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

// This file is part of Substrate.

// Copyright (C) 2021 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use syn::spanned::Spanned;

/// Derive Clone but do not bound any generic.
pub fn derive_default_no_bound(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
	let input: syn::DeriveInput = match syn::parse(input) {
		Ok(input) => input,
		Err(e) => return e.to_compile_error().into(),
	};

	let name = &input.ident;
	let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();

	let impl_ = match input.data {
		syn::Data::Struct(struct_) => match struct_.fields {
			syn::Fields::Named(named) => {
				let fields = named.named.iter().map(|i| &i.ident).map(|i| {
					quote::quote_spanned!(i.span() =>
						#i: core::default::Default::default()
					)
				});

				quote::quote!( Self { #( #fields, )* } )
			},
			syn::Fields::Unnamed(unnamed) => {
				let fields =
					unnamed.unnamed.iter().enumerate().map(|(i, _)| syn::Index::from(i)).map(|i| {
						quote::quote_spanned!(i.span() =>
							core::default::Default::default()
						)
					});

				quote::quote!( Self ( #( #fields, )* ) )
			},
			syn::Fields::Unit => {
				quote::quote!(Self)
			},
		},
		syn::Data::Enum(enum_) =>
			if let Some(first_variant) = enum_.variants.first() {
				let variant_ident = &first_variant.ident;
				match &first_variant.fields {
					syn::Fields::Named(named) => {
						let fields = named.named.iter().map(|i| &i.ident).map(|i| {
							quote::quote_spanned!(i.span() =>
								#i: core::default::Default::default()
							)
						});

						quote::quote!( #name :: #ty_generics :: #variant_ident { #( #fields, )* } )
					},
					syn::Fields::Unnamed(unnamed) => {
						let fields = unnamed
							.unnamed
							.iter()
							.enumerate()
							.map(|(i, _)| syn::Index::from(i))
							.map(|i| {
								quote::quote_spanned!(i.span() =>
									core::default::Default::default()
								)
							});

						quote::quote!( #name :: #ty_generics :: #variant_ident ( #( #fields, )* ) )
					},
					syn::Fields::Unit => quote::quote!( #name :: #ty_generics :: #variant_ident ),
				}
			} else {
				quote::quote!(Self)
			},
		syn::Data::Union(_) => {
			let msg = "Union type not supported by `derive(CloneNoBound)`";
			return syn::Error::new(input.span(), msg).to_compile_error().into()
		},
	};

	quote::quote!(
		const _: () = {
			impl #impl_generics core::default::Default for #name #ty_generics #where_clause {
				fn default() -> Self {
					#impl_
				}
			}
		};
	)
	.into()
}