diff options
Diffstat (limited to 'mingling_macros/src/chain.rs')
| -rw-r--r-- | mingling_macros/src/chain.rs | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/mingling_macros/src/chain.rs b/mingling_macros/src/chain.rs index a91949d..e7b2db2 100644 --- a/mingling_macros/src/chain.rs +++ b/mingling_macros/src/chain.rs @@ -1,7 +1,9 @@ use proc_macro::TokenStream; use quote::{ToTokens, quote}; use syn::spanned::Spanned; -use syn::{FnArg, Ident, ItemFn, Pat, PatType, Signature, Type, TypePath, parse_macro_input}; +use syn::{ + FnArg, Ident, ItemFn, Pat, PatType, ReturnType, Signature, Type, TypePath, parse_macro_input, +}; /// Extracts the previous type and parameter name from function arguments fn extract_previous_info(sig: &Signature) -> syn::Result<(Pat, TypePath)> { @@ -67,6 +69,40 @@ pub fn chain_attr(attr: TokenStream, item: TokenStream) -> TokenStream { } } + // Check that return type is NextProcess + let return_type = &input_fn.sig.output; + match return_type { + ReturnType::Type(_, ty) => { + // Check if the return type is NextProcess + match &**ty { + Type::Path(type_path) => { + let last_segment = type_path.path.segments.last().unwrap(); + if last_segment.ident.to_string() != "NextProcess" { + return syn::Error::new( + ty.span(), + "Chain function must return `NextProcess`", + ) + .to_compile_error() + .into(); + } + } + _ => { + return syn::Error::new(ty.span(), "Chain function must return `NextProcess`") + .to_compile_error() + .into(); + } + } + } + ReturnType::Default => { + return syn::Error::new( + input_fn.sig.span(), + "Chain function must specify a return type (must be `NextProcess`)", + ) + .to_compile_error() + .into(); + } + } + // Extract the previous type and parameter name from function arguments let (prev_param, previous_type) = match extract_previous_info(&input_fn.sig) { Ok(info) => info, |