tpl/collections: Improve error message in Index

diff --git a/tpl/collections/index.go b/tpl/collections/index.go
index d72d3748fcaafe9d1b9d0be881dad68bf20e80f2..e4362fdc39dffb00cf8a7519b2b1aa6407cb98c9 100644 (file)
--- a/tpl/collections/index.go
+++ b/tpl/collections/index.go
@@ -31,6 +31,14 @@ import (
 //
 // We deviate from the stdlib mostly because of https://github.com/golang/go/issues/14751.
 func (ns *Namespace) Index(item any, args ...any) (any, error) {
+       v, err := ns.doIndex(item, args...)
+       if err != nil {
+               return nil, fmt.Errorf("index of type %T with args %v failed: %s", item, args, err)
+       }
+       return v, nil
+}
+
+func (ns *Namespace) doIndex(item any, args ...any) (any, error) {
        // TODO(moorereason): merge upstream changes.
        v := reflect.ValueOf(item)
        if !v.IsValid() {