fix: test stack overflow

* add `erg_proc_macros` crate

crates/erg_proc_macros/src/lib.rs

@@ -0,0 +1,56 @@
+use proc_macro::TokenStream;
+
+use quote::quote;
+use syn::{PathArguments, ReturnType, Type, TypePath};
+
+/// ```rust_
+/// #[exec_new_thread]
+/// fn foo() -> Result<isize, Box<dyn std::error::Error>> {
+///     ...
+/// }
+/// ```
+/// ↓ ↓
+/// ```rust_
+/// fn foo() -> Result<isize, Box<dyn std::error::Error>> {
+///   fn error(msg: impl Into<String>) -> std::io::Error {
+///     std::io::Error::new(std::io::ErrorKind::Other, msg.into())
+///   }
+///   fn f() -> Result<(), Box<dyn std::error::Error + Send>> {
+///     {...}.map_err(|e| Box::new(error(e.to_string())) as _)
+///   }
+///   exec_new_thread(f, "foo").map_err(|e| e as _)
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn exec_new_thread(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    let mut item_fn = syn::parse_macro_input!(item as syn::ItemFn);
+    let name = item_fn.sig.ident.to_string();
+    let ReturnType::Type(_, out) = &item_fn.sig.output else {
+        todo!()
+    };
+    let Type::Path(TypePath { path, .. }) = out.as_ref() else {
+        todo!()
+    };
+    let result_t = path.segments.first().unwrap();
+    let PathArguments::AngleBracketed(args) = &result_t.arguments else {
+        todo!()
+    };
+    let t = args.args.first().unwrap();
+    let name = syn::LitStr::new(&name, item_fn.sig.ident.span());
+    let block = item_fn.block;
+    let block = syn::parse_quote! {{
+        fn error(msg: impl Into<String>) -> std::io::Error {
+            std::io::Error::new(std::io::ErrorKind::Other, msg.into())
+        }
+        fn _f() -> Result<#t, Box<dyn std::error::Error>> {
+            #block
+        }
+        fn f() -> Result<#t, Box<dyn std::error::Error + Send>> {
+            _f().map_err(|e| Box::new(error(e.to_string())) as _)
+        }
+        erg_common::spawn::exec_new_thread(f, #name).map_err(|e| e as _)
+    }};
+    item_fn.block = Box::new(block);
+    let item = quote! { #item_fn };
+    item.into()
+}