Merge pull request #10887 from dvandersluis/lint/shadowed-exception

Improve documentation for `Lint/ShadowedException`

lib/rubocop/cop/lint/shadowed_exception.rb

@@ -7,6 +7,14 @@ module Lint
       # less specific exception being rescued before a more specific
       # exception is rescued.
       #
+      # An exception is considered shadowed if it is rescued after its
+      # ancestor is, or if it and its ancestor are both rescued in the
+      # same `rescue` statement. In both cases, the more specific rescue is
+      # unnecessary because it is covered by rescuing the less specific
+      # exception. (ie. `rescue Exception, StandardError` has the same behavior
+      # whether `StandardError` is included or not, because all `StandardError`s
+      # are rescued by `rescue Exception`).
+      #
       # @example
       #
       #   # bad
@@ -19,6 +27,13 @@ module Lint
       #     handle_standard_error
       #   end
       #
+      #   # bad
+      #   begin
+      #     something
+      #   rescue Exception, StandardError
+      #     handle_error
+      #   end
+      #
       #   # good
       #
       #   begin