1use proc_macro2::TokenStream;
2use quote::quote;
3use syn::{Data, DeriveInput, Fields};
4
5use crate::helpers::{non_enum_error, HasStrumVariantProperties, HasTypeProperties};
6
7pub fn display_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
8 let name = &ast.ident;
9 let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
10 let variants = match &ast.data {
11 Data::Enum(v) => &v.variants,
12 _ => return Err(non_enum_error()),
13 };
14
15 let type_properties = ast.get_type_properties()?;
16
17 let mut arms = Vec::new();
18 for variant in variants {
19 let ident = &variant.ident;
20 let variant_properties = variant.get_variant_properties()?;
21
22 if variant_properties.disabled.is_some() {
23 continue;
24 }
25
26 // Look at all the serialize attributes.
27 let output = variant_properties.get_preferred_name(type_properties.case_style);
28
29 let params = match variant.fields {
30 Fields::Unit => quote! {},
31 Fields::Unnamed(..) => quote! { (..) },
32 Fields::Named(..) => quote! { {..} },
33 };
34
35 arms.push(quote! { #name::#ident #params => f.pad(#output) });
36 }
37
38 if arms.len() < variants.len() {
39 arms.push(quote! { _ => panic!("fmt() called on disabled variant.") });
40 }
41
42 Ok(quote! {
43 impl #impl_generics ::core::fmt::Display for #name #ty_generics #where_clause {
44 fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::result::Result<(), ::core::fmt::Error> {
45 match *self {
46 #(#arms),*
47 }
48 }
49 }
50 })
51}
52