Handle non-ascii character at boundary

src/string.rs

@@ -282,7 +282,7 @@ fn break_string(max_width: usize, trim_end: bool, line_end: &str, input: &[&str]
     // Find the position in input for breaking the string
     if line_end.is_empty()
         && trim_end
-        && !is_whitespace(input[max_width_index_in_input - 1])
+        && !is_whitespace(input[max_width_index_in_input.checked_sub(1).unwrap_or(0)])
         && is_whitespace(input[max_width_index_in_input])
     {
         // At a breaking point already

tests/target/issue-5023.rs

@@ -0,0 +1,19 @@
+// rustfmt-wrap_comments: true
+fn main() {
+    if xxx {
+        let xxx = xxx
+            .into_iter()
+            .filter(|(xxx, xxx)| {
+                if let Some(x) = Some(1) {
+                    // xxxxxxxxxxxxxxxxxx, xxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxxx xxx xxxxxxx, xxxxx xxx
+                    // xxxxxxxxxx. xxxxxxxxxxxxxxxx，xxxxxxxxxxxxxxxxx xxx xxxxxxx
+                    // 是sdfadsdfxxxxxxxxx，sdfaxxxxxx_xxxxx_masdfaonxxx，
+                    if false {
+                        return true;
+                    }
+                }
+                false
+            })
+            .collect();
+    }
+}