Report a better error than a panic in case there are suggestions for other files than the main file

Author: oli-obk

CHANGELOG.md

@@ -16,6 +16,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* report an error instead of panicking when encountering a suggestion that does not belong to the main file.
+
 ### Changed
 
 * crate-private span handling was passed off to the `spanned` crate, improving some diagnostics along the way.

src/lib.rs

@@ -874,6 +874,14 @@ fn run_rustfix(
             if suggestions.is_empty() {
                 None
             } else {
+                let path_str = path.display().to_string();
+                for sugg in &suggestions {
+                    for snip in &sugg.snippets {
+                        if snip.file_name != path_str {
+                            return Some(Err(anyhow::anyhow!("cannot apply suggestions for `{}` since main file is `{path_str}`. Please use `//@no-rustfix` to disable rustfix", snip.file_name)));
+                        }
+                    }
+                }
                 Some(rustfix::apply_suggestions(
                     &std::fs::read_to_string(path).unwrap(),
                     &suggestions,