[fearless_simd_gen]: Fix rustfmt style_edition defaulting to 2015 (#13)

Generated code is formatted with rustfmt. However, by default rustfmt uses the 2015 edition. This PR adds rustfmt.toml such that generating the code and cargo fmt match.

Author: ajakubowicz-canva

fearless_simd_gen/src/main.rs

@@ -56,9 +56,9 @@ impl Module {
         }
     }
 
-    fn generate_string(self) -> String {
+    fn generate_string(self, name: &str) -> String {
         let code = self.generate_code();
-        let parsed = syn::parse_file(&code.to_string()).expect("error parsing {name}");
+        let parsed = syn::parse_file(&code.to_string()).expect(&format!("error parsing {name}"));
         let code_str = prettyplease::unparse(&parsed);
         format!("// This file is autogenerated by fearless_simd_gen\n\n{code_str}")
     }
@@ -101,7 +101,7 @@ fn main() {
             let name = module.file_base();
             let path = base_dir.join(format!("{name}.rs"));
             let file = File::create(&path).expect("error creating {path:?}");
-            let code_str = module.generate_string();
+            let code_str = module.generate_string(name);
             write_formatted(code_str.as_bytes(), file);
         }
     }

rustfmt.toml

@@ -0,0 +1 @@
+edition = "2024"