fix: test stack overflow

* add `erg_proc_macros` crate

Cargo.toml

@@ -17,6 +17,7 @@ members = [
     "crates/erg_compiler",
     "crates/erg_parser",
     "crates/els",
+    "crates/erg_proc_macros/",
 ]
 
 [workspace.package]
@@ -68,6 +69,7 @@ erg_common = { version = "0.6.21-nightly.1", path = "./crates/erg_common" }
 erg_parser = { version = "0.6.21-nightly.1", path = "./crates/erg_parser" }
 erg_compiler = { version = "0.6.21-nightly.1", path = "./crates/erg_compiler" }
 els = { version = "0.1.33-nightly.1", path = "./crates/els" }
+erg_proc_macros = { version = "0.6.21-nightly.1", path = "./crates/erg_proc_macros" }
 
 [dependencies]
 erg_common = { workspace = true }

crates/els/Cargo.toml

@@ -23,11 +23,14 @@ experimental = ["erg_common/experimental", "erg_compiler/experimental"]
 [dependencies]
 erg_common = { workspace = true, features = ["els"] }
 erg_compiler = { workspace = true, features = ["els"] }
-molc = { version = "0.1.0" }
+molc = { version = "0.2" }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0.85"
 lsp-types = { version = "0.93.2", features = ["proposed"] }
 
+[dev-dependencies]
+erg_proc_macros = { workspace = true }
+
 [lib]
 path = "lib.rs"
 

crates/els/tests/test.rs

@@ -9,6 +9,7 @@ const FILE_B: &str = "tests/b.er";
 const FILE_IMPORTS: &str = "tests/imports.er";
 
 use els::{NormalizedUrl, Server};
+use erg_proc_macros::exec_new_thread;
 use molc::{add_char, oneline_range};
 
 #[test]
@@ -146,6 +147,7 @@ fn test_goto_definition() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 #[test]
+#[exec_new_thread]
 fn test_folding_range() -> Result<(), Box<dyn std::error::Error>> {
     let mut client = Server::bind_fake_client();
     client.request_initialize()?;

crates/erg_proc_macros/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "erg_proc_macros"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+edition.workspace = true
+repository.workspace = true
+homepage.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+erg_common = { workspace = true }
+syn = { version = "1.0", features = ["full"] }
+quote = "1.0"
+
+[lib]
+proc-macro = true

crates/erg_proc_macros/src/lib.rs

@@ -0,0 +1,56 @@
+use proc_macro::TokenStream;
+
+use quote::quote;
+use syn::{PathArguments, ReturnType, Type, TypePath};
+
+/// ```ignore
+/// #[exec_new_thread]
+/// fn foo() -> Result<isize, Box<dyn std::error::Error>> {
+///     ...
+/// }
+/// ```
+/// ↓ ↓
+/// ```ignore
+/// 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()
+}