr in field.attrs.iter() {
						if let Meta::Path(path) =  attr.parse_meta().unwrap() {
							let last = path.segments.last().unwrap();
							let ident = &last.ident;
							if ident.to_string() == "deref" {
								field_option = Some((field.ident.as_ref().unwrap().to_token_stream(), &field.ty));
								break 'a;
							}
						}
					}
				}
			},
			Fields::Unnamed(fields_unnamed) => {
				let mut i = 0;
				'b: for field in fields_unnamed.unnamed.iter() {
					for attr in field.attrs.iter() {
						if let Meta::Path(path) =  attr.parse_meta().unwrap() {
							let last = path.segments.last().unwrap();
							let ident = &last.ident;
							if ident.to_string() == "deref" {
								field_option = Some((syn::Index::from(i).to_token_stream(), &field.ty));
								break 'b;
							}
						}
					}
					i += 1;
				}
			},
			Fields::Unit => {}
		};
		if let Some((field_token, field_type)) = field_option {
			let mut type_args: Punctuated<_, syn::token::Comma> = Punctuated::new();
			for param in input.generics.type_params() {
				type_args.push(param.ident.clone());
			}

			let items = quote! {
				type Target = #field_type;

				fn deref(&self) -> &Self::Target {
					&self.#field_token
				}
			};

			let span = proc_macro2::Span::call_site();
			let ident = &input.ident;
			syn::ItemImpl {
				attrs: vec![],
				defaultness: None,
				unsafety: None,
				impl_token: Token![impl](span),
				generics: input.generics.clone(),
				trait_: Some((None, syn::parse2(quote! { std::ops::Deref }).unwrap(), Token![for](span))),
				self_ty: Box::new(syn::parse2(quote! { #ident<#type_args> }).unwrap()),
				brace_token: syn::token::Brace { span },
				items: vec![ImplItem::Verbatim(items)] 
			}.to_token_stream().into()
		} else {
			proc_macro::TokenStream::new()
		}
	} else {
		proc_macro::TokenStream::new()
	}
}

#[proc_macro_derive(DerefMut, attributes(deref))]
pub fn derive_deref_mut(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
	let input = syn::parse::<DeriveInput>(item).expect("`DerefMut` macro can only be used for struct");
	if let Data::Struct(data_struct) = input.data {
		let mut field_option: Option<(TokenStream2, &Type)> = None;
		match &data_struct.fields {
			Fields::Named(fields_named) => {
				'a: for field in fields_named.named.iter() {
					for attr in field.attrs.iter() {
						if let Meta::Path(path) =  attr.parse_meta().unwrap() {
							let last = path.segments.last().unwrap();
							let ident = &last.ident;
							if ident.to_string() == "deref" {
								field_option = Some((field.ident.as_ref().unwrap().to_token_stream(), &field.ty));
								break 'a;
							}
						}
					}
				}
			},
			Fields::Unnamed(fields_unnamed) => {
				let mut i = 0;
				'b: for field in fields_unnamed.unnamed.iter() {
					for attr in field.attrs.iter() {
						if let Meta::Path(path) =  attr.parse_meta().unwrap() {
							let last = path.segments.last().unwrap();
							let ident = &last.ident;
							if ident.to_string() == "deref" {
								field_option = Some((syn::Index::from(i).to_token_stream(), &field.ty));
								break 'b;
							}
						}
					}
					i += 1;
				}
			},
			Fields::Unit => {}
		};
		if let Some((field_token, _field_type)) = field_option {
			let mut type_args: Punctuated<_, syn::token::Comma> = Punctuated::new();
			for param in input.generics.type_params() {
				type_args.push(param.ident.clone());
			}

			let items = quote! {
				fn deref_mut(&mut self) -> &mut Self::Target {
					&mut self.#field_token
				}
			};

			let span = proc_macro2::Span::call_site();
			let ident = &input.ident;
			syn::ItemImpl {
				attrs: vec![],
				defaultness: None,
				unsafety: None,
				impl_token: Token![impl](span),
				generics: input.generics.clone(),
				trait_: Some((None, syn::parse2(quote! { std::ops::DerefMut }).unwrap(), Token![for](span))),
				self_ty: Box::new(syn::parse2(quote! { #ident<#type_args> }).unwrap()),
				brace_token: syn::token::Brace { span },
				items: vec![ImplItem::Verbatim(items)] 
			}.to_token_stream().into()
		} else {
			proc_macro::TokenStream::new()
		}
	} else {
		proc_macro::TokenStream::new()
	}
}