Guarantee order of $f[opt-names] to match definition for function int…

…rospection.

Also augment the test of opt-names and opt-defaults to check that.

This fixes #1631.

pkg/eval/closure_test.elvts

@@ -34,10 +34,10 @@ Exception: unsupported options: bad1, bad2
 ▶ [a b]
 ~> put {|@r| }[rest-arg]
 ▶ 0
-~> put {|&opt=def| }[opt-names]
-▶ [opt]
-~> put {|&opt=def| }[opt-defaults]
-▶ [def]
+~> put {|&opt=def &opt2=def2 &opt0=def0| }[opt-names]
+▶ [opt opt2 opt0]
+~> put {|&opt=def &opt2=def2 &opt0=def0| }[opt-defaults]
+▶ [def def2 def0]
 ~> put { body }[body]
 ▶ 'body '
 ~> put {|x @y| body }[def]

website/ref/language.md

@@ -652,7 +652,8 @@ user-defined function, it has the following fields:
 -   `$f[rest-arg]` is the index of the rest argument. If there is no rest
     argument, it is `-1`.
 
--   `$f[opt-names]` is a list containing the names of the options.
+-   `$f[opt-names]` is a list containing the names of the options, in the order
+    they are defined in the source code.
 
 -   `$f[opt-defaults]` is a list containing the default values of the options,
     in the same order as `$f[opt-names]`.