1use crate::utils::{AttrParams, DeriveType, State};
2use convert_case::{Case, Casing};
3use proc_macro2::TokenStream;
4use quote::{format_ident, quote};
5use syn::{DeriveInput, Fields, Result};
6
7pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
8 let state = State::with_attr_params(
9 input,
10 trait_name,
11 "is_variant".into(),
12 AttrParams {
13 enum_: vec!["ignore"],
14 variant: vec!["ignore"],
15 struct_: vec!["ignore"],
16 field: vec!["ignore"],
17 },
18 )?;
19 assert!(
20 state.derive_type == DeriveType::Enum,
21 "IsVariant can only be derived for enums",
22 );
23
24 let enum_name = &input.ident;
25 let (imp_generics, type_generics, where_clause) = input.generics.split_for_impl();
26
27 let mut funcs = vec![];
28 for variant_state in state.enabled_variant_data().variant_states {
29 let variant = variant_state.variant.unwrap();
30 let fn_name = format_ident!(
31 "is_{}",
32 variant.ident.to_string().to_case(Case::Snake),
33 span = variant.ident.span(),
34 );
35 let variant_ident = &variant.ident;
36
37 let data_pattern = match variant.fields {
38 Fields::Named(_) => quote! { {..} },
39 Fields::Unnamed(_) => quote! { (..) },
40 Fields::Unit => quote! {},
41 };
42 let func = quote! {
43 #[doc = "Returns `true` if this value is of type `"]
44 #[doc = stringify!(#variant_ident)]
45 #[doc = "`. Returns `false` otherwise"]
46 #[inline]
47 #[must_use]
48 pub const fn #fn_name(&self) -> bool {
49 derive_more::core::matches!(self, #enum_name ::#variant_ident #data_pattern)
50 }
51 };
52 funcs.push(func);
53 }
54
55 let imp = quote! {
56 #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
57 #[automatically_derived]
58 impl #imp_generics #enum_name #type_generics #where_clause {
59 #(#funcs)*
60 }
61 };
62
63 Ok(imp)
64}
65