docs(_comp_compgen): clarify @return

Author: akinomyoga

bash_completion

@@ -453,6 +453,8 @@ _comp_compgen__error_fallback()
 #
 #   Note: The array option `-V arr` in bash >= 5.3 should be instead specified
 #   as `-v arr` as a part of the `_comp_compgen` options.
+# @return  True (0) if at least one completion is generated, False (1) if no
+#   completion is generated, or 2 with an incorrect usage.
 #
 # Usage #2: _comp_compgen [-alR|-v arr|-c cur] name args...
 # Call the generator `_comp_compgen_NAME ARGS...` with the specified options.
@@ -470,6 +472,7 @@ _comp_compgen__error_fallback()
 #   These variables are internally used to pass the effect of the options
 #   [-alR|-v arr|-c cur] to the child calls of `_comp_compgen` in
 #   `_comp_compgen_NAME`.
+# @return   Exit status of the generator.
 #
 # @remarks When no options are supplied to _comp_compgen, `_comp_compgen NAME
 # args` is equivalent to the direct call `_comp_compgen_NAME args`.  As the