Auto merge of #6402 - pietroalbini:fix-cargofix, r=alexcrichton

Only ensure solutions are in the same file in cargo fix

This PR changes `cargo fix` to avoid rejecting machine-applicable lints with multiple suggestions. Instead, now it only checks the solutions are in the same file.

I don't know how to write a test for this, since no lint in rustc relies on the new behavior and the existing `cargo fix` tests just invoke lints in rustc. Any idea on that would be appreciated.

r? @alexcrichton
cc @killercup
fixes #6401

src/cargo/ops/fix.rs

@@ -400,21 +400,21 @@ fn rustfix_and_fix(
     for suggestion in suggestions {
         trace!("suggestion");
         // Make sure we've got a file associated with this suggestion and all
-        // snippets point to the same location. Right now it's not clear what
-        // we would do with multiple locations.
-        let (file_name, range) = match suggestion.snippets.get(0) {
-            Some(s) => (s.file_name.clone(), s.line_range),
-            None => {
-                trace!("rejecting as it has no snippets {:?}", suggestion);
-                continue;
-            }
+        // snippets point to the same file. Right now it's not clear what
+        // we would do with multiple files.
+        let file_names = suggestion.solutions.iter()
+            .flat_map(|s| s.replacements.iter())
+            .map(|r| &r.snippet.file_name);
+
+        let file_name = if let Some(file_name) = file_names.clone().next() {
+            file_name.clone()
+        } else {
+            trace!("rejecting as it has no solutions {:?}", suggestion);
+            continue;
         };
-        if !suggestion
-            .snippets
-            .iter()
-            .all(|s| s.file_name == file_name && s.line_range == range)
-        {
-            trace!("rejecting as it spans multiple files {:?}", suggestion);
+
+        if !file_names.clone().all(|f| f == &file_name) {
+            trace!("rejecting as it changes multiple files: {:?}", suggestion);
             continue;
         }