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use proc_macro::TokenStream;
use quote::quote;
use syn::{Ident, LitStr, parse_macro_input};
enum EntryInput {
Typed { ident: Ident, strings: Vec<String> },
Untyped { strings: Vec<String> },
}
impl syn::parse::Parse for EntryInput {
fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
// entry!(EntryType, ["a", "b", "c"])
// entry!["a", "b", "c"] — comes in as just ["a", "b", "c"]
if input.peek(Ident) && input.peek2(syn::Token![,]) {
// entry!(EntryType, ["a", "b", "c"])
let ident: Ident = input.parse()?;
let _comma: syn::Token![,] = input.parse()?;
let content;
syn::bracketed!(content in input);
let strings = parse_strings(&content)?;
Ok(EntryInput::Typed { ident, strings })
} else {
// entry!["a", "b", "c"] — bare bracket content
let strings = parse_strings(input)?;
Ok(EntryInput::Untyped { strings })
}
}
}
fn parse_strings(input: &syn::parse::ParseBuffer) -> syn::Result<Vec<String>> {
let mut strings = Vec::new();
while !input.is_empty() {
let s: LitStr = input.parse()?;
strings.push(s.value());
if input.peek(syn::Token![,]) {
let _comma: syn::Token![,] = input.parse()?;
}
}
Ok(strings)
}
pub fn entry(input: TokenStream) -> TokenStream {
let parsed = parse_macro_input!(input as EntryInput);
let strings = match &parsed {
EntryInput::Typed { strings, .. } | EntryInput::Untyped { strings } => strings,
};
let string_exprs = strings
.iter()
.map(|s| {
let lit = syn::LitStr::new(s, proc_macro2::Span::call_site());
quote! { #lit.to_string() }
})
.collect::<Vec<_>>();
let expanded = match parsed {
EntryInput::Typed { ident, .. } => {
quote! {
#ident::new(vec![#(#string_exprs),*])
}
}
EntryInput::Untyped { .. } => {
quote! {
vec![#(#string_exprs),*].into()
}
}
};
expanded.into()
}
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