Merge pull request #28126 from hashicorp/alisdair/validate-traversal-caveat

documentation: Clarify JSON diagnostic values traversal semantics

website/docs/cli/commands/validate.html.md

@@ -202,7 +202,11 @@ part of the expression which triggered the diagnostic. This is especially
 useful when using `for_each` or similar constructs, in order to identify
 exactly which values are responsible for an error. The object has two properties:
 
-* `traversal` (string): An HCL traversal string, such as `var.instance_count`.
+* `traversal` (string): An HCL-like traversal string, such as
+  `var.instance_count`. Complex index key values may be elided, so this will
+  not always be valid, parseable HCL. The contents of this string are intended
+  to be human-readable and are subject to change in future versions of
+  Terraform.
 
 * `statement` (string): A short English-language fragment describing the value
   of the expression when the diagnostic was triggered. The contents of this