Address review comments

Author: petrochenkov

src/libsyntax/parse/parser.rs

@@ -1884,7 +1884,9 @@ impl<'a> Parser<'a> {
  Ok(())
  }
 
- // Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
+ /// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
+ /// Attempt to convert the base expression/pattern/type into a type, parse the `::AssocItem`
+ /// tail, and combine them into a `<Ty>::AssocItem` expression/pattern/type.
  fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: P<T>, allow_recovery: bool)
  -> PResult<'a, P<T>> {
  // Do not add `::` to expected tokens.
@@ -1896,6 +1898,8 @@ impl<'a> Parser<'a> {
  Ok(base)
  }
 
+ /// Given an already parsed `Ty` parse the `::AssocItem` tail and
+ /// combine them into a `<Ty>::AssocItem` expression/pattern/type.
  fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(&mut self, ty_span: Span, ty: P<Ty>)
  -> PResult<'a, P<T>> {
  self.expect(&token::ModSep)?;
@@ -1912,7 +1916,7 @@ impl<'a> Parser<'a> {
  path.span, "try", format!("<{}>::{}", ty_str, path), Applicability::MaybeIncorrect
  ).emit();
 
- let path_span = path.span.to(path.span); // use an empty path since `position` == 0
+ let path_span = ty_span.shrink_to_hi(); // use an empty path since `position` == 0
  Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
  }