sp_runtime_interface_proc_macro/pass_by/
enum_.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 `Enum`.
19//!
20//! Besides `PassBy`, `TryFrom<u8>` and `From<Self> for u8` are implemented for the type.
21
22use crate::utils::{generate_crate_access, generate_runtime_interface_include};
23
24use syn::{Data, DeriveInput, Error, Fields, Ident, Result};
25
26use quote::quote;
27
28use proc_macro2::{Span, TokenStream};
29
30/// The derive implementation for `PassBy` with `Enum`.
31pub fn derive_impl(input: DeriveInput) -> Result<TokenStream> {
32	let crate_include = generate_runtime_interface_include();
33	let crate_ = generate_crate_access();
34	let ident = input.ident;
35	let enum_fields = get_enum_field_idents(&input.data)?
36		.enumerate()
37		.map(|(i, v)| {
38			let i = i as u8;
39
40			v.map(|v| (quote!(#i => Ok(#ident::#v)), quote!(#ident::#v => #i)))
41		})
42		.collect::<Result<Vec<_>>>()?;
43	let try_from_variants = enum_fields.iter().map(|i| &i.0);
44	let into_variants = enum_fields.iter().map(|i| &i.1);
45
46	let res = quote! {
47		const _: () = {
48			#crate_include
49
50			impl #crate_::pass_by::PassBy for #ident {
51				type PassBy = #crate_::pass_by::Enum<#ident>;
52			}
53
54			impl TryFrom<u8> for #ident {
55				type Error = ();
56
57				fn try_from(inner: u8) -> core::result::Result<Self, ()> {
58					match inner {
59						#( #try_from_variants, )*
60						_ => Err(()),
61					}
62				}
63			}
64
65			impl From<#ident> for u8 {
66				fn from(var: #ident) -> u8 {
67					match var {
68						#( #into_variants ),*
69					}
70				}
71			}
72		};
73	};
74
75	Ok(res)
76}
77
78/// Get the enum fields idents of the given `data` object as iterator.
79///
80/// Returns an error if the number of variants is greater than `256`, the given `data` is not an
81/// enum or a variant is not an unit.
82fn get_enum_field_idents(data: &Data) -> Result<impl Iterator<Item = Result<&Ident>>> {
83	match data {
84		Data::Enum(d) =>
85			if d.variants.len() <= 256 {
86				Ok(d.variants.iter().map(|v| {
87					if let Fields::Unit = v.fields {
88						Ok(&v.ident)
89					} else {
90						Err(Error::new(
91							Span::call_site(),
92							"`PassByEnum` only supports unit variants.",
93						))
94					}
95				}))
96			} else {
97				Err(Error::new(Span::call_site(), "`PassByEnum` only supports `256` variants."))
98			},
99		_ => Err(Error::new(Span::call_site(), "`PassByEnum` only supports enums as input type.")),
100	}
101}
sp_runtime_interface_proc_macro/pass_by/enum_.rs

sp_runtime_interface_proc_macro/pass_by/
enum_.rs
