derive_more_impl/
is_variant.rs

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}
derive_more_impl/is_variant.rs

derive_more_impl/
is_variant.rs
