sp_runtime_interface_proc_macro/pass_by/
inner.rs

1// This file is part of Substrate.
2
3// Copyright (C) Parity Technologies (UK) Ltd.
4// SPDX-License-Identifier: Apache-2.0
5
6// Licensed under the Apache License, Version 2.0 (the "License");
7// you may not use this file except in compliance with the License.
8// You may obtain a copy of the License at
9//
10// 	http://www.apache.org/licenses/LICENSE-2.0
11//
12// Unless required by applicable law or agreed to in writing, software
13// distributed under the License is distributed on an "AS IS" BASIS,
14// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15// See the License for the specific language governing permissions and
16// limitations under the License.
17
18//! Derive macro implementation of `PassBy` with the associated type set to `Inner` and of the
19//! helper trait `PassByInner`.
20//!
21//! It is required that the type is a newtype struct, otherwise an error is generated.
22
23use crate::utils::{generate_crate_access, generate_runtime_interface_include};
24
25use syn::{parse_quote, Data, DeriveInput, Error, Fields, Generics, Ident, Result, Type};
26
27use quote::quote;
28
29use proc_macro2::{Span, TokenStream};
30
31/// The derive implementation for `PassBy` with `Inner` and `PassByInner`.
32pub fn derive_impl(mut input: DeriveInput) -> Result<TokenStream> {
33	add_trait_bounds(&mut input.generics);
34	let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
35	let crate_include = generate_runtime_interface_include();
36	let crate_ = generate_crate_access();
37	let ident = input.ident;
38	let (inner_ty, inner_name) = extract_inner_ty_and_name(&input.data)?;
39
40	let access_inner = match inner_name {
41		Some(ref name) => quote!(self.#name),
42		None => quote!(self.0),
43	};
44
45	let from_inner = match inner_name {
46		Some(name) => quote!(Self { #name: inner }),
47		None => quote!(Self(inner)),
48	};
49
50	let res = quote! {
51		const _: () = {
52			#crate_include
53
54			impl #impl_generics #crate_::pass_by::PassBy for #ident #ty_generics #where_clause {
55				type PassBy = #crate_::pass_by::Inner<Self, #inner_ty>;
56			}
57
58			impl #impl_generics #crate_::pass_by::PassByInner for #ident #ty_generics #where_clause {
59				type Inner = #inner_ty;
60
61				fn into_inner(self) -> Self::Inner {
62					#access_inner
63				}
64
65				fn inner(&self) -> &Self::Inner {
66					&#access_inner
67				}
68
69				fn from_inner(inner: Self::Inner) -> Self {
70					#from_inner
71				}
72			}
73		};
74	};
75
76	Ok(res)
77}
78
79/// Add the `RIType` trait bound to every type parameter.
80fn add_trait_bounds(generics: &mut Generics) {
81	let crate_ = generate_crate_access();
82
83	generics
84		.type_params_mut()
85		.for_each(|type_param| type_param.bounds.push(parse_quote!(#crate_::RIType)));
86}
87
88/// Extract the inner type and optional name from given input data.
89///
90/// It also checks that the input data is a newtype struct.
91fn extract_inner_ty_and_name(data: &Data) -> Result<(Type, Option<Ident>)> {
92	if let Data::Struct(ref struct_data) = data {
93		match struct_data.fields {
94			Fields::Named(ref named) if named.named.len() == 1 => {
95				let field = &named.named[0];
96				return Ok((field.ty.clone(), field.ident.clone()))
97			},
98			Fields::Unnamed(ref unnamed) if unnamed.unnamed.len() == 1 => {
99				let field = &unnamed.unnamed[0];
100				return Ok((field.ty.clone(), field.ident.clone()))
101			},
102			_ => {},
103		}
104	}
105
106	Err(Error::new(
107		Span::call_site(),
108		"Only newtype/one field structs are supported by `PassByInner`!",
109	))
110}
sp_runtime_interface_proc_macro/pass_by/inner.rs

sp_runtime_interface_proc_macro/pass_by/
inner.rs
