@@ -197,31 +197,45 @@ impl CodeSuggestion {
197197
198198 use rustc_span:: { CharPos , Pos } ;
199199
200- /// Append to a buffer the remainder of the line of existing source code, and return the
201- /// count of lines that have been added for accurate highlighting.
200+ /// Extracts a substring from the provided `line_opt` based on the specified low and high indices,
201+ /// appends it to the given buffer `buf`, and returns the count of newline characters in the substring
202+ /// for accurate highlighting.
203+ /// If `line_opt` is `None`, a newline character is appended to the buffer, and 0 is returned.
204+ ///
205+ /// ## Returns
206+ ///
207+ /// The count of newline characters in the extracted substring.
202208fn push_trailing (
203209 buf : & mut String ,
204210 line_opt : Option < & Cow < ' _ , str > > ,
205211 lo : & Loc ,
206212 hi_opt : Option < & Loc > ,
207213 ) -> usize {
208214 let mut line_count = 0 ;
215+ // Convert CharPos to Usize, as CharPose is character offset
216+ // Extract low index and high index
209217 let ( lo, hi_opt) = ( lo. col . to_usize ( ) , hi_opt. map ( |hi| hi. col . to_usize ( ) ) ) ;
210218 if let Some ( line) = line_opt {
211219 if let Some ( lo) = line. char_indices ( ) . map ( |( i, _) | i) . nth ( lo) {
220+ // Get high index while account for rare unicode and emoji with char_indices
212221 let hi_opt = hi_opt. and_then ( |hi| line. char_indices ( ) . map ( |( i, _) | i) . nth ( hi) ) ;
213222 match hi_opt {
223+ // If high index exist, take string from low to high index
214224 Some ( hi) if hi > lo => {
225+ // count how many '\n' exist
215226 line_count = line[ lo..hi] . matches ( '\n' ) . count ( ) ;
216227 buf. push_str ( & line[ lo..hi] )
217228 }
218229 Some ( _) => ( ) ,
230+ // If high index absence, take string from low index till end string.len
219231 None => {
232+ // count how many '\n' exist
220233 line_count = line[ lo..] . matches ( '\n' ) . count ( ) ;
221234 buf. push_str ( & line[ lo..] )
222235 }
223236 }
224237 }
238+ // If high index is None
225239 if hi_opt. is_none ( ) {
226240 buf. push ( '\n' ) ;
227241 }
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