How do I get Summary to work?

I can’t get summary to work; the posts are shown in full.

One issue might be that summary.html is also in themes/theme-name/layout/_default/summary.html and that’s being used; but if I move /layouts/partials/summary.html to /layouts/_default/summary.html, and edit section.html to point to it, I get the error
can’t give argument to non-function “summary.html”

in config.toml I have summarylength = 20

/layouts/_default/list.html:

{{ define "main" }}
{{ $truncate := default true .Site.Params.truncate }}
{{ $paginator := .Paginate (where .Site.RegularPages "Section" "in" .Site.Params.mainSections) }}
{{ range $paginator.Pages }}
{{ if $truncate }}
{{ .Render "summary" }}
{{ else }}
{{ .Render "content" }}
{{ end }}
{{ end }}
{{ end }}

/layouts/_default/section.html:

{{ define "main" }}
  <main>
      {{ .Content }}
          <ul class="contents">
          {{ range .Paginator.Pages }}
              <li>{{.Title}}
                  <div>
                    {{ partial "summary.html" . }}
                  </div>
              </li>
          {{ end }}
          </ul>
      {{ partial "pagination.html" . }}
  </main>
{{ end }}

/layouts/partials/summary.html

<a href="{{ .Permalink }}">{{ .Title }}</a>

<p>{{.Summary}}</p>

<a href="{{ .Permalink }}">Read More</a>