terraform test panics ("value has marks") when a failed assertion references a whole object that has deprecated attributes

Finding: In an external report, terraform test on Terraform v1.17.0-rc1 (also reported on v1.16.2 and v1.16.5, hashicorp/aws v6.68.0, darwin_arm64) panics instead of printing the assertion message when a failing assert condition references a whole data source object whose schema has deprecated attributes. The panic message is about marshalling a value with marks that cannot be serialized as JSON; the run is marked fail and the process exits 11 [https://github.com/hashicorp/terraform/issues/39365]. Reported reproduction: a mock_provider "aws" test with data.aws_iam_policy_document.this and a failing condition such as [data.aws_iam_policy_document.this][0].id == "never-matches". The stack trace places the panic in views/json NewDiagnostic (diagnostic.go:278) while the human test view formats diagnostics. The reporter says it also happens with the real AWS provider using dummy credentials, so mocking is not required [https://github.com/hashicorp/terraform/issues/39365]. Reporter's matrix: direct attribute references (data.aws_iam_policy_document.this.id) and length(...statement) failed cleanly with exit 1. Whole-object shapes such as the bracket-wrapped reference, a for expression over the object, and the same over for_each instance maps panicked with exit 11. for_each maps of terraform_data, data.local_file and a mocked aws_sns_topic failed cleanly [https://github.com/hashicorp/terraform/issues/39365]. Cause status: the reporter assumes the deprecation marks on override_json and source_json are what cannot be serialized; this is a hypothesis, not maintainer-confirmed [https://github.com/hashicorp/terraform/issues/39365]. The report links #39239 as a similar panic on a deprecated azurerm resource, reportedly closed as not planned pending a re-check; closure is not evidence of a fix. Status: the issue is open, with no maintainer response or fix/release link in the supplied content. The CI exit is non-zero, so the failure is still visible, but the diagnostic is lost. Possible mitigation (source-backed, not verified by KFA): in the reporter's matrix, assertions that reference specific attributes rather than the whole object failed cleanly. This is an observation, not a maintainer-endorsed workaround. Limitations: this is a single external report with disclosed AI assistance, not reproduced by KFA and with no independent reproduction. Comments may be incomplete. Scope beyond the tested resources is unknown.