gohugoio/hugo · error

can't iterate over {type}

Error message

can't iterate over {type}

What it means

After (collections.go:85-90) accepts only reflect.Array, Slice, or String. Any other Kind (map, struct, int, etc.) reaches the default branch and reports the actual type.

Source

Thrown at tpl/collections/collections.go:89

	if err != nil {
		return nil, err
	}

	if nv < 0 {
		return nil, errors.New("sequence bounds out of range [" + cast.ToString(nv) + ":]")
	}

	lv := reflect.ValueOf(l)
	lv, isNil := hreflect.Indirect(lv)
	if isNil {
		return nil, errors.New("can't iterate over a nil value")
	}

	switch lv.Kind() {
	case reflect.Array, reflect.Slice, reflect.String:
		// okay
	default:
		return nil, errors.New("can't iterate over " + reflect.ValueOf(l).Type().String())
	}

	if nv >= lv.Len() {
		return lv.Slice(0, 0).Interface(), nil
	}

	return lv.Slice(nv, lv.Len()).Interface(), nil
}

// Delimit takes a given list l and returns a string delimited by sep.
// If last is passed to the function, it will be used as the final delimiter.
func (ns *Namespace) Delimit(ctx context.Context, l, sep any, last ...any) (string, error) {
	d, err := cast.ToStringE(sep)
	if err != nil {
		return "", err
	}

	var dLast *string

View on GitHub (pinned to 52c9bd7908)

Solutions

1. Pass a slice/array/string, not a map or scalar
2. If you have a map, extract a slice first (e.g. its values or a known sub-collection)
3. Use .Pages instead of .Page for collections

Example fix

// before
{{ after 2 .Params }}
// after
{{ after 2 .Pages }}

{{ if reflect.IsSlice .Pages }}
  {{ after 2 .Pages }}
{{ end }}

{{/* Go-side */}}
func isIteratable(v any) bool {
  k := reflect.TypeOf(v).Kind()
  return k == reflect.Slice || k == reflect.Array || k == reflect.String
}

When it happens

Trigger: {{ after 2 .Site.Data }} (map), {{ after 2 42 }} (int), {{ after 2 .Page }} (struct).

Common situations: Passing a dict/params map where a slice was expected; passing a single Page object instead of a page collection; passing a number.

Related errors

• called apply using {xt} as type {targ}
• invalid dictionary key
• intersect does not support slices or arrays of uncomparable
• need at least 2 arguments to append
• can't apply myself (no turtles allowed)

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/048d52dde38536d0. Report an issue: GitHub.