swc_config_macro/
merge.rs

1use proc_macro2::TokenStream;
2use quote::{quote, ToTokens};
3use swc_macros_common::{access_field, join_stmts};
4use syn::{parse_quote, DeriveInput, Expr, Field, Fields, Stmt, Token};
5
6pub fn expand(input: DeriveInput) -> TokenStream {
7    match &input.data {
8        syn::Data::Struct(s) => {
9            let body = call_merge_for_fields(&quote!(self), &s.fields);
10            let body = join_stmts(&body);
11
12            let ident = &input.ident;
13            parse_quote!(
14                #[automatically_derived]
15                impl swc_config::merge::Merge for #ident {
16                    fn merge(&mut self, _other: Self) {
17                        #body
18                    }
19                }
20            )
21        }
22        syn::Data::Enum(_) => unimplemented!("derive(Merge) does not support an enum"),
23        syn::Data::Union(_) => unimplemented!("derive(Merge) does not support a union"),
24    }
25}
26
27fn call_merge_for_fields(obj: &dyn ToTokens, fields: &Fields) -> Vec<Stmt> {
28    fn call_merge(obj: &dyn ToTokens, idx: usize, f: &Field) -> Expr {
29        let r = quote!(_other);
30
31        let l = access_field(obj, idx, f);
32        let r = access_field(&r, idx, f);
33        parse_quote!(swc_config::merge::Merge::merge(&mut #l, #r))
34    }
35
36    match fields {
37        Fields::Named(fs) => fs
38            .named
39            .iter()
40            .enumerate()
41            .map(|(idx, f)| call_merge(obj, idx, f))
42            .map(|expr| Stmt::Expr(expr, Some(Token![;](fs.brace_token.span.join()))))
43            .collect(),
44        Fields::Unnamed(fs) => fs
45            .unnamed
46            .iter()
47            .enumerate()
48            .map(|(idx, f)| call_merge(obj, idx, f))
49            .map(|expr| Stmt::Expr(expr, Some(Token![;](fs.paren_token.span.join()))))
50            .collect(),
51        Fields::Unit => unimplemented!("derive(Merge) does not support a unit struct"),
52    }
53}
swc_config_macro/merge.rs

swc_config_macro/
merge.rs
