### Terraform Version ```shell Terraform v1.15.5 on linux_amd64 ``` ### Terraform Configuration Files ```terraform variable "null" { default = null const = true } module "main" { source = var.null } ``` ### Debug Output ``` 2026-06-07T22:59:56.318+0900 [INFO] Terraform version: 1.15.5 2026-06-07T22:59:56.318+0900 [DEBUG] using github.com/hashicorp/go-tfe v1.105.0 2026-06-07T22:59:56.318+0900 [DEBUG] using github.com/hashicorp/hcl/v2 v2.24.0 2026-06-07T22:59:56.318+0900 [DEBUG] using github.com/hashicorp/terraform-svchost v0.2.1 2026-06-07T22:59:56.318+0900 [DEBUG] using github.com/zclconf/go-cty v1.18.0 2026-06-07T22:59:56.318+0900 [INFO] Go runtime version: go1.25.10 2026-06-07T22:59:56.318+0900 [INFO] CLI args: []string{"terraform", "init"} 2026-06-07T22:59:56.318+0900 [DEBUG] Attempting to open CLI config file: /home/wata727/.terraformrc 2026-06-07T22:59:56.318+0900 [DEBUG] File doesn't exist, but doesn't need to. Ignoring. 2026-06-07T22:59:56.318+0900 [DEBUG] ignoring non-existing provider search directory terraform.d/plugins 2026-06-07T22:59:56.318+0900 [DEBUG] ignoring non-existing provider search directory /home/wata727/.terraform.d/plugins 2026-06-07T22:59:56.319+0900 [DEBUG] ignoring non-existing provider search directory /home/wata727/.local/share/terraform/plugins 2026-06-07T22:59:56.319+0900 [DEBUG] ignoring non-existing provider search directory /usr/local/share/terraform/plugins 2026-06-07T22:59:56.319+0900 [DEBUG] ignoring non-existing provider search directory /usr/share/terraform/plugins 2026-06-07T22:59:56.319+0900 [DEBUG] ignoring non-existing provider search directory /var/lib/snapd/desktop/terraform/plugins 2026-06-07T22:59:56.319+0900 [INFO] CLI command args: []string{"init"} Initializing modules... 2026-06-07T22:59:56.323+0900 [DEBUG] ReferenceTransformer: "var.null" references: [] 2026-06-07T22:59:56.323+0900 [DEBUG] ReferenceTransformer: "module.main" references: [var.null] 2026-06-07T22:59:56.323+0900 [DEBUG] Starting graph walk: walkInit 2026-06-07T22:59:56.324+0900 [ERROR] vertex "module.main" panicked !!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!! Terraform crashed! This is always indicative of a bug within Terraform. Please report the crash with Terraform[1] so that we can fix this. When reporting bugs, please include your terraform version, the stack trace shown below, and any additional information which may help replicate the issue. [1]: https://github.com/hashicorp/terraform/issues !!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!! panic: value is null goroutine 49 [running]: runtime/debug.Stack() runtime/debug/stack.go:26 +0x5e github.com/hashicorp/terraform/internal/logging.PanicHandler() github.com/hashicorp/terraform/internal/logging/panic.go:84 +0x16a panic({0x3bfc8e0?, 0x4da74f0?}) runtime/panic.go:783 +0x132 github.com/hashicorp/terraform/internal/terraform.(*Graph).walk.func1.1() github.com/hashicorp/terraform/internal/terraform/graph.go:59 +0x4e5 panic({0x3bfc8e0?, 0x4da74f0?}) runtime/panic.go:783 +0x132 github.com/zclconf/go-cty/cty.Value.AsString({{{0x4e11b98?, 0x4d9ad90?}}, {0x0?, 0x0?}}) github.com/zclconf/go-cty@v1.18.0/cty/value_ops.go:1461 +0x10b github.com/hashicorp/terraform/internal/terraform.evalSource({0x4e124d8, 0xc000c00900}, 0x0, {0x4e4e6a0, 0xc000c1c360}) github.com/hashicorp/terraform/internal/terraform/node_module_install.go:217 +0x539 github.com/hashicorp/terraform/internal/terraform.(*nodeInstallModule).Execute(0xc0006d41e0, {0x4e4e6a0, 0xc000c1c360}, 0x58?) github.com/hashicorp/terraform/internal/terraform/node_module_install.go:94 +0x2b1 github.com/hashicorp/terraform/internal/terraform.(*ContextGraphWalker).Execute(0xc000788840, {0x4e4e6a0, 0xc000c1c360}, {0x7a49d5312bf0, 0xc0006d41e0}) github.com/hashicorp/terraform/internal/terraform/graph_walk_context.go:170 +0xaf github.com/hashicorp/terraform/internal/terraform.(*Graph).walk.func1({0x4151480, 0xc0006d41e0}) github.com/hashicorp/terraform/internal/terraform/graph.go:143 +0x755 github.com/hashicorp/terraform/internal/dag.(*Walker).walkVertex(0xc0006f8ae0, {0x4151480, 0xc0006d41e0}, 0xc0006da200) github.com/hashicorp/terraform/internal/dag/walk.go:393 +0x2d1 created by github.com/hashicorp/terraform/internal/dag.(*Walker).Update in goroutine 1 github.com/hashicorp/terraform/internal/dag/walk.go:316 +0xf13 ``` ### Expected Behavior It should result in an error, similar to https://github.com/hashicorp/terraform/pull/38628 ### Actual Behavior It will cause panic. ### Steps to Reproduce 1. `terraform init` ### Additional Context `value.AsString() will cause a panic for marked values. This is the same issue as https://github.com/hashicorp/terraform/issues/38694. `value.AsString()` causes a panic for null values. https://github.com/zclconf/go-cty/blob/v1.18.0/cty/value_ops.go#L1460-L1462 The https://github.com/hashicorp/terraform/pull/38628 fix does not account for the case where the value after evaluation is null. Just to be clear, this issue did not occur in actual production code. It was discovered during white-box testing when [supporting dynamic module sources in TFLint](https://github.com/terraform-linters/tflint/pull/2521), and such cases are likely to be rare in practice. ### References - https://github.com/hashicorp/terraform/pull/38217 - https://github.com/hashicorp/terraform/pull/38628 ### Generative AI / LLM assisted development? _No response_