I can access {{ uri.params }} in a Twig template, but if I try something like
{{ uri.param[‘location’] }}
as documented at http://learn.getgrav.org/themes/theme-vars
I get an error.

Any idea what I am doing wrong?

Oh, I figured this out! There is an error in the docs…
uri.param[‘param’] = foo
should be something like:
uri.param[(‘category’’) = foo
(parens instead of brackets)

Help a brother out by submitting a pull request on the docs with the fix?