39 lines
1.4 KiB
Rust
39 lines
1.4 KiB
Rust
// Copyright (C) Parity Technologies (UK) Ltd.
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// This file is part of Pezkuwi.
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// Pezkuwi is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Pezkuwi is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Pezkuwi. If not, see <http://www.gnu.org/licenses/>.
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//! Simple derive macro for getting the number of variants in an enum.
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use proc_macro2::TokenStream as TokenStream2;
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use quote::{format_ident, quote};
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use syn::{Data, DeriveInput, Error, Result};
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pub fn derive(input: DeriveInput) -> Result<TokenStream2> {
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let data_enum = match &input.data {
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Data::Enum(data_enum) => data_enum,
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_ => return Err(Error::new_spanned(&input, "Expected an enum.")),
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};
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let ident = format_ident!("{}NumVariants", input.ident);
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let number_of_variants: usize = data_enum.variants.iter().count();
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Ok(quote! {
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pub struct #ident;
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impl ::frame_support::traits::Get<u32> for #ident {
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fn get() -> u32 {
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#number_of_variants as u32
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}
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}
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})
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}
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