perf(coverage): faster source mapping (denoland#21783)

I did not measure this change (O(n) to O(log n)), but mainly this should
be slightly more accurate at getting the line number.

cli/tools/coverage/mod.rs

@@ -220,20 +220,11 @@ fn generate_coverage_report(
  continue;
  }
 
- let dest_line_index = text_lines.line_index(
- text_lines
- .byte_index_from_char_index(function.ranges[0].start_char_offset),
+ let line_index = range_to_src_line_index(
+ &function.ranges[0],
+ &text_lines,
+ &maybe_source_map,
  );
- let line_index = if let Some(source_map) = maybe_source_map.as_ref() {
- source_map
- .tokens()
- .find(|token| token.get_dst_line() as usize == dest_line_index)
- .map(|token| token.get_src_line() as usize)
- .unwrap_or(0)
- } else {
- dest_line_index
- };
-
  coverage_report.named_functions.push(FunctionCoverageItem {
  name: function.function_name.clone(),
  line_index,
@@ -244,18 +235,8 @@ fn generate_coverage_report(
  for (block_number, function) in script_coverage.functions.iter().enumerate() {
  let block_hits = function.ranges[0].count;
  for (branch_number, range) in function.ranges[1..].iter().enumerate() {
- let source_line_index = text_lines.line_index(
- text_lines.byte_index_from_char_index(range.start_char_offset),
- );
- let line_index = if let Some(source_map) = maybe_source_map.as_ref() {
- source_map
- .tokens()
- .find(|token| token.get_dst_line() as usize == source_line_index)
- .map(|token| token.get_src_line() as usize)
- .unwrap_or(0)
- } else {
- source_line_index
- };
+ let line_index =
+ range_to_src_line_index(range, &text_lines, &maybe_source_map);
 
  // From https://manpages.debian.org/unstable/lcov/geninfo.1.en.html:
  //
@@ -370,6 +351,24 @@ fn generate_coverage_report(
  coverage_report
 }
 
+fn range_to_src_line_index(
+ range: &cdp::CoverageRange,
+ text_lines: &TextLines,
+ maybe_source_map: &Option<SourceMap>,
+) -> usize {
+ let source_lc = text_lines.line_and_column_index(
+ text_lines.byte_index_from_char_index(range.start_char_offset),
+ );
+ if let Some(source_map) = maybe_source_map.as_ref() {
+ source_map
+ .lookup_token(source_lc.line_index as u32, source_lc.column_index as u32)
+ .map(|token| token.get_src_line() as usize)
+ .unwrap_or(0)
+ } else {
+ source_lc.line_index
+ }
+}
+
 fn collect_coverages(
  files: FileFlags,
 ) -> Result<Vec<cdp::ScriptCoverage>, AnyError> {