message: Fix sourcemap.
  Closes
diff: @@ -78,7 +78,7 @@ impl<'a, W: Write> JsWriter<'a, W> {
  srcmap.add(
  self.line_count as _,
  self.line_pos as _,
  - loc.line as _,
  + (loc.line - 1) as _,
  loc.col.0 as _,
  src.as_ref().map(|s| &**s),
  None,
  