fix: Prefer exact prefix/suffix matches when trimming replacements

Author: Muscraft

src/renderer/source_map.rs

@@ -779,18 +779,24 @@ pub(crate) fn as_substr<'a>(
     original: &'a str,
     suggestion: &'a str,
 ) -> Option<(usize, &'a str, usize)> {
-    let common_prefix = original
-        .chars()
-        .zip(suggestion.chars())
-        .take_while(|(c1, c2)| c1 == c2)
-        .map(|(c, _)| c.len_utf8())
-        .sum();
-    let original = &original[common_prefix..];
-    let suggestion = &suggestion[common_prefix..];
-    if let Some(stripped) = suggestion.strip_suffix(original) {
-        let common_suffix = original.len();
-        Some((common_prefix, stripped, common_suffix))
+    if let Some(stripped) = suggestion.strip_prefix(original) {
+        Some((original.len(), stripped, 0))
+    } else if let Some(stripped) = suggestion.strip_suffix(original) {
+        Some((0, stripped, original.len()))
     } else {
-        None
+        let common_prefix = original
+            .chars()
+            .zip(suggestion.chars())
+            .take_while(|(c1, c2)| c1 == c2)
+            .map(|(c, _)| c.len_utf8())
+            .sum();
+        let original = &original[common_prefix..];
+        let suggestion = &suggestion[common_prefix..];
+        if let Some(stripped) = suggestion.strip_suffix(original) {
+            let common_suffix = original.len();
+            Some((common_prefix, stripped, common_suffix))
+        } else {
+            None
+        }
     }
 }

tests/formatter.rs

@@ -5045,7 +5045,7 @@ fn original_matches_replacement_suffix() {
 help: consider importing this module instead
   |
 1 | use std::sync;
-  |      +++++
+  |     +++++
 "#]];
     let renderer = Renderer::plain();
     assert_data_eq!(renderer.render(input), expected_ascii);
@@ -5059,7 +5059,7 @@ help: consider importing this module instead
 help: consider importing this module instead
   ╭╴
 1 │ use std::sync;
-  ╰╴     +++++
+  ╰╴    +++++
 "#]];
     let renderer = renderer.decor_style(DecorStyle::Unicode);
     assert_data_eq!(renderer.render(input), expected_unicode);