From 7162e79fdf8fc24be62371eb1d800d24e837cf19 Mon Sep 17 00:00:00 2001
From: Katy Moe <katy@katy.moe>
Date: Mon, 15 Nov 2021 10:43:06 +0000
Subject: [PATCH] return error on resource type mismatch

A resource move is invalid if the two resource( instance)s are of different
resource types. Check for this during move validation.
---
 internal/refactoring/move_validate.go | 36 +++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/internal/refactoring/move_validate.go b/internal/refactoring/move_validate.go
index 2c38ba756d..b59bc315ef 100644
--- a/internal/refactoring/move_validate.go
+++ b/internal/refactoring/move_validate.go
@@ -178,6 +178,16 @@ func ValidateMoves(stmts []MoveStatement, rootCfg *configs.Config, declaredInsts
 				}
 			}
 
+			// Resource types must match.
+			if resourceTypesDiffer(absFrom, absTo) {
+				diags = diags.Append(&hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Resource type mismatch",
+					Detail: fmt.Sprintf(
+						"This statement declares a move from %s to %s, which is a %s of a different type.", absFrom, absTo, noun,
+					),
+				})
+			}
 		}
 	}
 
@@ -238,6 +248,32 @@ func moveableObjectExists(addr addrs.AbsMoveable, in instances.Set) bool {
 	}
 }
 
+func resourceTypesDiffer(absFrom, absTo addrs.AbsMoveable) bool {
+	switch absFrom.(type) {
+	case addrs.AbsResourceInstance, addrs.AbsResource:
+		// addrs.UnifyMoveEndpoints guarantees that both addresses are of the
+		// same kind, so at this point we can assume that absTo is an
+		// addrs.AbsResourceInstance or addrs.AbsResource.
+		return absMoveableResourceType(absFrom) != absMoveableResourceType(absTo)
+	default:
+		return false
+	}
+}
+
+// absMoveableResourceType returns the type of the supplied
+// addrs.AbsResourceInstance or addrs.AbsResource, or "" for other AbsMoveable
+// types.
+func absMoveableResourceType(addr addrs.AbsMoveable) string {
+	switch addr := addr.(type) {
+	case addrs.AbsResourceInstance:
+		return addr.Resource.Resource.Type
+	case addrs.AbsResource:
+		return addr.Resource.Type
+	default:
+		return ""
+	}
+}
+
 func movableObjectDeclRange(addr addrs.AbsMoveable, cfg *configs.Config) (tfdiags.SourceRange, bool) {
 	switch addr := addr.(type) {
 	case addrs.ModuleInstance: